Alluminum Heads

[holorinhal]

Hey Fellers It's Me again.
Iwould like to hear Your opinion's on brand's and type's of alluminum heads.
I have decided to take the plunge and purchase a set of alluminum heads for My 454 stroker(489).
My question is ,what do You think the best head is for the money,Edelbrock,Brodix,World Merlin,AFR or TrickFlow?
I know some of You guy's are running allum.head's.What head's are You running and what do You like about them.
I do not have unlimited resourse's(cash),so I am looking for the best bang for the buck!Thank's for You'r input....Hal

[MACHINEHEAD]

These are a little spendy but I would run the AFR305 w/cnc chamber option
They will net you 645hp/615lbs W/victor jr. and 850. And dare I say a cam
W/245-250@.050 intake and 248-253@.050 exhaust. 112lda And .570-.640lift
You better have headers. Contact me if you need a set. I'll check them out for spring preasure/clearences ect. for you.
This is cool you sure know how to stir a pot.!!

[JAY4SPEED]

If you order the AFRs, make sure you tell them its for marine use before they start to machine the heads. They can be treated for marine use, but it needs to be done before they machine them.
Jay

[lilrick]

you said,"most bang for your buck". so I definitely would stay away from aluminum! Is this a race deal or pleasure? how much horsepower are you trying to achieve???

[flat broke]

you said,"most bang for your buck". so I definitely would stay away from aluminum! Is this a race deal or pleasure? how much horsepower are you trying to achieve???
Why stay away from aluminum. HP potential to total $$ spent, a new pair of aluminum heads typically will beat out a set of 990s or 049s. Sure if the guy is going to run a flat tappet hyd. cam, then might as well not waste your money on a head that will never see the flow. But if he is going to step up to a decent roller profile, he might as well spend the smart money on a set of heads.
The late model GM rectangle ports and Word cast Iron heads use a false seat that is notorious for dropping in marine application. So what if you can score em cheap when they pose a greater risk of failure and taking out your engine.
If you try and go with some older heads, you have to have em checked out $$$. Many of them have been ported to death, and have excessively large chambers, or worse, thin domes or deck mating surfaces from being reworked numerous times, which will ultimately lead to a cracked head and again, possible engine damage. By the time it is all said and done, spending good money on a good set of heads, is always a better investment than spending less money on a used set of iron heads thats been around the block, only to either suffer a loss of HP compared to the same motor with better heads, or worse, have to turn around and buy the aluminum heads after you've dumped the money into the iron set in the first place. Buy once, Cry once.
Additionally:
holorinhal, you should definitely think about adding the Canfield 310 to your list of possible heads. There are also other CNC port sizes available depending on what compression ratio you want to end up with. I'm running them on a 498 and am nothing but happy with em!
Chris

[BAE_557]

What about a set of Dart 360's, those worked great for me in the past.

[Squirtcha?]

Why stay away from aluminum. HP potential to total $$ spent, a new pair of aluminum heads typically will beat out a set of 990s or 049s. Sure if the guy is going to run a flat tappet hyd. cam, then might as well not waste your money on a head that will never see the flow. But if he is going to step up to a decent roller profile, he might as well spend the smart money on a set of heads.
If you try and go with some older heads, you have to have em checked out $$$. Many of them have been ported to death, and have excessively large chambers, or worse, thin domes or deck mating surfaces from being reworked numerous times, which will ultimately lead to a cracked head and again, possible engine damage. By the time it is all said and done, spending good money on a good set of heads, is always a better investment than spending less money on a used set of iron heads thats been around the block, only to either suffer a loss of HP compared to the same motor with better heads, or worse, have to turn around and buy the aluminum heads after you've dumped the money into the iron set in the first place. Buy once, Cry once.
Chris
Somewhat off topic but........
Having "been there, done that" I'd have to agree with most everything Chris has stated here. I had a set of BBF iron DOVE heads worked over by a guy (supposed professional) and he removed too much material in porting process. Both heads cracked by a valve guide on their first outing. I paid close to a grand to have the work done. Rather than find another set to be reworked by another "professional" I picked up a set of Edelbrock aluminums for $1600 all loaded up with valves, springs etc. and ready to bolt on.
I'm still running a flat tappet hydraulic cam and probably not getting the full benefit of the heads, but they're working just fine for my purposes. Personally, I'd never spend the money on another set of iron heads when there are so many competitively priced aluminum ones available. Also very nice to shave about 60-70 lbs of weight.
I'm sure that the iron heads can be made to work fine by someone who truly knows what they're doing. I just wouldn't want to gamble on it again.

[steelcomp]

You're not going to get a better head for your money than the Canfields. You can spend more, and get more, but for the $, they have the best numbers for their port size, and unless you're building an all out racing motor, you don't need more.
Typically, across the board, you're going to make anywhere from 5-8 more hp with iron heads with the same flow numbers and characteristics, than what you will with aluminum. That's just a proven fact.
A 360cc port would be way too big in a jet boat for this motor. Stick with something under 320cc's.

[Wally_Gator]

Typically, across the board, you're going to make anywhere from 5-8 more hp with iron heads with the same flow numbers and characteristics, than what you will with aluminum. That's just a proven fact.
I am curious as to why iron will make more hp versus alum?
What are the physical properties that make this possable?
Does anyone know the answer to these questions?

[BrendellaJet]

I think Hotrod did a test on this in the last few months(may have been Car Craft or Chevy High Performance too) On their specific combo aluminum and iron performed the same, well over 10:1 too. Apples for Apples comparison I believe. Didn't detonate either with the iron. Not that that should end the long argued"aluminum allows more compression" debate, nor the "iron holds more heat and makes more power", but on their test engine they were equal. All I know is aluminum is a lot lighter and you will benefit from that in a jet boat.

[Squirtcha?]

I subscribe to CarCraft and I read that article as well. Who's to say that the outcome would be the same with different motors and configurations, but they did say in that particular test the only difference between the two small block Chevys was the weight factor.

[Sleek-Jet]

I've been kicking around the idea of putting the Dart Iron Eagle package on the boat when it's time... don't know if that's a good idea or not.

[bottom feeder]

I went with the Canfield Heads. No comparing to the old 049's

[77charger]

we had pro toplines and they worked well.Hard to find though.Also use canfields and they seem to work good also.

[77charger]

I am curious as to why iron will make more hp versus alum?
What are the physical properties that make this possable?
Does anyone know the answer to these questions?
Usually alm heads come pocket ported.
Just cause they are alm they dont make any more power.If both alm and iron heads were not touched hp would be the same,But alm can take a lil more compresion without detonation which can make a lil more hp
Alm will disapate heat faster,which help keep detonation away when heated up.Which is why you can run a lil more compression on the same octane gas.In a boat motor usually you run pretty cool and an iron head can reatian heat better in the combustion chamber vs alm but if too warm you are steppin backwards.
IMO use alm in a race boat for the weight savings and iron in a lake boat.My reason is that alm heads if heated up really hot can or will warp,corrosion is or can be a factor.The difference in hp probably wont be felt vs in a race application where everything matters weight and hp

[Squirtcha?]

