which cam should I use

[dgie]

I just got my engine back from the machine shop last week and today I degreed the (2) cams that I have. One is brand new and has a gross lift of .518 and the other is the original cam that the engine rebuilder first put in the motor. That one has a gross lift of .3920 I am wondering which one I should use with this motor, both are in real good codition, no pits,scoring, etc. The pump is a jacuzzi 12wj pump, the boat is 18ft long and relatively light. The engine is a stock 455 olds .030, Torker intake and a 750 cfm holley carb, and OT basset headers. Any sugestions on which cam would be best with this setup.

[TIMINATOR]

What are the durations at .050 and the lobe separation angles,and intended use of the boat? Timminator

[PC Rat]

Are you sure about the .3920?
That number looks too small.
Brian

[dgie]

I do not have a cam card for this cam all the numbers below are from me sticking a degree wheel on it. The cam has a gross lift of .3936. (.246 x 1.6 = .3936)
The other numbers for this cam are as follows:
Intake
155 degrees + 66 degrees = 221 degrees / 2 = 110.5
Exhaust
157 degrees + 57 degrees = 214 degrees / 2 = 107
Intake 110.5
Exhaust 107.0
Total 217.5 / 2 = 109
[ September 14, 2003, 09:53 PM: Message edited by: dgie ]

[dgie]

sorry I originally said .3920 Gross lift its .3936 and the boat is intended for regular lake use.
[ September 14, 2003, 11:36 PM: Message edited by: dgie ]

[Duane HTP]

Use the larger cam. Make it at least sound like a jet boat.

[dgie]

any ideas?

[396_WAYS_TO_SPIT]

I went with a comp cams marine grind. 230@.50 int/ex,110 lobe, .490 lift. I love it. It sounds good and the midrange torque is outstanding. The rpm band is 2000-6000. My boat spins 4600rpm's. I have a 455 olds .30 over,tunnel w/ dual holley 600's,headers,and a jacuzzi wj with a diverter. to sum it up, i love it wink
396

[dgie]

hey 396 230@.050 is that the duration? excuse my retardedness I am new to this stuff. enough to get screwed into buying this huge ass cam from CP Performance and finding out now that it is too huge ass for my relatively stock motor. Venting, Venting......Now meditating......Ok I feel better now... So anyways is that the duration if it is how do you figure it out? The book that I have says open event + closing event + 180 I am lost here,,,How do I get the open and closing event. Also what is the grind number on your cam?

[svtrich]

why dont you try a Comp Cams 280.they are a good jet boat cam for an OLDS.
Richard :D

[THE BOSTON SIDEWINDER]

IS THE COMP CAM 280 GOOD FOR BIG BLOCK CHEVYS?...BILL.

[Jet City]

Dgie, first of all, you have not given enough info about your engine for anyone to make a sound recomendation. The Comp 280H is not a bad cam, but you need at least 9.5:1 compression ratio for it to work well, it would be an absulute pig in an 8.5:1 engine (Comp 268H would be far better here). So let us know what your CR is, this will drive what cam will be best for your application. Also, If I remember right, you can only run .500 lift on an Olds with stock rockers. Are you prepaired to also add adjustable roller rockers, and possibly valve spring seat work?

[dgie]

I did not include that information because unfortunately I do not know what it is. All I know is the engine is stock at .030. Torker Intake, 750 Holley....And I have upgraded the rockers to the crane cam ones with the elongated holes and stainless steel bridges. Rockers should be fine, I have already been thru this.

[dgie]

I am also going to play around with Desktop Dyno a little and see what it comes up with.

[flat broke]

dgie,
Perhaps you could run a compression test (forgive me if you already provided that info in another thread), and with that information one of the olds guys could give you an estimate on your CR. With respect to DTD, it's an airflow based iterator in which compression ratio will play a key factor in setting up your baseline information. This information needs to be in place before you start changing cam profiles to find something that works. The more known information you have, the more accurate the tool becomes. If you looked up the year of your motor, that might help lend additional insight into stock compression ratios and where you might be.
Good luck,
Chris

[dgie]

I have been hitting people up with questions on realoldspower.com and it turns out that one of my cams is way to big for my low compression motor and the other is way too small. Well I guess I going to have to drop a little bit more money on a new cam. the quote thay got me is like $50.00 from PAW, anyone heard of this place? I will get the number if yall want it. They seem to use this place a lot over there at that site.

