I have a 415 horsepower 502 and would like to get another 100 hp out of it. Any suggestions on what I should do? Head work, cam, exhaust? Is the merc exhaust ok with another 100 hp. Will I have reversion problems with the cam I will need? Thanks for any input.

I built a stock 509ci engine using all stock parts except the valve train. I went to Bob Madera @ Marine kinetics who set me up with an entire valve train setup but pushrods. Springs, retainers, locks, roller rocker arms, hydraulic roller lifters, cam and he recommended an air gap manifold & 850 quick fuel carb. With a DUI distributor this engine made over 500 lbft of torque from 2800-5300rpm & with a 1" spacer under the carb it made 512hp@5300 but would wind to5600 using dynoroom headers. I am pretty impressed for having to buy new stuff I spentjust under 3G for a turn key stump puller that will live for many hrs. Randy

Stock Merc exhaust will revert water with any significant cam upgrade.

Stainless marine or EMI thunder should be ok & are mostly the least expensive. Possibly Lightning headers, not as expensive as CMI, etc. Randy

look at he hp 500 / 502- 500 check the difference in cam exhaust heads carb . i believe the 525 use edelbrock performer heads with cmi exhaust .

Here you go
http://www.offshoreonly.com/forums/d...e-results.html

Mine has a pair of Graffig "cool chargers" . Similar to superchargers. It took mine up to 600hp. The company was sold to O2 Force (Powerdyne). Works good.

I’m also in the same boat as you with my 509, 088 heads, airgap & 496 manifolds. I was surprised to read here on the forums a guy running the 502ZZ cam & stock exhaust without reversion. Also read the original HP 500's (731 cams) had Gils and silent choice? I haven’t decided witch cam to use ( may just re use my 502 HO cam) but thought my 496 manifolds would be an improvement over the above exhausts with either cam.

Thanks for all the input. I'll have to kick it around and see what i decide to do for a little winter project. I would really like to be going a bit faster next year.

ProCharger...

You're welcome