Alm will dissipate heat faster,which help keep detonation away when heated up.Which is why you can run a lil more compression on the same octane gas.In a boat motor usually you run pretty cool and an iron head can retain heat better in the combustion chamber vs alm but if too warm you are stepping back wards.
This is exactly what Car Craft was talking about (and everyone has heard and repeated for years) hell I've even parroted those words myself. It's what they're saying they were unable to duplicate on a dyno with identical engines save for the iron vs. aluminum head deal. No more prone to detonate with iron than aluminum, and no more or less power with either head.
Once again, not to say that the rag is infallible or it's the gospel and will always be true no matter what type, or size engine, or compilation of parts is used.
It was just their finding on this one particular test and article.

[steelcomp]

I am curious as to why iron will make more hp versus alum?
What are the physical properties that make this possable?
Does anyone know the answer to these questions?
There's always been a lot of discussion about this, and there are various reasons why it's thought this occurs, but it is fact. Some of the reasons are as follows.
Aluminum expands and contracts, and as aluminum heads expand with heat, things change. Valve lash, combustion chamber shape, valve train dynamics change, etc. Basically, the heads are not as rigid, and don't hold their shape. The decks tend to leak slightly, so there's some cyl. pressure loss. Compression is reduced by the expanding chamber. Cyl pressure is absorbed in the expanding aluminum. Guides can move, and valves may not seal perfectly. On and on.
There is also the theory of thermal loss through the aluminum. Some have tried to verify this by stating better power with coated pistons and chambers, (with aluminum heads) retaining the heat better. Cast iron definately reflects more heat back into the chamber, which will always equal more hp. I'm not sure I buy the thermal loss theory with aluminum as much as just in general, aluminum won't hold it's shape as well as iron. It's a known fact that a motor built with an aluminum block can lose as much as 50 hp over a motor with a good cast iron block. Iron block is more rigid, the bores stay rounder, the block flexes less, etc. Seems to me the same might hold true for the cast iron vs. alum head. However, you're definately limited to port and chamber design when it comes to cast iron, so the HP difference may very well be offset by the weight savings, especially with a big block.
Hope that helps.

[hallnass]

I pick the Dart Pro 1 cnc 355. you should be able to make around 800hp with
high compression and a good solid roller. These are about the best 23 degree
heads on the market right now. If you want to see some in action go to
youngbloodjetboats.com and look under the video links you will find some
good runs.
Keith :skull:

[MACHINEHEAD]

Dont discount flat tappets. A better head is a better head no matter what type of cam. The Canfield 310 with cnc chamber is down 35hp to the AFR305cnc chamber on the same combo 489.Same torque though 615ft/lb. Canfields can be had in this configuration for about $1600 complete versus $2349 for the AFR. I recomended the Canfield to my good friend whom I built the 489. Come to find out later the AFR was just better. He still hasnt stepped up to the plate for that extra 35hp, and why should he, 30 degrees of air temp will offset the loss of $750 dollars. And the reason why that test didnt show a difference is because they didnt push the aluminum head to 10.8 to one!

[Jspeeddemon]

A set of Dart 355 were pulled off my buddies boat and taken to the flow bench in as is condition. They were very impressive all the way through the curve, flowed 404 @.700 on the intake and 290@.700 on the exhaust. The motor made 875hp @13.5:1, with a relatively moderate cam for that cubic inch motor. We are switching two motors both 588's to the AFR 357 CNC, will let you know the reults here shortly.
Also the older heads from GM and even the new GM aluminum heads are crap on the exhaust side, it would be very difficult to make big power with GM heads, even the new ones. Look at Edelbrocks site for the flow numbers on the new GM heads.

[MACHINEHEAD]

Hal is puttin together a ski/pleasure jet with a warmed up jaccuzi on pump gas. But you should see about 60-80hp if your cam is at least 275@.050 with the AFR. AT LEAST!!!

[holorinhal]

If I am understanding right,some are of the opinion that the benifit of hp gain from aluminum heads come from high compretion ratio engines.
My motor has 10.5:1 compretion ratio,while is above standard,it still is'nt considered a high compretion engine?
Will i benifit with a gain in hp,or is the benifit simply a better head over the iorn head,and a decrease in weight.
Squirtcha,what comp ratio is You'r engine running and did You see an increase in hp ,with the edelbrock head's,over the iorn heads?...Hal

[Squirtcha?]

I'm running a very conservative 9:1 compression ratio. I wanted to be able to run on regular 87 octane pump gas, and I can if I bump the timing back a little bit. Typically I run 91 octane though (especially when using the nitrous).
It's difficult to say if there was an increase in horsepower. My reworked iron heads didn't last long enough to get a good run in, and that motor had other problems going on besides the heads.
I'm probably not getting the full benefit of the heads flow capabilities due to a mild cam .244 duration .577 lift at .050 flat tappet hydraulic with a 110CL, coupled with the low compression.
Still.........all in all, very happy with the heads so far. They were a bolt on proposition and I haven't had to mess with em in the three years I've run em.
The nice part of the deal is, if I want to change pistons for more compression, and put in a bigger mechanical camshaft, the heads will support that. May have to get some port work done and put in some different springs, but that'd be about it.
Honestly, the main reason I went with the Ebrocks was price. I looked at others, and knowing what I wanted from my motor, these were going to fit the bill just fine. I believe I paid $1650 for the pair including tax delivery etc. That was for the complete and ready to bolt on set. Not sure what they're selling for now.

[MACHINEHEAD]

The deal is Hal, you have to go aluminum if you want to run pump gas, period.

[holorinhal]

Machinehead, Why is it that aluminum heads are required ,to run pump gas?
Please explain.

[steelcomp]

Machinehead, Why is it that aluminum heads are required ,to run pump gas?
Please explain.Yeah, I'd really like to hear this one. :rolleyes:

[steelcomp]

Dont discount flat tappets. A better head is a better head no matter what type of cam. The Canfield 310 with cnc chamber is down 35hp to the AFR305cnc chamber on the same combo 489.Same torque though 615ft/lb. Canfields can be had in this configuration for about $1600 complete versus $2349 for the AFR. I recomended the Canfield to my good friend whom I built the 489. Come to find out later the AFR was just better. He still hasnt stepped up to the plate for that extra 35hp, and why should he, 30 degrees of air temp will offset the loss of $750 dollars. And the reason why that test didnt show a difference is because they didnt push the aluminum head to 10.8 to one!
To compare power numbers between the Can's and the AFR's on the same motor, same combination, is useless. All you're proving is that the combination was better suited for the AFR's than the Canfields, not that the AFR's were better heads.
A better head is a better head no matter what type of cam. That all depends. One head can be made to work as good as another, depending on the cam. For comparable heads, like your comparison between the Can 310's and the AFR's, either can work as well. They both have completely different flow characteristics, and would require completely different cams, to get the most out of either. Unless the CFM requirement is at the top of the head's capacity, either will work as well. One thing I DON'T like about the AFR's, is that all their flow numbers are done on a 4.600 bore fixture. Can, and most others use a 4.500. But, hey, when all you want is to be able to brag about numbers, then by all means, buy the AFR's. I'll take that extra $750.00 and use it better, somewhere else.
He still hasnt stepped up to the plate for that extra 35hp, and why should he, 30 degrees of air temp will offset the loss of $750 dollars
So, won't that 30 deg. of air temp effect the heads equally? This dosen't make sense.
I'm also curious, at what RPM was that 35 hp difference?
And the reason why that test didnt show a difference is because they didnt push the aluminum head to 10.8 to one![/QUOTE]You said there was a 35 hp difference, and what do you mean by "push the aluminum head to 10.8:1"??

