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Re: New 502 is alot slower than my OLD 502??
As I mentioned in an earlier post,GM crate motors and Merc motors are two different motors.Cam and heads build the power.You should have 9:6.1 compression.I do not beleive your motor has that compression.As for the cam you need a offset duration cam with a CL of about 110 at your elevation.
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Re: New 502 is alot slower than my OLD 502??
Originally Posted by LAXBAJA
So this is strange. Its like when this motor hits 4000 RPM it falls on its face. |
Re: New 502 is alot slower than my OLD 502??
Well made some more calls today and we have found a cam that will turn this kitten into a cat. we are going to put a healthy cam, new springs, and remap the ECU. this is going to make around 470 to 480 HP. if I get the heads redone and the MPI intake from Arizona Speed and Marine. we can squeeze 500 to 525 HP. I hope this will give me the fix I need.
I'll keep you all posted on the cam change. thanx again for all the great info. |
Re: New 502 is alot slower than my OLD 502??
As I said in a prior post the GM crate motor and standard Merc motors are different.The cam and head CC's are not the same even though they both were built by GM.Your compression should be 9:6.1. and I doubt it is and that can be easily verified.
Your cam selection will need more lift on the exhaust side.A good CL would be about 110 to 112 advanced 4 degrees.Since you have the part number of your motor you can call GM tech support at 866-453-4123. Been there done that.Hope this helps. |
Re: New 502 is alot slower than my OLD 502??
Originally Posted by SB
With all the flat tappet cam issues I would pull a valve cover or two, start engine, and see if pushrods are spinning. If they aren't, you know your cam's are dead.
If they are spinning you could still have worn lobes but if they aren't you can be 100% sure they are done. The rest of my posts on this thread are for this thread. Doh ! |
Re: New 502 is alot slower than my OLD 502??
Originally Posted by LAXBAJA
I've contacted marine Engines INC. in Holliston, MA 1-800-786-7639. They wont tell me any thing. were they got the motor from, cam specs, compression ratio, heads, nothing.
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Re: New 502 is alot slower than my OLD 502??
Okay, more camshaft info for you.
The non-marine GEN VI crate motors GM 454/425hp + 502/450hp came with dual plane, rect heads, regular 502 shortblock, the normal 8.75:1 compression, and comes with the following hyd roller cam. GM# 24502611 Steel Hydraulic roller. Needs melonized distributor gear. 211, 230 at .050" .511" , .540" lift with 1.7 rocker 112 LSA I don't have more specs on this cam but can tell you it is pretty 'lame o' . |
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