[396_WAYS_TO_SPIT]

I went with the comp cam and matching springs. Look on thier online catalog. They only make 3 olds marine cams. These guys are right, you do need to know the compression ratio in order to get the right cam. Rule of thumb is to stay 230@.50 duration on a motor that is under 9.5-1 comp. the reason being that you will never spin the r's to make the horsepower. Plus you dont want that olds over 5k. Like I said my motor does great on the cam i used. My compression is around 9.5-1
396

[malcolm]

PAW's been around forever. Their catalog is like a full sized bible. :)
[ September 17, 2003, 08:09 PM: Message edited by: malcolm ]

[TIMINATOR]

Over 230 deg at .050 is fine for low(8.0 to 1)compression motors,the low compression only really affects the bottom end torque, somthing that jets don't need. A tight lobe separation angle works better in a low compression deal too. Comp Cams tight lobe center jetboat grinds work awesome! Have used a lot of them in stock 330 HP Big Block Chevys. Comp Cams will grind them on an Olds blaank for you,we order custom stuff from them all the time.Also for an Olds, find an old O4-B dual plane Edelbrock intake, works better than the Torker if you can find one.Also if anyone wants to debate compression V.S. duration at .050 step up and convince me that I'm wrong, I'll listen. TIMMINATOR argue

[Jet City]

TIMINATOR:
Over 230 deg at .050 is fine for low(8.0 to 1)compression motors,the low compression only really affects the bottom end torque, somthing that jets don't need. A tight lobe separation angle works better in a low compression deal too. Comp Cams tight lobe center jetboat grinds work awesome! Have used a lot of them in stock 330 HP Big Block Chevys. Comp Cams will grind them on an Olds blaank for you,we order custom stuff from them all the time.Also for an Olds, find an old O4-B dual plane Edelbrock intake, works better than the Torker if you can find one.Also if anyone wants to debate compression V.S. duration at .050 step up and convince me that I'm wrong, I'll listen. TIMMINATOR argue I have run both the Comp 268H and the 280H in my 8.0:1 CR 460 jetboat, the 268H resulted in 400 more rpm's and nearly 5 mph (GPS), it starts better and revs out quicker, the 280H was very lazy. No other changes on the engine took place (other than carb jetting of coarse). basically, the 268H builds more cylinder pressure in a low CR engine. I have also read that if you don't have sufficient static compression for a large cam, you will not effectively burn the A/F mix (due to the low-mid rpm compression bleed off of a larger cam in an engine that cannot afford the loss) causing the raw fuel to glaze the cylinder walls, my 8.0:1 engine has 145-150 PSI compression and 180+ PSI is needed for a 230 @ .050 cam to run at optimum, jetboat or not.
Dgie, I'd follow flat Brokes lead and do a compression test, that would give the needed data to choose a proper cam. If you know what pistons, deck height, head gasket and head castings where used you could also use a CR calculator to figure it out.
[ September 18, 2003, 07:30 AM: Message edited by: Jet City Rebel ]

[TIMINATOR]

78 SLEEK... The biggest problem we see here with cam changers is that almost nobody knows how or takes the time to check the degreeing. Also the timing requirements change,sometimes jetting, and carb cfm or manafold design too.If the impeller is too tight (AA),the motor can never see the rpm range that the new cam will make its power gains at. If the new combination is not THOROUGHLY worked with, oftentimes a more powerful combination is given up on before its true potential is realized. We have run MANY Comp Cams 280 and 292s in jet boats and ALL have run faster with the proper setup changes. Don't give up! Ask more questions! Pay someone if you have to! THERE ARE NO HARD AND FAST RULES REGARDING DURATION AND COMPRESSION, CIRCUMSTANCES ALTER CASES! As far as Edelbrock goes, the reason the Performer fits with an HEI, is because THE RUNNERS ARE WAY SMALLER! So is the plenum(gosh I LOVE using capital letters!), That affects cylinder filling and rpm range of operation. Would you believe that you can run 276deg @.050 with 9.5 compression an AA impeller and go way fast too? (the smart guys will recognize this as bait and know not to get into that discussion) wink :) :) TIMMINATOR

[malcolm]

So why do all the bigger cams say "increased compression ratio required"?