[MACHINEHEAD]

You are correct the AFR is a better head for this specific combo. I like to make it easy on myself and use off the shelf cams and head/manifold combos.As soon as you say pump gas everything is a comprimise.I dont want to spend all day at the dyno to try and make the Canfields work,Ive got engines to build.

[flat broke]

You are correct the AFR is a better head for this specific combo. I like to make it easy on myself and use off the shelf cams and head/manifold combos.As soon as you say pump gas everything is a comprimise.I dont want to spend all day at the dyno to try and make the Canfields work,Ive got engines to build.
The thing about that is you don't need to spend all day and all night on the dyno to make the Canfields "work". They work right out of the box. If you mean to get the most out of them, or any other head for that matter; that is less a function of time on the dyno, and more a function of understanding the flow characteristics and velocities of the head. Then ordering a cam with the proper grind and lobe profiles to take advantage/cater to the flow characteristics of the head. ;)
Chris

[MACHINEHEAD]

The Canfield will always be down on power compaired to the AFR, no matter what temp. I was attempting to explain how 35hp would probably not be felt in the real word, due to temp changes. Basicaly the Canfield will run like the AFR when its 60deg. And the AFR will run like the Canfield when its 100deg. Sorry for the confusion. If these test motors made the same HP with both heads and the same comp ratio and didnt detonate, then they didnt try hard enough to push the aluminum head. It would have made more power if it was pushed to the limit of detonation. Thats all.

[bumpstik]

h-hal: The al. heads are a requirement for pump gas, because @ 10-10.5:1 with iron heads you are either lightly detonating all of the time or the first time your 91 oct. "river gas" is more like 87-you will melt a piston.The al head will not ping @ 10.8 or so.

[HBjet]

h-hal: The al. heads are a requirement for pump gas, because @ 10-10.5:1 with iron heads you are either lightly detonating all of the time or the first time your 91 oct. "river gas" is more like 87-you will melt a piston.The al head will not ping @ 10.8 or so.
Currently running 10.250:1 with Iron 990's... Use pump gas all the time for 3 years now and 98% of the time all the gas has been purchased at the river (in town) Never had a problem :rolleyes:
HBjet

[steelcomp]

The Canfield will always be down on power compaired to the AFR, no matter what temp. I was attempting to explain how 35hp would probably not be felt in the real word, due to temp changes. Basicaly the Canfield will run like the AFR when its 60deg. And the AFR will run like the Canfield when its 100deg. Sorry for the confusion. If these test motors made the same HP with both heads and the same comp ratio and didnt detonate, then they didnt try hard enough to push the aluminum head. It would have made more power if it was pushed to the limit of detonation. Thats all.So what causes gasoline to detonate??

[steelcomp]

The thing about that is you don't need to spend all day and all night on the dyno to make the Canfields "work". They work right out of the box. If you mean to get the most out of them, or any other head for that matter; that is less a function of time on the dyno, and more a function of understanding the flow characteristics and velocities of the head. Then ordering a cam with the proper grind and lobe profiles to take advantage/cater to the flow characteristics of the head. ;)
Chris
Couldn't have said it better myself. Besides, there are a ton of factors effecting power than just heads and cam. Flow numbers are like HP...kinda, so what. Just numbers for reference, not much more.

[MACHINEHEAD]

I have spent alot of time pushing the envelope of pump gas engines. I know what detonation is and the things that cause it. I do this for a living. You can TALK about it all day long . I'll still be working on new combos, pushing the envelope,custom ordering cams that really dont change hp/trq enough to even bother ordering. Once you guys figure out that pump gas is a comprimise in its self, you might stop yacking about custom grinds/air flow bla bla bla. All of these little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor that puts out 1.3 hp/ci. So build your favorite pump gas motor and prove it to yourselves. Hey Hal, I like the AFRs and the previously mentioned cam.

[steelcomp]

So what causes gasoline to detonate?

[MACHINEHEAD]

What is Pre-Ignition? What is a Fuel Kernel ? What is BMEP ? Go read a book, You will get the answers

[Squirtcha?]

Don't want to get in the middle of this, but I will say one thing. I know of at least 3 motors that get run real hard at the river or lake (Randy's being one of em). They're all running in the upper 90 mph range and are out being pounded on just about every weekend. They're all pushing 725+ hp and doing it on pump gas.
Like I said, I don't want to get in the middle of this little arguement. I just want to share what I've seen with my own eyes.
If the upper 90's and 700+ hp on pump gas is a compromise, it's one I could easily live with.
I guess it all depends on what it is you're trying to do. Personally, I just run the lakes and rivers (no organized racing) and I'd like to spend less than $5 per gallon for fuel, have my boat start and run competitively every time I turn the key. I'd be cool with that.
Currently running 10.250:1 with Iron 990's... Use pump gas all the time for 3 years now and 98% of the time all the gas has been purchased at the river (in town) Never had a problem :rolleyes:
HBjet

[Wally_Gator]

Not to stir the pot....
Is it a valid statement that Alum heads are less prone to pre-ignitiion at higher
compression ratios than Iron heads due to aluminum's heat transfer properties?
Also.. Can the Pump Gas friendly boats we are referring to like HbJets running iron heads be attributed to the relatively cold water used for coolant?

[Squirtcha?]

Also.. Can the Pump Gas friendly boats we are referring to like HbJets running iron heads be attributed to the relatively cold water used for coolant?
I believe that's got a lot to do with these motors running the numbers they do, on pump gas......... (without splode-itating).

