Cylinder head recommend.

[freakdave]

I'm procuring parts for my first engine build, 509cid n/a. So far i got a dart big m, forged crank,rods,pistons, crane "741" cam. My pistons are flattop with -2.5cc relief. Will prob go with air gap intake and demon 850. RPM max around 5500rpm, not going to be used for racing. Would like to get 575-600hp with a nice broad torque curve. I want 9.5+ CR which means i will have to use 110cc heads. Question...Rect or Oval port? I'm looking at the Edelbrock oval port with 110cc. Are these considered a "large" oval? I plan on cleaning up the heads with some mild port/polish work. There really seems to be alot of debate over oval v. rect. When using .600+ lift cam like the one i have does that have a lot to do with it? thanks, dave

[BrendellaJet]

what drive are you using?

[freakdave]

havent decided on the actual boat yet, more than likely a cat or sport deck. the drive would prob be a xr or modified bravo1.

[cfm]

HP 500 refresh :
AFR 305's with cnc chambers
Kept Dart Intake (HP 500)
Kept 800 Holley (HP 500)
custom HR cam (smaller than 741)
620hp
Picked up around 10mph on 38ft'r with twins vs stock HP500's.
Oh, still has HP500 Gill exhaust manifolds too.
Impressive package.

[steelcomp]

Wondering how it is that you already have a cam picked out but don't even have heads yet?I'm procuring parts for my first engine build, 509cid n/a. So far i got a dart big m, forged crank,rods,pistons, crane "741" cam. My pistons are flattop with -2.5cc relief. Will prob go with air gap intake and demon 850. RPM max around 5500rpm, not going to be used for racing. Would like to get 575-600hp with a nice broad torque curve. I want 9.5+ CR which means i will have to use 110cc heads. Question...Rect or Oval port? I'm looking at the Edelbrock oval port with 110cc. Are these considered a "large" oval? I plan on cleaning up the heads with some mild port/polish work. There really seems to be alot of debate over oval v. rect. When using .600+ lift cam like the one i have does that have a lot to do with it? thanks, dave

[freakdave]

the cam was a freebie from a friend, brand new though. dont HAVE to use it but i got it and if i can save some$$ then even better. the cam is used in quite a few marine applications esp 500+ cid engines that turn up to 5500 rpm. are you going to answer the question about the cylinder head recommendation? will the large edelbrock oval ports with 110cc chambers with a little cleaning up do the trick ? especially for the money, they are less expensive than other brands and i am on a budget.

[poncho-pwr]

The Edelbrocks will certainly work for your application, but I would probably put a set of Canfield 310 heads on it. The AFRs are very nice too and would work well but that little Canfield 310 has really impressed me and I think it would be a better choice than the Edelbrocks and you should be able to get a good price on them complete. I also agree with steelcomp that it is a bit backwards that you have chosen your cam before choosing cylinder heads yet. The cam and heads package is where the power is at. That cam may be used in a lot of marine applications like yours and it may very well work okay in your deal, but if you want to get the most out of your combo and not be kicking yourself down the road, you need to select some heads, have them cleaned up a little for your application by someone who knows what they are doing and then have them flowed. After doing that give the engine build details as well as the flow numbers from the heads to a reputable cam designer and let them help you pick out the right cam for your application. You are not just trying to throw something together that is a cheap run whatever you can come up with for free combo or you would have not purchased a Dart Big M block. Spend the money wisely and get the right cam, you will thank yourself down the road. By the way, cstraub69 here on the boards is a very sharp cam designer and I would highly recommend you contacting him when it comes time to get a cam. HTH

[freakdave]

cool, thats what i'll do. i sent an email to AFR for their recommendation and i'll check with canfield as well. as far as my combo goes, 509 with flat-top pistons, i'm guessing a large oval port or smaller rect port design would be the way to go. seems to be lots of discussion between the two. i really want to get it right the first time. i'll check with straub.