[Jet City]

Timinator, if you see no "hard and fast rules between duration and compression", what guidelines do you use for selecting a camshaft. Certainly there must be more to your cam selection process than just picking a super big cam and tuning until it works. There is certainly a point of deminishing returns in regard to duration. If you want to continue this mabe we should start a new thread, no need to hi-jack Dgie's thread. I'd love to hear what others have to say on this too.

[TIMINATOR]

Typically that's just a disclaimer to keep you from getting too pissed at the manufacturer if you don't know all you should about the cam selection process. They hope that you will at least ASK SOMEONE with more knowledge to help you. If you don't then they can say you should have. Most guys can change a cam but not compression so they will have to go to someone more knowlegable, like a machine shop. Compression is a great bandaid for other things lacking,(oh you didn't go high enough compression, THATS your problem) that's the thinking anyway. :D TIMMINATOR

[flat broke]

to a point I agree with timinator, if you are willing to make OVERALL setup changes (impeller, loader, shoe setting, ignition timing, valve timing, A/F ratio etc, you can probably get more out of the 280 in the long run. The biggest problem with jet boats is that once your HP absorbtion curve for your impeller intersects with your HP curve, you're done from an RPM standpoint. In a V'drive, you would just make tradeoffs between your gear ratio and your prop to get the motor up into its powerband. In a 18-19' jetboat with a efficient impeller setup and a low compression motor, you would have to cut the hell out of the impeller to allow the motor to wind up to its new powerband with the larger cam. The tradeoff would be sacraficing your holeshot and overall thrust velocity/volume to get your motor to spin more RPM. A good example of this was seen in a blown injected deal that was spining above 7k with a blocker loader and a C impeller. By changing the pump setup(larger impeller and let more water hit the impeller) he couldn't spin as many RPM, but because of the increased efficiency of the pump setup, his holeshot greatly improved, and if I remember right he lost something like 1mph in exchange for reducing his RPM by something around 4-500 RPM. Unless you build with a plan, I.E. I want to go x mph, and that takes x RPM with x impeller which in turn takes x HP, you will end up making tradeoffs against various aspects of your setup. Believe me, I'm going through it right now, and I knew better when I started. :)
Chris

[Jet City]

I have created a new thread for our cam discussion. I think its a subject worthy of its own thread. Unfortunatly, I will have to wait several hour to participate. I figured we'd keep this thread intact for helping Dgie.
http://forums.***boat.net/ubb/ultimatebb.php?ubb=get_topic;f=11;t=003972

[TIMINATOR]

Sorry Jetcity,I was typing when you posted.CRITERIA:Stock motor or... square decked(BHJ), line honed,zero decked,ported heads,manafold type,carb size,impeller size,engine size,exhaust type and size,intended use,power adders?,compresssion ratio,piston construction,valve size,oil pan size,oiling system modifications,how fast you are now,how fast you want to be,valve to piston clearance,valve type,retainer to guide clearance,valvespring pressure,and lift capabilities,aw hell someone start a new thread! :) :) TIMMINATOR

[dgie]

sooo what cam should I use? :confused: I was on the realolds power board and the 2 that were brought up most of all were:
PAW
818-678-3000
P/N 10333 - 204°/214° cam $49.95
P/N 10334 - 214°/224° cam $49.95
what do yall think?