[flat broke]

Not to stir the pot....
Is it a valid statement that Alum heads are less prone to pre-ignitiion at higher
compression ratios than Iron heads due to aluminum's heat transfer properties?
Also.. Can the Pump Gas friendly boats we are referring to like HbJets running iron heads be attributed to the relatively cold water used for coolant?
Yes and Yes. I don't know what the operating temp is Randy's motor, but on mine (right at 11:1 on 91 octane) I don't like to see water temps higher than 120*f.
Chris

[flat broke]

I have spent alot of time pushing the envelope of pump gas engines. I know what detonation is and the things that cause it. I do this for a living. You can TALK about it all day long . I'll still be working on new combos, pushing the envelope,custom ordering cams that really dont change hp/trq enough to even bother ordering. Once you guys figure out that pump gas is a comprimise in its self, you might stop yacking about custom grinds/air flow bla bla bla. All of these little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor that puts out 1.3 hp/ci. So build your favorite pump gas motor and prove it to yourselves. Hey Hal, I like the AFRs and the previously mentioned cam.
A lot of people, do spend a lot of time TALKING about different combinations. The reason why, is because in the face of an honest exchange of factual information, a lot can be learned by sharing the resources of different people trying different things. You can sit in your shop and put combo after combo together in a trial and error fashion, or you can get out and talk to people who know what's what, and have some data to pour over. You get the benefit of the money they spent on trying something, without having to spend it yourself.
As for your statement about pump gas motors, 1.3hp/ci hp levels, and cam and head variances. If you think that you won't get the bang for your buck out of a $600 custom ground cam all by itself, you are right. But if you open the scope of your vision up to encompass the entire engine and the synergistic effects of complementing hp gains from one part to another, you might see that you are wrong with your statement that the tricks that work on 1.95 hp/ci motors dont carry over to pump gas deals. There are more than a few NA motors in boats on this board putting out in excess of 1.6 hp/ci on 91 octane.
Altered firing orders, custom lobe profiles, shear plates, etc. are employed on most of these motors. I think these items would fall into the, "little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci" category by your definition. But there is no denying that when you start to apply the theories behind the parts, substantial gains can be made looking at the engine as a whole.
As far as proving it to myself, I already have. My setup is a 498 making 821hp at 6200. I'll be very upfront and say that I had my motor professinally built. But, I can comfortably say that I fully understand principles at work that allow my motor to make more HP than most others of similar ci/build/fuel requirements. Steelcomp actually did his himself, and I believe got very similar results with a little insight from the same builder I used.
To each their own on how they do things. Thats what makes everyone unique, and the world a fun place to live. But just because you didn't have luck with a certain combination, doesn't mean that it is a bad combo, or less favorable than what worked for you. There is a difference between saying, "little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor", and saying something along the lines, of " all the little trick things that net 10-15hp on a 1.95 hp/ci mill, didn't seem to work for the pump gas engine that I built. That's the gist of the point I'm trying to make.
Chris

[steelcomp]

What is Pre-Ignition? What is a Fuel Kernel ? What is BMEP ? Go read a book, You will get the answers
I know very well the answer to my question...I was just trying to find out if you really understand what's going on in a combustion chamber, since you've "pushed the limits" as you say. By your response, I'm guessing not.
You should really tone down the arrogance behind your comments. You've made comments and suggestions here on these boards that sound extremely amaturish, and don't seem to reflect your claims of expertise. When you can trade ideas and hold a meaningful conversation with someone like Larry Widmer, Darin Morgan, French Grimes, Steve Schmidt, and the likes, then you might be able to justify your seemingly superior tone. These guys "do this for a living", and don't spend a lot of time talking about it. I'm sure you've worked very hard at what you've accomplished, and that's good. To come on here and talk down to people the way you have, is not.

[77charger]

Yes and Yes. I don't know what the operating temp is Randy's motor, but on mine (right at 11:1 on 91 octane) I don't like to see water temps higher than 120*f.
Chris
so at over 120 is it still a pump gas motor? :rollside: Or can you back timing down to be safe

[MikeF]

so at over 120 is it still a pump gas motor? :rollside: Or can you back timing down to be safe
Need some transducers for some realtime data on the combustion chamber/plug temps to see how far it can be pushed (under full load of course). :boxed:

[cyclone]

I have spent alot of time pushing the envelope of pump gas engines. I know what detonation is and the things that cause it. I do this for a living. You can TALK about it all day long . I'll still be working on new combos, pushing the envelope,custom ordering cams that really dont change hp/trq enough to even bother ordering. Once you guys figure out that pump gas is a comprimise in its self, you might stop yacking about custom grinds/air flow bla bla bla. All of these little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor that puts out 1.3 hp/ci. So build your favorite pump gas motor and prove it to yourselves. Hey Hal, I like the AFRs and the previously mentioned cam.
I really like the AFR's too but i disagree with your statement that all the little tricks that net 10-15hp won't do jack on a pump gas motor. It's those little tricks that enable builders to push a pump gas boat motor to 900 and 1000- plus hp. Once you start taking advantage several of those little tricks it will mean the difference between an average pump gas burning motor and a truly incredible one. Sure if you only apply one or two of these tricks it won't mean much in the grand scheme of things, but apply several of them and the results will surprise you. There are plenty of builders who have proved this and built their reputation on assembling pump gas burning engines that outperform even some race-fuel burning engines.

[Dimarco Kid]

Cyclone....you run AFR's on yours? I got the ***boat article when the 572 was built right next to the bowl. I read it once a day!!!!LOL That motor ran AFR's too. Then I read that it ran 110 in a Rogers. Jesus, that's better than sex. So....point is....I got a new Dart Big M and going big, might even copy that build up. But never have used anything but Brodix's (in drag cars), so just wondering!!!

[MACHINEHEAD]

Maybe if it were my own personal engine I would be able to spend the extra time. And there is a lot of extra time. These are engines that I build for customers. They need to be perfect for them. After I spend all of my personal time on my own engine I will be able to see the compounded effects of the little tricks. Not that my customers are not worthy of this extra time, they just dont want to pay for it. I just happen to be a little bias when it comes to Time/HP/Profit equation. The AFRs are a quick way to get to customer goals. Canfields are my plan B if money is an issue. I try not to sit around and stare and yap about a particular engine Im building for 8 mos. I would like to, so I can get everybodys opinion on it, but the boss starts getting REALLY pissed. No what Im sayin

[cyclone]

Cyclone....you run AFR's on yours? I got the ***boat article when the 572 was built right next to the bowl. I read it once a day!!!!LOL That motor ran AFR's too. Then I read that it ran 110 in a Rogers. Jesus, that's better than sex. So....point is....I got a new Dart Big M and going big, might even copy that build up. But never have used anything but Brodix's (in drag cars), so just wondering!!!
I did run AFR's on the the 572 and it was an good combo of off the shelf parts, like what Machinehead is describing. Easy to build, parts are easy to obtain, and it ran amazing for what it was. The Rogers ran a best of 9.13/116 mph with that motor with minimal set up and tune up work on the boat and motor. There was probably more left but the boat was a bit squirrely at that speed whenever the wind came up.