[poncho-pwr]

Quit worrying so much about rectangle vs oval port. There is more to it than that. In the Canfield 310 you have a head that flows very well but has a smaller runner than most of the other heads that flow as good as it does, and that usually means that you can make more power throughout the rpm range. That is an over simplification but you get my point.

[steelcomp]

I can pretty much ditto what Poncho said above. You're not oging to get any better bang for your buck than the Canfields, although the chamber size may be an issue for you if you're going to run those pistons. I think you can get the Can's down to 113cc. Have them flowed, and ahve a cam spec'd for your particular app. The cam you have may work on a variety of engines, but I guarantee you'll be leaving HP on the table. The cam is just about the last thing to buy when building an engine, since it's design is basically dictated by everything else, as a combination. If you don't know the combination (bore, stroke, rod length, compression, intake, carburation, exhaust, flow numbers, and intended usage like prop, hull, and rpm range, etc.) you're really only guessing at a cam. You give Chris all this info, and I will guarantee that he will get the optimum out of what you have.
Rect port vs. oval port is way over analyzed in apps like this. You need to find out what kind of flow requirements your engine is going to need given the rpm range you're looking at, and then pick a head accordingly. No sense in getting a head that flows 400 cfm if all you need is 240. The 310 Can has great mid range flow specs, and as stated above, very good flow for a 310cc head...better than most 325's. It's getting most of it's flow between .300-.600 lift, which is good. The ex port is what I like most...very effecient, which allows the cam grinder to go easy on an ex lobe profile. The easier the profile is on the cam, the easier it is on parts. Pretty simple. The Can's are also very reasonably priced.
Talk to Chris Straub.
Good luck.

[cfm]

Freakdave - is your exhaust thru transom or over transom ? Is it an I/O Bravo drive by any chance ?
What kind of boat + application is this motor being installed in ?
Reason I'm interested in exhaust set up is because the Canfield's have a raide exhaust port (.625") that can cause some $$$$ reconfiguations if using a thru transom exhaust - depending on which type.
I've been involved in a few Canfield I/O builds, thus my heads up.
Steelcomp - yes, Canfield offers that smaller combustion chamber in a CNC version. However, it could take some major tooth pulling to get these in a hard anodized version within even a few month time period. You'd have to call and ask - and of course don't believe 100% what they say. LOL.
And yes - as mentioned that '741 might not be the answer. Everything needs to be looked at to choose the cam specs.

[cfm]

havent decided on the actual boat yet, more than likely a cat or sport deck. the drive would prob be a xr or modified bravo1.
Ooops, just saw this.
You have an I/O. Now, we really need to know what exhaust (wet/dry) you are going to use and which manufacturer's.
AFR, Dart uses approx .300" raised exhaust port and usually prevents little tailpipe fitment issues. Canfield's / BMF's / Jeg's with their .625" raised exxhaust ports can and usually do call for custom tails or etc.
Knowing now this is an I/O I would strongly suggest running a Dart or Vic Jr intake. I prefer the Darts in these apllications.
BG850 works terrific on these. Cstraub , I think, has some Holley 800's also.
Anyway - the trick with I/O's is to be able to run/prop boat at peak hp at WOT so your engine combo is very important in order to target this rpm. Reversion is a REAL issue that we must work with too. Cam, cid, cyl head, + exhaust has everything to do with this.

[MikeF]

Steelcomp - yes, Canfield offers that smaller combustion chamber in a CNC version. However, it could take some major tooth pulling to get these in a hard anodized version within even a few month time period. You'd have to call and ask - and of course don't believe 100% what they say. LOL.
I tried to do exactly that earlier this year. It was taking too long so I ended up cancelling the order. :frown:
Thought I would just put it back together for this season......then the inshore fishing got good and I got lazy about the boat. :mix:
Still going together, but slowly. :hammer2:

[freakdave]

i appreciate all the advice. does anyone have experience with AFRs BBC oval port heads. I sent them a email a while back with no response. I found a local machinist that has a dyno, hopefully he'll have a flow bench as well. Looking forward to this project. thanks, again

[cfm]

Last I heard the AFR oval ports still aren't out yet. They got totally fludded with orders for their latest Gen small block stuff this year which took the resources they need to get the BBC's rolling.
Anyway - they supposedly are hoping for this winter and many of us can't wait until they are available.
I personally believe their CNC Ovals with a Dart Oval single plane, 850 carb, 9:1 compression, and matched HR cam will make some serious steam on the 502's. I'm biting my nails in anticipation.

