454 Repower
 

Repowering a 98 Eurosport 233 sport.
Mark IV block, scat rods, alum rect port heads 225/188 valves, domed pistons yielding 10:1 compression (running 93 octane), air gap intake, 1410 carb, electric fuel pump, Imco power flow exhaust with SA risers, 222/226 114 LSA Hyd roller cam. My cam grinder says I should be pushing 500hp but cam sounds to small to me?? Since I'm running shorter risers and captains call reversion was taken into consideration. He swears the motor will still make good power but I'm concerned about that cam grind?? I want dependable power to 5200rpm and at least 450hp.

With that cam, I think youre leaving a lot of hp on the table. I would guess you might make 420hp or so.

Get longer risers and bigger cam. Otherwise, no reason to have to run that compression. To have to run 93 octane for such a mild motor seems like a waste to me...and maybe a hardship if no 93 octane on your body of water.

Edit in: since a switch to aluminum heads, why not some good aluminum oval ports ?

My opinion. Other's may vary.

Who is your cam grinder?
If the cam was custom from a knowledgable source, he specified it that way based on the data you provided him ( engine and boat data )

It has been my experience that good custom cam guys know what works with what you have and how you use the engine.

Whats the lift on the cam?

Not sure I'll have check I can't remember what he said on lift.

Oval port is what I was leaning towards but builder said only 20cc bigger on the sqaure ports and it would flow better on top end

If truly 10:1 compression, I'd agree that cam is too small

How does compression ratio affect cam sizing/selection?

Dave's Radiator Shop ?

A cam with more duration / valve overlap needs more compression to maintain cylinder pressure as both valves are open at the same time for a longer time.

Guys with more intricate understanding of cam design can elaborate but, that's the "cheap and dirty" explanation.

As you move up in cam duration, you get into later intake valve closing points. When the intake valve closes later, some of the cylinder pressure is bled back into the intake manifold, mainly at low engine speeds, since there is simply more time for it to do so, when things are moving slowly.

For example. You can have a 8.0:1 engine, with a very short duration camshaft. That engine may build 150psi of cranking pressure. If you raised the static compression, to say 10:1, with that same cam, you may see 200psi of cranking pressure. Now, if you have a 10:1 engine, but go with a longer duration cam, you may see 175psi cranking pressure. With that same long duration cam, in the 8:1 engine, would drop the cranking pressure to say 125psi.

What happens when you have to much cam, and not enough compression, is the engine becomes a real turd, until the RPM (time lapse), increases to a point that the pumping losses arent as drastic. In other words, thats why some engine combos like that, cant get out of their own way until 4500RPM, idle like crap, etc. And vice versa, if you have too much compression, and not enough cam, your cylinder pressures can be very high, which could mean lots of power down low (but possible detonation), and a very limited upper rpm range.

Compression ratio and cam choice, go hand in hand. IMO, a high static compression, short duration cam, is a bad recipe for a marine engine. Like a 10:1 setup with a short cam like the OP has. IMO, that cam should be used with no more than 9:1 static at most.

The man to talk to on this stuff though is Bob Madara. IMO, if the builder spec'd that cam, with that compression for a pump gas pleasure marine engine, I'd look elsewhere for an opinion, and I definitly wouldnt want to lock the timing out on something like that.

Sent Bob a message, also got the cam card from erson cams that was spec for my build. I have to agree cam is too small. Idk what the heck they are thinking. My biggest question is will a cam in the 224/230range on 112lsa revert water thru Imco SA risers? From what I'm reading it should be ok but anyone running similar cam specs with short or stock exhaust?

What heads are they?

I'd discuss the cam selection and reversion concerns with Bob.

I'm not a big fan of the edelbrock carbs, but thats just me. "20cc bigger on the intake ports" flow better statement scares me.

It sounds like you need to hook up with the right people to help you out with this engine build. You goal is a very realistic one, but parts combo needs to be a #1 concern.

I'm running 231/235 on 112 with a touch of advance to prevent reversion with my risers. I want to get some dry tails and go bigger. This is on a 496 stroker with sound select gils.

He's saying that the larger intake runners on the intake will flow better on top end. I suggested oval ports for air velocity but he said the rect would flow better on top. Heads are PC3021's.

ewww. Procomp heads. Besides the quality issues with them, they are already too large for your engine. Going "20cc" bigger, will do nothing for you.

So we got a 10:1, procomp headed, edelbrock carbed, undercammed, setup going here.

HEI Ignition?

I'll say it again...Dave's Radiator Shop ?

Why trash the guy over an engine the money has already been spent on .If Op asked the builder to up the cam roughly 10 degrees intake and exhaust ,It will probably be fine ...I don't know crap about pro comp except what I read ....OP already owns them .I'm assuming he doesn't want to start over ...Idle rambling

He said repowering and also is questioning the cam and eluding that he may want to change it, therefore I did not take it as a done deal.

He put it up to the public....so one must be prepared for less than pleasing answers, even if it is mostly truth.

'Trashing' is more harsh than what is going on here. Plenty examples of that in this forum.

Shouldn't have used the word trashing ,but my take was engine was together .I will agree not the best thought out combo ...

Well I was just posting hoping that someone with some experience with and or actual knowledge of cam size / reversion with wet exhaust could weigh in.

Who's the engine builder ?

Is the engine built yet ?

bob specked some cams for 2 builds im doing.454,s with 177 blowers,gill wet exhaust.226I,235E on a 114 lsa.

The OP said, "my cam grinder" leading me to believe he had a custom cam ground based on his application.

Who is the cam guy or is the "cam grinder" the engine assembler picking a "shelf" cam?

The cam picked will be fine for not reverting.

The compression and heads will want much more cam.

So, IMHO, you choosing the 454cid and the exhaust being used, you'd be better off with good oval port heads and 8.75 - 9.0:1 compression. The cam being chosen would be still fine and maybe better on a 112LSA.

Oaks machine in Logan ohio. Cam grinder is Eric at Erson Cams. That's who he has used for years.

I have not personally talked to him yet. I'll know more tomorrow about how or why he spec that cam

Dennis moore suggested 224/230 on 110lsa
I would rather keep compression up and use a larger stick just need to know where I can go without sucking water back. I think dennis is right just may add some lsa to be safe.

110lsa??? No!!!

I agree with Mild!
I try to stay out of these cam threads, but I have to add my 02 cents. 112 min. LSA you can stand to add a bit of duration depending on the exhaust timing closing event.. FYI I have had good results with reversion if you spread the exhaust LSA further. A custom grinder can stagger the intake LSA and exhaust LSA to help with the reversion. ALSO just my opinion ditch the Eldebrock! Cams are subjective to so many engine variables that I suggest as many others have said to get another opinion.

ICL and ECL. Deg between the two is the LSA.

Just clearing things up to avoid confusion.

http://www.chevydiy.com/wp-content/u...014/01/811.jpg

Exactly, maybe he's thinking of a 4 pattern cam?

That's from there website.....

So this guy can make your John Deere haul azz, but has he ever seen a boat?? Nowhere on his site does it mention marine.

You might want to find a shop a little more performance marine oriented so you only have to build this motor twice instead of 3 times,

Nah, just lingo mess up. Thus why I'm keeping it straight so other's don't get confused.

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A lot of people have basic understanding of lsa, but not intake centerlines (ICL) and Exhaust Centerlines (ECL) and that they mathmatically make the LSA #.

Correction
 

LMAO! I logged tonight first time since Monday night. Sorry I can't post, bid on Ebay, PM members, and answer emails at the same time, and proof read my post!! Corrected Quote above!! My experience with this has been in My blown 454 years back, we had a reversion issue(with lightning headers) move from a 114 to a 115 LSA (Reground the same cam) same duration/lift cured the problem! At the time we were going to back the duration down 2 degrees(as it was minor amount of water) but we tried the wider lobe separation and it worked. Main point being even with the lower duration #s you posted I would still go to at least a 112 lobe separation.

Thanks SB for getting on that right away!!

Quick2500 I was considering a 4 pattern cam for my little 302 Ford this spring but they are pricey!!

If the 4 pattern was worth it the guys that have all the money would have them in there motors and they don't.

I know the feeling. I've typed some bozo stuff while on the phone/emailing/and typing on a forum.

Don't worry about the 4 pattern cam. Save your $$$.

Yeah I bought a flat tappet hyd for my 1968 302, wanted the original type cam just went a bunch bigger sounds real nice!

PS I lost my items on Ebay also!!

This spring being this past spring, not coming spring,

I found out the hard way that you have to be careful comparing cam profiles between a flat tappet design and a roller design. You could have two cams with identical LSA and duration at .050 lift, with one being a hyd flat tappet and the other a hyd roller, and you could have different tendencies towards reversion depending on the actual lobe profile. For one thing, a roller can have a much more aggressive lobe profile that gets the valve up off the seat much more quickly, so you really need to look at the timing events listed on the cam card to predict how the cam will behave in regards to reversion. Add to that other factors like compression, cylinder port efficiency, displacement, crank stroke, and the angle of drop for the exhaust, and you can end up with some surprising results when it is all put together if you only base your cam selection on LSA and duration.

I'm running what should be a very docile hyd roller (226* / 230* @ .050, 114* LSA) in a 489, and that thing would shred a dollar bill with it's reverse exhaust pulse at idle if you held it up to the collector. I think I had the perfect storm of longer stroke accelerating the piston, very efficient exhaust ports (AFR heads - remember, they can flow in both directions), and header design contributing to this.