[cyclone]

Maybe if it were my own personal engine I would be able to spend the extra time. And there is a lot of extra time. These are engines that I build for customers. They need to be perfect for them. After I spend all of my personal time on my own engine I will be able to see the compounded effects of the little tricks. Not that my customers are not worthy of this extra time, they just dont want to pay for it. I just happen to be a little bias when it comes to Time/HP/Profit equation. The AFRs are a quick way to get to customer goals. Canfields are my plan B if money is an issue. I try not to sit around and stare and yap about a particular engine Im building for 8 mos. I would like to, so I can get everybodys opinion on it, but the boss starts getting REALLY pissed. No what Im sayin
That is true. I didn't factor in the time it takes to make those little tricks work and you are right, it is significant. If my job was building motors then that would definately have to factor into the buildup and price.

[Dimarco Kid]

You running a different engine in the Shadow? Must be alot nicer ride.

[cyclone]

i ran that same 572 in the shadow last summer. building a new engine now though.

[Dimarco Kid]

i ran that same 572 in the shadow last summer. building a new engine now though.
Mind if I ask what the performance difference was between the two hulls?

[cyclone]

The Shadow is 10mph and about 3/10 quicker so far versus the Rogers. But i'm running a different pump with the Shadow so i wouldn't make it an appples to apples comparison.

[holorinhal]

I am narrowing My choice of heads.
The AFR 305's look real good. but they are rectangle port heads.
I was under the impression that the oval port heads ,were the best port choice for jet boat applications.I am also looking at the brodix bb-2 and bb-2 plus,which are also rectangle port.
will a rectangle port head work as well in a jet.What might be the pro's and cons to using a rectangle port head?

[MAXIMUS]

I would strongley suggest looking into a set of "Pro Topline" as cast 320cc. They are priced really good. I have a set on my injected 496 & a buddy of mine is running a set on a 468 tunnel ram deal. Both set ups are out of the box with no porting. They flow very well for what you are looking for! I am also running a set of dart 360 & AFR 315 cnc's. The pro toplines are really nice... :)
Check out the link
http://www.protopline.com/racingaluminumbbc.htm

[flat broke]

I am narrowing My choice of heads.
The AFR 305's look real good. but they are rectangle port heads.
I was under the impression that the oval port heads ,were the best port choice for jet boat applications.I am also looking at the brodix bb-2 and bb-2 plus,which are also rectangle port.
will a rectangle port head work as well in a jet.What might be the pro's and cons to using a rectangle port head?
The problem with "rectangle" port heads as you know them refers largely to the GM rectangle port castings. These heads have large runners and don't have good airflow velocities at lower RPMs. That is why they don't work well for most jet boat motors. Now the aftermarket heads your are looking into will flow more at lower lift numbers than the Chevy rectangle port heads, and will do so with greater velocity at lower RPM. There have been lots of recommendations floating around, and unless you're going to spend a full day on the dyno with the motor tweaking for the ultimate tune, you'd be in good shape with a lot of em. AFRs are nice, but pricey and sometimes you have to wait. I've heard good things about the Pro Toplines, but have also seen that they are not cast or finished as nice as a set of AFRs or Canfields. Then there is my preference the Canfield. I have already posted my thoughts on these heads, but to recap, my motor pulls 821hp out of em on pump gas with a tunnel ram and 2 850s. They probably have the best exhaust port on the market in the class of heads you are looking at, and dollar for hp potential they are a better buy than the AFRs IMHO.
Good luck with it.

[holorinhal]

Chris
I was in fact looking at the Canfields,last night and the 310's look real good and are priced real nice too,but they are also rec port and I was just unsure of the rec port heads on a jet application.But if I under stand right ,the aftermarket "rectangle heads are fine in jets.
Is it better to have a smaller runner volume or larger runner,when considering heads for high hp motors?

[steelcomp]

Forget about the shape of the port...it's irrelevant.
AFA port volume, smaller is always better, but again, don't get hung up on names and terms. There's a correct runner volume/flow for each engine application and it's not something you can generalize about. Chris
I was in fact looking at the Canfields,last night and the 310's look real good and are priced real nice too,but they are also rec port and I was just unsure of the rec port heads on a jet application.But if I under stand right ,the aftermarket "rectangle heads are fine in jets.
Is it better to have a smaller runner volume or larger runner,when considering heads for high hp motors?

[flat broke]

Steelcomp's recommendation is as accurate as it gets and he knows a hell of a lot more than me. To somewhat answer your question more directly, yeah a 305-310 cc deal should be a better match to your CI range, pump gas friendly compression ratio, and intended RPM range use than something larger like a 355 etc.
PM Cstraub here on the boards once you make a decision on your heads and he can get you going with a good cam profile that will work well within the range of your applicaiton.
If you haven't purchased your pistons yet, make sure you can get something that will net you a desired CR with the combustion chamber volumes you are looking at in the various heads you're considering. If you have purchased your pistons, then it is even more critical that you know how far down they sit in the hole, and how much volume they consume at TDC in the combustion chamber so that you can accurately deterimine your static CR. Great heads will only go so far if the rest of the combination isn't optimized for the best results.
Chris
Chris
I was in fact looking at the Canfields,last night and the 310's look real good and are priced real nice too,but they are also rec port and I was just unsure of the rec port heads on a jet application.But if I under stand right ,the aftermarket "rectangle heads are fine in jets.
Is it better to have a smaller runner volume or larger runner,when considering heads for high hp motors?

[holorinhal]

Pistons have allready been purchaced,they are JE/SRP dome tops.
Why the canfield 310's and not the 350's? those are the only two heads ,that I see,they offer for the BBC.
Do any Of You know of any web sites or books,that explain the principles and workings of heads and cams,that will help Me better understand all aspects of how they work? Thanks ..Hal

[flat broke]