[freakdave]

hell yeah, if i get a set of those i'll let you know what happens. i'll probably go with a dual plane oval cause i'm looking for that midrange power, might add a 1-2" phenolic spacer for a little downward velocity if that helps at all. i'll probably dyno the motor once finished with and without a phenolic spacer to see if there is ANY difference at all. could be interesting.

[deltaAce]

I'm procuring parts for my first engine build, RPM max around 5500rpm. Question...Rect or Oval port?
I believe the Oval port heads are your best choice, given your selected max RPM. Your not going to be able to enjoy the benefits of the enormous rectangle ports flow capabilities designed for 7500+ RPM. And the lazy low RPM torque. The oval ports are best for throttle response in your intended RPM range.

[cfm]

I've been involved with and observed, and so has Cstraub, a whole bunch of 502-509cid build up for Merc I/O power. Max targeted rpm on builds where from anywhere between 5200rpm and 5800rpm. HP is from 540 (at 5200) to 620
Torque will range from 580ft/lbs to 610ft/lbs with 8.75:1 to 9:1 compression.
I personally did a large testing session on a 502 that was purposely built milder than most would do. Why ? To see what different parts would do on such a mild build. This would give me great info on what would work better on typical builds that where built to peak there hp a little further.
Anyway - I even tested a rect port Brodix/HV2001 intake that is 'larger' than many other single plane's out there. Guess what ? Engine made more average torque then even the dual planes. HR cam had less than 225 at .050 ". Compression was 8.8:1.
Put a killer / appropriate sized cyl head on an air hungry big 500cid engine (yes - they are big ! Just doesn't seem like it anymore. LOL) and the single plane intake becomes a necessity.
An RPM will still work well, don't get me wrong, but the single plane will hang right with it from low rpm, start to pass it in medium rpm ranges, and then 'see yah.'
A 9.5:1 509cid with modern/high cfm oval port (AFR, Brodix) and single plane Dart Oval Intake is going to have a ton of air velocity.
305-315 Canfields + AFR's have been used in a large amount oiver the last few years with very, very impressive results. In fact, well ported Chev 325cc cast iron heads have been turning in some killer #'s and on water performance.
Just don't miss the boat on the camshaft. This can really mess things up. More cam's have been installed that narrow the torque peak vs HP peak because of the tq peak being high and the rpm peak being limited by either driver not wanting to push higher or the valvetrain used (ahem - many HR set-ups) losing control at a certain rpm. 5900 rpm anyone ?

[Party Cat]

I'm procuring parts for my first engine build, 509cid n/a. So far i got a dart big m, forged crank,rods,pistons, crane "741" cam. My pistons are flattop with -2.5cc relief. Will prob go with air gap intake and demon 850. RPM max around 5500rpm, not going to be used for racing. Would like to get 575-600hp with a nice broad torque curve. I want 9.5+ CR which means i will have to use 110cc heads. Question...Rect or Oval port? I'm looking at the Edelbrock oval port with 110cc. Are these considered a "large" oval? I plan on cleaning up the heads with some mild port/polish work. There really seems to be alot of debate over oval v. rect. When using .600+ lift cam like the one i have does that have a lot to do with it? thanks, dave
Very similar to what I had put together 3 years ago...
509 Gen Vi block
Dart Pro 1 heads
Crane 741 cam
RPM Air Gap intake
Holly 830
Dana exhaust
MSD dist/ignition
Tom @ Pro Marine put it together and dynoed 628hp@5500rpm/652tq@4200rpm

[freakdave]

what was your compression ratio? did you have any work done to the heads?