What would it take to make my 502/415 hp mpi's into 500 hp
Going to have motors rebuilt and thinking about up
Grade

I think you can get by with cam and piston swap (more c/r 9.5-1) Should be 500 plus hp.

cam change, dart intake and 800-850 carb, exhaust...easiest and cheapest way to to that power...sure there will be others baulking at removing EFI....now you can do it with the EFI but the cost is a lot more...

...and you can sell the complete EFI system for good money.

A camshaft and good exhaust -- Bob Madera (Rmbuilder) -- if this isn't your first phone call, you are making a mistake. He'll help you through the whole process, I worked with him this summer and due to his sage like advice I avoided some serious mistakes, and he blew my horsepower goal of 500hp out of the water, with VERY basic parts.

http://www.marinekineticsonline.com/

EDIT: Well hold on if you are referring to the 415, that's prop shaft horsepower, the motor is 450 stock I believe. To get to 500 pshp you'll need more than a cam...but not much...

Exactly what you are looking for.

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

+1 Forgot about that thread, perfect.

You can get more power with the carb with less work (more aggressive non-EFI compatible camshaft). but keeping EFI sure is a nice option and you already have it so it's not like you are deciding which way to go. And those are phenomenal #'s with very minimal changes.

Yes just checked out thread that is what I am looking for

unless I missed it....never did answer the "cost" question ???

I don't even see a cost question, unless I missed it

What are you looking for?

EDIT: Oh... I think you were referring to the other thread...if you are, just ask over there.

Manifolds - $2500 new but you can pick them up fairly cheap used and if you are going to buy used manifolds, Stainless Marine are the ones to buy.
Roller Rockers -- $300-400
Custom Cam -- Call Bob
Porting -- No idea
Tune -- No idea

These last three may vary quite a bit, you'll need to get those numbers from the guys that do it. But I'd guess the last two wouldn't cost any more than going carb (intake, carburator, extra's for the fuels system etc.), However, you could go much more aggressive with the cam on a carb motor.