You would want to look at SRP's website for the pistons you have assuming a 0 deck height and use the volume of their dome profile compared to the different combustion chambers available for each head to determine your CR. Canfield can do your chambers in 113/119/125cc CNC profiled versions for around $100 more per pair. This would let fine tune your CR beyond what a "one size" combustion chamber would allow. I believe the 119cc chambers are standard on the Canfields.
Now as far as your question about the 350s vs the 310s. If you get the 350s they are going to be a little lazy on a 489. What's worse is that if you have any "work" done to the runners, the airflow potential may improve, but the velocity will probably drop. The 310 will get outflowed by an AFR 335, but not by much and according to AFR's own printed data...
Cylinder Heads used for testing are as follows:
#1 Canfield 305 #9 Dart Pro 1 (325 cc)
#2 World Products Merlin VR (Cast Iron) #10 Edelbrock Performer RPM
#3 World Products Merlin (Aluminum) #11 Brodix -2X
#4 Holley Avenger #12 Brodix -4
#5 GM 188 (Cast Iron) #13 Dart Pro 1 (345 cc)
#6 GM 990 (Cast Iron) #14 Brodix -3
#7 Brodix -2Plus #15 Edelbrock Victor 7760
#8 GM Performance Parts 401 #16 Edelbrock Victor (CNC Port)
Cyl. Head AFR 315 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
CC's 315 305 310 310 314 317 318 318 322 325 325 345 345 345 370 370 375
0.100 76 75 79 73 72 68 69 72 70 76 73 72 76 79 80 71 78
0.200 162 161 158 144 137 129 125 150 143 141 146 134 149 141 139 145 146
0.300 232 215 216 217 199 188 183 207 200 200 204 185 210 199 195 207 211
0.400 282 257 258 269 251 233 233 252 236 251 248 232 260 254 245 254 264
0.500 321 303 292 289 292 259 264 287 275 293 282 277 299 292 293 290 307
0.600 348 328 313 296 315 291 292 318 310 325 300 314 328 323 333 322 338
0.700 368 339 325 305 330 313 - 337 330 345 318 340 351 350 360 342 354
0.800 370 332 327 312 340 - - 336 340 355 319 360 352 365 366 356
Avg. Flow 298 276 270 262 266 247 240 270 262 273 260 263 278 275 276 272 293
Cyl. Head AFR 315 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
CC's 315 305 310 310 314 317 318 318 322 325 325 345 345 345 370 370 375
0.100 62 61 57 66 60 45 53 55 53 58 58 57 66 59 56 57 58
0.200 133 115 100 129 122 90 103 111 116 95 116 93 127 108 83 115 122
0.300 199 163 141 173 171 131 140 139 142 140 144 133 163 142 118 143 190
0.400 256 199 175 195 207 170 176 174 179 180 175 165 192 183 150 180 230
0.500 284 228 193 207 233 188 198 201 204 215 203 193 222 216 188 208 266
0.600 290 251 207 214 252 195 204 225 227 238 226 222 244 241 216 230 282
0.700 293 265 213 214 264 200 207 240 244 255 244 240 256 256 230 246 287
0.800 300 273 222 214 269 202 207 252 259 273 259 252 263 273 245 259 287
Avg. Flow 251 213 179 192 217 168 176 192 195 199 195 185 210 203 176 197 238
Avg. I/E Ratio 84% 77% 66% 73% 82% 68% 73% 71% 74% 73% 75% 70% 76% 74% 64% 72% 81%
NOTE:
AFR 315 exhaust flow figures were obtained using the optional tulip valve that comes standard on the AFR 335 and 357 cc packages. The standard valve that comes with the 315cc package would flow approximately 10 CFM less (Refer to our website or 2002 catalogue for exact flow figures.) AFR feels 84% is actually too high an intake/exhaust ratio for a normally aspirated engine and utilized the different exhaust valve to bring the ratio down to 81%.
IMPORTANT:
Many of the competitor's heads advertised in this testing have MUCH LARGER intake runner volumes. Keep that in mind when evaluating the flow figures advertised. AFR also offers larger intake runner volumes that will be tested shortly. (Refer to our website or our 2002 catalogue for accurate flow figures on the entire Big Block product line we offer.)
VERY IMPORTANT:
All flow figures taken in this test were recorded using a 4.250 bore fixture. Current chamber designs and valve sizes used today (typically 2.250 - 2.350 for BBC intake valves) would show better results being tested on the larger 4.500 bore fixture. (Primarily due to unshrouding the valve with the larger bore size.) With so many production GM blocks, as well as the aftermarket, starting at 4.500 inches in bore size, we feel this is much more representative of the current trend in Big Block Chevy engine building. All published flow figures from AFR were obtained using a 4.500 bore fixture. However, the fact that all the information obtained at Westech was recorded using the same bore size (4.250), the same flowbench, the same operator, etc., this still proves to be a valid test and comparison, eliminating many variables that could potentially exist evaluating and comparing flow data.
Their 315 head barely outflows the Canfield 310.
All Canfield aluminum Cylinder Heads are cast from the finest A356 virgin billet, and are heat treated to a T6 condition. Canfield Heads are machined on the latest precision, computer controlled machining centers. As cast 119 c.c. chambers standard. Optional 113/119/125 CNC Profiled Chambers Available!
VALVE LIFT .100 .200 .300 .400 .500 .600 .700 .800
Intake Port 72 138 204 266 318 347 353 355
Exhaust Port 74 123 176 205 237 260 273 284
These are typical flow numbers at 28 inches of water measured on a SF 600 bench by an independent shop.
Now these numbers don't mean a whole lot as everyone fluffs their own crap, but they give you an idea. Pretty comparable performance potential, and one costs substantially less than the other.
If you have to compromise on runner size, I.E. choose between a 310 and a 350, on your size motor, going into a jetboat, I'd go for the 310. Asside from providing better response and probably a better torque curve, the head has the meat available to have an aftermaket CNC profile job done to take the runners to something in between the 310 and 350. If you were interested in doing something like that, call Canefield directly and tell them what you are looking to do with the motor.
Hope that helps,
Chris
Pistons have allready been purchaced,they are JE/SRP dome tops.
Why the canfield 310's and not the 350's? those are the only two heads ,that I see,they offer for the BBC.
Do any Of You know of any web sites or books,that explain the principles and workings of heads and cams,that will help Me better understand all aspects of how they work? Thanks ..Hal

[steelcomp]

Pistons have allready been purchaced,they are JE/SRP dome tops.
Why the canfield 310's and not the 350's? those are the only two heads ,that I see,they offer for the BBC.
Do any Of You know of any web sites or books,that explain the principles and workings of heads and cams,that will help Me better understand all aspects of how they work? Thanks ..Hal
Hal, maybe I can shed a little light here for you.
It all starts at the carb, on a carb'd naturally aspirated engine. The only thing that makes a carb work is the air flowing through it. The faster the air is flowing through the carb, the better it works, because the air "signal" is stronger. If a carb is too big, or the air is moving too slowly, the signal is weak, and the fuel metering isn't efficient. This leads to poor throttle response and a lack of power and performance, untill the air speeds up ( with the increase in RPM) and the signal improves. This is one reason why air velocity is important. The other reason has to do with cylinder filling. Again, low velocity will hurt good cylinder filling, won't promote the swirl, and won't help keep the fuel suspended in the air. When you get air/fuel seperation, again, you have poor performance due to bad combustion.
How the port plays in this is that when you have a given volume of air flowing through a given opening, or area, it's going to do so at a given velocity, or speed. To get that same volume of air to flow through a smaller opening, the velocity will have to increase. You can compare it to this. Take a toilet paper tube, and with as deep a breath as you can take, blow through it, aiming it at something that'll move, like some sand. Now do the same thing through a straw. The air coming out of the straw is moving MUCH faster than the air coming out of the paper tube. That's velocity. As the piston drops in the cylinder, it allows atmospheric pressure to fill the cylinder through the carb anad intake manifold and port. Ths smaller the port, the higher the velocity. Of course there are many many more variables than this, and this is an extreme oversimplification. The key is to know how much air your engine is going to require at whatever given rpm you intend to use it, and compare that number with the flow values of a given cyl. head. If your engine dosen't require 400cfm, there's no need for a head that flows that. If you have two heads that have the same flow numbers, and one has a smaller port than the other, there's there's the "paper tube vs./ straw" analogy, and you'd choose the smaller of the two heads. Again, this is an oversimplification, but maybe this will help you understand the difference, and the need for different size ports and flow values. In heads and cams, bigger is definately not always better.