[flat broke]

You'll need the lift numbers for those cams as well before anyone can begin to help you out with them.
Chris

[Jet City]

dgie:
sooo what cam should I use? :confused: I was on the realolds power board and the 2 that were brought up most of all were:
PAW
818-678-3000
P/N 10333 - 204°/214° cam $49.95
P/N 10334 - 214°/224° cam $49.95
what do yall think? OK, I think we are still lacking info to make a good decision here.
Here's what we know-
18' hull
455 Olds (low hour and .030 over)
Jacuzzi 12 WJ
Torker/750 Holley
Bassett OT's
Here's what we need to know (IMO)-
Engine CR (or static compression)
Head castings (valve sizes, ported or no)
Impeller cut (A,B,etc.)
Cam specs (more info on those PAW cams, lift and LSA)

[dgie]

Not sure about everything else except:
The heads are not ported, they are stock J-heads with heavy duty springs on them. Compression is going to be tough it is tore down, so I can not hook up my compression gauge and get those numbers for yall. Maybe someone else with a stock 455 and j-heads can chime in on the missing information.

[malcolm]

dgie,
Someone on ROP mentioned you had low compression pistons, did he know what he was talking about? Do you have the part number off them? Cast or forged?

[dgie]

Malcolm I think that guy knows what he is talking about (beast455) the other guys I do not know. Is there really any reason that these 2 cams would not work. I do not know what the true diffrence between a marine cams and the regular automotive cams, and if there are truelly any, except price. Beast455 told me before that they are just stock regrinds nothing special. The cam you are talking about is that for a 455 or a 403? If it is for a 455 is it the same as the ones he mentioned above if not what is the diffrence?As for the compression I believe it is a low compression engine, he keeps saying it is.Also I think the pistons are cheap so I assume they would be cast. Also there are no part numbers.
[ September 18, 2003, 10:01 PM: Message edited by: dgie ]

[dgie]

[ September 18, 2003, 10:00 PM: Message edited by: dgie ]

[malcolm]

Cams in an Olds will interchange between small and big blocks. The cam I'm running in the 403 is the same one Colormegone from ROP has put in 455 powered boats before. It's called a W31 cam on the Olds boards, they put it in the hot W31 350 Olds engines around 1970. It was also the factory hipo marine cam used in 455s in the 70s.
Have you looked at the links posted in the camshaft 101 thread? A lot of reading, but a lot of info!

[dgie]

how does that cam you mentioned differ from the cams above that Beast455 recomended? is it bigger, smaller, or?

[TIMINATOR]

DGIE: the STOCK 455 Olds jetboat cam is 214/218 deg @ .050, the replacement pistons for cars have a dish of about.210 depth and are cast, the jet boat pistons were all forged and had a dish of only .130, giving a higher compression of 9.5 to 1 nominal. If a 280 Comp scares you at 230 @ .050, try a Comp 270 at 224 @ .050. By now its unlikely that the motor is all original, but thats what it had when it was new! Use a big(10 qt.)pan and over the winter have an Olds Guru modify the oiling system and degree in the cam and enjoy it! TIMMINATOR :)

[Jet City]

I found my PAW catalog, here is the cam specs for your viewing pleasure.
p/n 10333 204-214 (@.050) .448/.472 on 112 LSA
p/n 10334 214-224 (@.050) .472/.496 on 112 LSA
p/n 11348 224-234 (@.050) .496/.520 on 112 LSA
p/n 11349 232 (@.050) .445 on 113 LSA
(I beleive p/n 11349 is the W-31 cam)

[TIMINATOR]

I would prefer a single pattern cam at 108 or 110 deg lobe separation, and 224 to 230 at .050. Its your boat! DEGREE whatever you put in! P.S I used to have a Taylorcraft 18 with a 455 in it! Happy roosting! TIMMINATOR

[dgie]

Timinator the engine is relatively stock, but I do have the oiling kit already from Mondello, which includes a High flow oil pump oil restrictors, and 12 Qt oil pan. I also have oil restricted push rods from Smith Brothers. I have that oiling problem nailed down and am looking forward to getting this cam shaft nailed down also.
[ September 19, 2003, 12:59 AM: Message edited by: dgie ]

[malcolm]

dgie,
The W31 cam has .474" lift and a 232 duration at .050" lift. I hope you're getting a little better at what all these numbers mean. From what my buddies and I used to say, the 230 number is where the cams start to get lumpy on the idle. I did up my compression some with early heads to run the cam. We still don't know all the specs on yours, but I would say mine is smaller since your lift is over 500.

