We build a 540ci version of the 500EFI. We modify the intake, port the stock cylinder heads, install a custom grind cam, and retune. With Iron GM heads the HP is between 630-640. With aftermarket heads we are very close to 700HP. The limiting factor is the intake manifold. Check out PB mag this month for more info.

Matt Beddoe
Derebery Performance Marine
www.dpmpower.us

New question.....what's the highest compression ratio I can safety run 89 octane with this setup? I don't want to "have" to run 93.

9 to 1

ask stecz how to make big power he'll tell you ya need 800ci to make 600 doggies

He just needs the big cylinders to get his big head in there during assembly.

Any more input? Now I'm realizing 93 octane will be a must.

Ported Dart Pro 1's or any other good Aluminum head, low CC chambers, 9.5-1 comp. with a good cam!

Try this, 87 octane http://www.pfaffengines.net/challenger600na.shtml

Thats a nice setup! I would call and see what they want with your engine as trade ! You don't need the exhuast, your CMI's are better anyways. They state 600 hp, but probably on a dyno. May be less in the boat. But still good hp !

Nothing like a brand new engine :-)

jeffy called yesterday, over 600 hp and WELL over 600 tq, on a 100 degree day 100% humidity with not so efficient breathers on it. Rev limiter at 5500, will take it to 5800 and be exactly where it needs to be.Should be 625 hp and 640 tq