[MACHINEHEAD]

AFR now has 265 and 290 ovals that look very impressive! Dont know anyone that has tried them though. 330 cfm@.600 btw. Seems a little high. Maybe these would be a good choice for hals pump gas ski/pleasure deal.

[steelcomp]

AFR now has 265 and 290 ovals that look very impressive! Dont know anyone that has tried them though. 330 cfm@.600 btw. Seems a little high. Maybe these would be a good choice for hals pump gas ski/pleasure deal.
Hal's combination, at a max rpm of 5700, and a lobe with 245@ .05 would require an intake flow of just under 300cfm.

[FILUCKY]

Hey Steel, i know this is kinda your specialty so correct me if i'm wrong but sounds like the AFR oval port heads would make a good choice here considering the intake CFM is close to the targeted area (300) but should have a smaller crose section then the rectangle? More volicity at lower RPM's (5-6000 rpm) and isn't the advitised flow numbers usualy a little higher then real world? Just my .02 :rollside:

[steelcomp]

Hey Steel, i know this is kinda your specialty so correct me if i'm wrong but sounds like the AFR oval port heads would make a good choice here considering the intake CFM is close to the targeted area (300) but should have a smaller crose section then the rectangle? More volicity at lower RPM's (5-6000 rpm) and isn't the advitised flow numbers usualy a little higher then real world? Just my .02 :rollside:Advertized flow numbers are usually a little more optomistic than real world, since manufacturers know that numbers sell. I know that, for instance, AFR has flowed their heads on a 4.600 bore fixture. Not very "real world" since there's a whole lot more 4.25+ bore big blocks out there than anything with a 4.600 bore.
The AFR ovals might be a good choice, but I'd check their flow numbers on the same size bore I was using to make sure. It also depends on other things like what the actual cam choice will be, what the actual max rpm will be, etc. I just posted the above numbers as a baseline for reference. You also don't want to max out the flow capacity of a head, requiring excessive lift numbers. Your comments about the smaller port having more velocity is correct, although not directly related to cross section, rather related more to port volume. Two different things. Cross sectional velocities are different than port velocities, and translate into different meanings AFA port and engine performance.

[Cs19]

Im still getting a kick out of this statement.. :)
All of these little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor that puts out 1.3 hp/ci.

[steelcomp]

Im still getting a kick out of this statement.. :)
Originally Posted by MACHINEHEAD
All of these little trick things that net you 10-15 hp on an engine that makes 1.95 hp/ci, doesnt do jack on a pump gas motor that puts out 1.3 hp/ci.
LOL. Maybe that's why his pump gas motors only make 1.3 hp/ci. :cry: :D

[Cs19]

Man,Im really kicking myself now. I didnt realize a 91 octane engine wouldnt respond to the little tricks.. :rollside: What a waste. :)

[holorinhal]

AFR now has 265 and 290 ovals that look very impressive! Dont know anyone that has tried them though. 330 cfm@.600 btw. Seems a little high. Maybe these would be a good choice for hals pump gas ski/pleasure deal.Guy's,Please let Me clarify somthing here.I thought that I had said this in a much earlier post,but maybe I did fail to mention.
My focus on what type of boat I am building here,has changed.I am no longer considering this motor for skiing or towing of things.Icant say it is'nt for pleasure becouse I intend to get a great deal of enjoyment out of it,but it won't be for lazilly cruizing.I am build ing another boat for that purpose!
What I am building here is a motor that will be competitive with most of the boats on the river that like to dable in the occational friendly drag/bracket race.
I would like to be able to get as much hp from my motor with the 10.5-1cr,as I can ,but without having a cam profile so large, that the motor will be wanting to kill at idle.thanks....Hal

[holorinhal]

I do appreciate all of the very informative info from all of You Guy's.I have and still am learning so much in these threads,so please keep it comming.
I have rebuilt several smalblock's and one bb,but only as stockers,with the bolt on goodies,But have not built any thing that was relly considered a High performance or race engine.Once again,thank You for taking the time to educate Me..........Hal

[MACHINEHEAD]

Hal is saying that he wants to get as much HP out of 10.5 to 1 as he can, BUT. Isnt he having this engine built by someone. Maybe the little tricks are not in the budget. Maybe ,But, But , Maybe! My possision on the little tricks is a few posts back. Take it easy everyone summer is near :boxed:

[flat broke]

holorinhal,
I think what most of us mean by a "non race" engine is that the thing will not be spining 6200-7500RPM. More than likely you'll end up spinning 5500 or thereabouts with a properly loaded and sized impeller. Regardless of how "Bad ass" you want the motor to be, if you build it to be a "race" motor and the guy that you are using doesn't understand that it needs to be at peak HP by no later than 6k or so to work efficiently in your jetboat; you'll have a dog on your hands, regardless of the flow numbers for whatever heads you choose.
Since it looks like you have a static CR picked out that you would like to use, perhaps you should start looking at your head choices based upon your already purchased pistons, and the combustion chamber volumes that are available over the counter. Sure you can whittle away on pistons, or deck brand new heads, but since you're building from scratch anyhow, try and get as close to your desired CR as possible with the combustion chamber of the head you choose.
And again, just because a set of 350cc runner Brodix, Canefield, AFR, whoever's heads show awesome flow numbers; doesn't mean they are going to perform well on your relatively small CI (by todays standards) motor. Those of us running displacements similar to yours have posted up our info and suggestions. Not to sound arrogant, but Steelcomp, CS19, and myself all have dyno proven combinations that utilize the advice we're giving you. IMHO, the proof is in the puddin' when you hit the water, but I attached a shot of one of the dyno pulls on my mill, mainly to illustrate that you can definitely have what many folks would consider a "race" engine that doesn't use large runner heads.
http://www.***boat.com/image_center/data/500/280498peak.jpg That motor is two years old, so I'm sure there have been improvements in the HP department out of that shop at similar displacements. But for reference, those numbers came using a set of small Canfields with a CNC profile job done on them, and runs on nuthin but 91 octane.
Good luck with your build,
Chris

[MACHINEHEAD]

Sweet numbers, nice TQ even to 6k. Something like that will take care of a few hot heads on the river, aye HAL!