[dgie]

I am going to run down to where my boat is later on this afternoon and play around with the degree wheel. I need to get a grip on pulling duration figures off the cam. I think that will help out a lot and bring things into perspective a little more. I can not believe how complicated cams can get. I thought fiber optics was complicated with measuring wavelengths and bit error rates.

[Jet City]

dgie:
I am going to run down to where my boat is later on this afternoon and play around with the degree wheel. I need to get a grip on pulling duration figures off the cam. I think that will help out a lot and bring things into perspective a little more. I can not believe how complicated cams can get. I thought fiber optics was complicated with measuring wavelengths and bit error rates. Mabe you can get a fix on what pistons you have while your there too. Flat, dish, etc. then we could get an idea of your CR.

[dgie]

The pistons are flat, with a very shallow dish

[Cas]

Dg,
Try these numbers for a cam or maybe ask the guys on ROP to see what they think.
in. lift - .500
ex. lift - .500
dur - 296 on both
Lobe cent - 114
ivo - 34
ivc - 82
evo - 82
evc - 34
The TQ curve is pretty flat with it's peak around 4200. The HP peaks at 5000 which works good with your set-up. We installed a similar cam in my son's 455 and he's real happy with it.
He has what sounds like the same pistons as you which were figured out to be about 8.25 to 1 CR.
The only real difference is his is +60 on the bore.

[dgie]

Thanks Steve I will check it out. I am still working on getting this duration thing down. The lobe center of 114 is something new for me. What I am finding standard is 110 lobe center.

[TIMINATOR]

Wider lobe centers give a better idle and a broader torque curve,fine for a mild street car. A jet ONLY NEEDS TO MAKE POWER AT AND SOMEWHAT UNDER THE RPM THE PUMP MAXXES OUT AT! Narrow lobe centers make a narrower powerband with a HIGHER POWER PEAK,just right for a jetboat. On a 454 squareport crate engine turning an A impeller at 4800 rpm,changing the cam from the factory 224/224 at .510 lift and 115 lobe separation to a Comp Cams Jetboat grind of 222/226 at .525/.525 and a 110 lobe separation netted a change of 300 rpm! When I replace the crate cams now, I order them with a 108 lobe separation and the gains are even higher! With a tight lobe sep.it is much more important to have the correct cam as the power band is so much narrower,also the valve/piston clearance becomes closer.Your engine builder better know JETBOAT motors or he won't be nearly as much help as you think! You don't go to a Dentist for a foot problem!Enough for now,I'LL be baack! TIMMINATOR :D :D :D

[dgie]

Ok here is the numbers that I have come up with, anyone who can figure this one out please chime in. I am trying to figure the duration of this cam, kind of a learning curve for me here. I started on the intake lobe. The number that I came up with is 19 degrees @.050 open and then I continued and at .050 before closing the wheel read 156 degrees. Then I moved to the exhaust and the opening event at .050 was 152 degrees and closing was 22 degrees @ .050, now what? does it look right? I read along in the Mondello book and the numbers that they came up with were much lower
they came up with something like 20 degrees and 48 degrees for opening and closing event of an intake valve then they added 180 degrees. ?????

[ralph]

jawdrop The main reason for stating higher compresson required is the biger cams have such a low vacuum at low rpm the higher compression adds a little to the bottom end, and when the extra compresson is not needed for the engine the extra cylinder compresson is lowered by the speed of the engine at very high rpm's lack of flow in the intake usually is the culprit. and at the high rpm any probability of detonation is lessened because of the lowere load ont he engine as far as lugging is concerned.

[malcolm]

What? Sorry ralph, but none of that made any sense to me. I think compression at idle is going to hurt as much as it helps because most of the extra power made is needed to help compress the next cyl. Just my thoughts.

[dgie]

glad to see I was not the only one scratching my head on that post from Ralph. Malcolm go back and recheck my post on the ROP board I really want to know how you got those numbers.
[ September 21, 2003, 12:00 PM: Message edited by: dgie ]

[malcolm]

I was just there and saw your post, but looks like the others have it covered. Does it make any sense yet? :confused:

[Jet City]

dgie:
Ok here is the numbers that I have come up with, anyone who can figure this one out please chime in. I am trying to figure the duration of this cam, kind of a learning curve for me here. I started on the intake lobe. The number that I came up with is 19 degrees @.050 open and then I continued and at .050 before closing the wheel read 156 degrees. Then I moved to the exhaust and the opening event at .050 was 152 degrees and closing was 22 degrees @ .050, now what? does it look right? I read along in the Mondello book and the numbers that they came up with were much lower
they came up with something like 20 degrees and 48 degrees for opening and closing event of an intake valve then they added 180 degrees. ????? The values you've come up with don't make sense to me. Unless those values (intake side) are 19 degrees (BTDC) and 24 degrees (ABDC) which would be past the 180 degree mark and count down to 156 degrees on the wheel. If this was the case your cam would measure 223 degrees at .050. I can clarify where the added 180 degrees came from though, here is an example of opening events at .006 from my Comp 280H cam card...
Intake 34 BTDC(open) 66 ABDC(close)
exhaust 74 BBDC(open) 26 ATDC(close)
So for example, on the intake stroke the valve opens (.006) at 34 degrees before top dead center (BTDC) travels 180 degrees through the intake stroke, then closes (.006) 66 degrees past past bottom dead center (ABDC). So for this particular cam, there is 280 degrees of total movement from .006 open to .006 closed, which is the advertised duration. You whould see the total 280 degrees if measured with a degree wheel (moving in the clockwise direction).
For your cam it would break down as follows (if I'm interpreting the values you gave correctly) measured at .050.
Intake 19 BTDC(open) 24 ABDC(close) (223 @ .050)
exhaust 28 BBDC(open) 22 ATDC(close) (230 @ .050)
I'd go to the other thread I started "camshaft 101", somebody left a couple of links that I think may help you figure a few things out.

[Jet City]

dgie:
glad to see I was not the only one scratching my head on that post from Ralph. Malcolm go back and recheck my post on the ROP board I really want to know how you got those numbers. Numbers? ROP = real olds power?

[malcolm]

Yeah Scott, we got the same stuff going on at Real Olds Power too. :D

[dgie]

Jet city I am still not too sure how the numbers make sense. I am still digesting all this info. Go to the ROP board and look for my thread under my screen name "Darren" you will see what they came up with there. What I got so far is that my degree wheel is not double marked like most are evidently. I am going too have to keep thinking on that one.

[THE BOSTON SIDEWINDER]

HI TIMINATOR, THANKS FOR THOSE 454 CAM SPECS! CAN YOU MAKE THE SAME BASIC GENERALIZATIONS AS FAR AS COMPARING STOCK WITH AFTERMARKET CAMS ON THE 8.2 (502 CU.IN.)ROLLER ENGINE(GEN VI, 1998 4 BOLT)? THANKS,...BILL.

[TIMINATOR]

Boston; you betcha! they have wiiide lobe centers on the hyd.RLRs too!Same basic numbers but a LITTLE faster ramp rate. XR276HR (01-416-8) 224/230 .510 works for an good gain, or XR282HR (01-418-8) for more power with a lumpier idle. Both work with stock springs! OOOOPS, they are made by COMP CAMS! If you want to change springs,retainers,locks,and cut the valveguides down about .100 you can go bigger lift, and a bigger cam. To cut the guides down you have to remove and dissemble the heads. On SOME motors you can go to .530 or .540 lift without cutting anything,but you BETTER CHECK IT FIRST! TIMMINATOR :) :) :)