Rebuilt Engine Help Needed
#11
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[QUOTE=shawn]The cam is a custom grind from the engine builder. Lobe seperation is .110 on the intake side and .119 on the exhaust.
These numbers can't be possible. Check the #'s and post the correct ones. Maybe it will tell a better story of what the problem is.
These numbers can't be possible. Check the #'s and post the correct ones. Maybe it will tell a better story of what the problem is.
#12
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Sounds like you gave up bottom end and lower midrange for a little more top end. I also agree with the others that as a band aid approach you could advance the cam 4 dgrees more to try to recoup your bottom end with out spending much more money. Who ported your heads,Iv'e seen heads (even done it myself when i was younger)that were ported for big top end flow #'s that hurt the bottom end,especially with a little too much cam and too big of a carb(a common mistake someone that is used to building drag motors more than marine motors would make). cyl pressure is a good indicator of cam sizing also(old school thinking but usually still true) . I had a guy bring me a street/strip car that had a 10.25 compression ratio that was over cammed,he should have had 190-210 psi cranking compresion(from past experiences),it would barely idle and had a soggy midrange,i checked the cranking compression and it was only 155-160 psi,we advanced the cam 4 dgrees (still a band aid approach but cheap)and cranking compresion increased 20 lbs to around 180 psi,motor idled considerably better and gained throttle response and midrange. if you can,check your cranking compression #'s and post them,and If you do advance your cams could you post your before and after cranking compression or pm me with it,Smitty
Last edited by articfriends; 08-31-2004 at 11:57 PM.
#13
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shawn call me at 410 335 2226 CMS RACING ENGINES and we can help you get it stright . I'm in your back yard . my shop is in middle river md
#15
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Your compression ratio is WAY TOO LOW for that cam. Add on a single plane intake and you are loading it up trying to get on plane. (explains your black plugs) I don't know who built this engine but they should have known this would have been an issue. I mean for crying out loud that engine's power curve is dropping off at 5700 RPM. It should pull strong up to at least 6700. I bet is sounds good but you either need to go 11:1 CR or run it on NOS. NOS loves those long duration cams
I don't think advancing 4-degrees on the cam is going to help here.
Roby
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Roby
#16
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Originally Posted by TomR
When you do the math, a 502 running at 100% efficiency (I doubt your motor is much better than 90%) 502x5600rpm / 2 / 1728 = 813cfm. At 90% efficency that would be down to 732cfm.(#9022) Holly like yours was, just bolt them on and try it.
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C'mon this isn't a formula 1 engine. I'd say low 80s at the very best.
Roby
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Originally Posted by TomR
I was trying to be optimistic, but your probably right!
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Roby
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