[holorinhal]

Machinehead,
I am having the motor built by a builder.However the reason for Me engaging in these treads,is for My own education and not so I can tell My builder how to build an engine.
If I were to just hand Him a wad of cash and tell him to build Me a motor ,He would probobly build the thing,build it right and then when all is said and done,I would have a motor that I knew nothing about.
I just want to have an opinion as to how and what I want with the guidance of someone who is more experianced than I am.
I want to learn what all the "little trick's"are ,that will give Me a little more out of My combo.
If I had known more,I might have decided to purchase Pistons that would give me a higher copression ratio.Unfortunatly I made the decition based on wanting a "ski/pleasure" deal,but now I have got the performance/go fast bug,which has changed the focus of My build.
At the start,aftermarket heads wer'nt in my budget,but I am taking the plunge and stepping up to the plate,so I would'nt say that all the little tricks are not in My budget,it's just I don't know all the trick's.My builder might know ,but I do'nt,and I would like to.Just like the fact that I thought the oval ports were the only head good for a boat.Now I have learned that rectangle ports on the aftermarkets are much better than the old factory rectangle iorn chevy head's.
At any rate My pistons have been purchased ,It is what it is! It's a 10.5-1 cr motor.You may call it low compretion,But it is higher than a standard cr motor and I can live with that! My objective now is to learn what I can do to get the most out of what I have to work with. I know there are some motors out there that have muscle and run strong,with less compretion than I have.
Would a head with a Smaller combustion chamber,be wise to raise the cr a little?...Hal

[steelcomp]

Hal, here again, don't let some of these guys get you stuck on numbers. It's all they really know, and means nothing. A compression ratio isn't any thing more than a reference, and really has little to do with what kind of gas you burn, and how much power you make. I know of turbo'd motors that put out over 2hp/ci, that run over 12:1 static cr, and run pump gas. There are 11:1 Big Blocks here on the boards that run pump gas, and make over 800 hp. The key is building dynamic cylinder pressure, and controlling what goes on in the combustion chamber. Static compression ratio is what's so, but it's also so what. What's important is the relationship bewtween the top of the piston, and the combustion chamber, and what happens to the gas when it's compressed, not necessarily how much it's compressed. Some piston/chamber combinations do a poor job of compressing the gasoline causing molecules to seperate, and detonation occurs. They can only get away with compressing so much at one time. Other more specifically designed chamber/piston combinations allow for much higher static compression ratios since they control the "squeez" much beter, keep the fuel suspended, and all but eliminate detonation. It's one of the reasons I like the Canfield heads...I really like their combustion chamber design, and flow numbers aside, I think that's where some good power potential is with them.
For what it's worth, I know of an engine builder, probably one of the best in the world, who dosen't even check compression ratios when he builds a motor. He designs the piston and chamber to do what he wants them to do. The "ratio" is unimportant. Unfortunately, we don't have that freedom with what we have to work with, but you get my drift.
Don't worry about your compression. Raising your compression just to have higher compression is a waste of time. Learn why gasoline detonates, and what life is like in the combustion chamber. Learn about things like "quench" and "swirl" and find out why one chamber is better than another. Look into how piston dome shapes can effect combustion, and what a "compression ratio" really is, besides just a number. Then, maybe you could teach your engine builder a thing or two. :D

[flat broke]

Steel,
I agree 100% with what you are saying in regard to the static CR not being an absolute more is better situation type situation. But would you agree that if the builder knows what he's doing with regard to whats going on inside the combustion chamber, and can get a higher static CR that still gives the same combustion control characteristics associated with a lower CR in a good burning head; the higher static CR should equate to a higher dynamic CR?
Sorry for the run on sentence :D
Chris
Hal, here again, don't let some of these guys get you stuck on numbers. It's all they really know, and means nothing. A compression ratio isn't any thing more than a reference, and really has little to do with what kind of gas you burn, and how much power you make. I know of turbo'd motors that put out over 2hp/ci, that run over 12:1 static cr, and run pump gas. There are 11:1 Big Blocks here on the boards that run pump gas, and make over 800 hp. The key is building dynamic cylinder pressure, and controlling what goes on in the combustion chamber. Static compression ratio is what's so, but it's also so what. What's important is the relationship bewtween the top of the piston, and the combustion chamber, and what happens to the gas when it's compressed, not necessarily how much it's compressed. Some piston/chamber combinations do a poor job of compressing the gasoline causing molecules to seperate, and detonation occurs. They can only get away with compressing so much at one time. Other more specifically designed chamber/piston combinations allow for much higher static compression ratios since they control the "squeez" much beter, keep the fuel suspended, and all but eliminate detonation. It's one of the reasons I like the Canfield heads...I really like their combustion chamber design, and flow numbers aside, I think that's where some good power potential is with them.
For what it's worth, I know of an engine builder, probably one of the best in the world, who dosen't even check compression ratios when he builds a motor. He designs the piston and chamber to do what he wants them to do. The "ratio" is unimportant. Unfortunately, we don't have that freedom with what we have to work with, but you get my drift.
Don't worry about your compression. Raising your compression just to have higher compression is a waste of time. Learn why gasoline detonates, and what life is like in the combustion chamber. Learn about things like "quench" and "swirl" and find out why one chamber is better than another. Look into how piston dome shapes can effect combustion, and what a "compression ratio" really is, besides just a number. Then, maybe you could teach your engine builder a thing or two. :D

[steelcomp]

Steel,
I agree 100% with what you are saying in regard to the static CR not being an absolute more is better situation type situation. But would you agree that if the builder knows what he's doing with regard to whats going on inside the combustion chamber, and can get a higher static CR that still gives the same combustion control characteristics associated with a lower CR in a good burning head; the higher static CR should equate to a higher dynamic CR?
Sorry for the run on sentence :D
Chris
Chris, I think in any given case, more static cr will give you more power, given that you can take advantage of it with either better gas (needed with less than optimum chamber/piston designs) or a chamber and piston combination that's going to minimize detonation. Simply stated, by compressing the fuel mixture more, it's going to burn better, which will result in higher dynamic cyl. pressure, which is where the added power comes from, so the answer to your question is yes, I agree fundamentally, but there are a lot of variables playing here, the biggest being cam timing. Low compression engines can be "fooled" into thinking they have more compression by designing the cam to increase dynamic cyl. pressure, allowing pump gas to still be used, and not suffer from increasing the mechanical (static) pressures that would otherwise cause detonation. That was the point I was trying to make for Hal.

[LVjetboy]

Drat my low compression 87 octane burning hog of an engine. Guess I'll just ski and tow with it :)

[MACHINEHEAD]

Check out the new popular hotrodding with the 65 goat on the cover. Theres a look inside a dudes motor that I think won the engine builders challenge. Nice deal 851hp on pump gas. Crazy!

[steelcomp]

Check out the new popular hotrodding with the 65 goat on the cover. Theres a look inside a dudes motor that I think won the engine builders challenge. Nice deal 851hp on pump gas. Crazy!I read that...now THAT guy made sure that all the hairs on the gnat's ass were all the same length! :D Good example of all the "little details" adding up on a pump gas motor. Tweaking the H bars on the lifters for less friction? I think it said 12 lbs/ft to rotate the completed short block? Whew! And I thought I was anal! :rolleyes: