502 rebuild/ upgrade
 

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.

For reference here is the carbed combination I had assembled this year.

- Stainless Marine Manifolds (these were already on the boat)
- Rectangle heads with stock valve size and a valve job (matched to intake NOT ported) with Performer RPM intake and 850 Holley 80330 vacuum secondaries, one jet size down on secondaries
- Converted Gen V 502 Block to roller, honed only not bored -- Bob Madera (RMBuilder) Custom Cam
- Stock JE700 pistons with new rings, stock rods.
- 9.25:1 compression up from 8.75 (.010 off the block and .010 off the heads)
- 1.7:1 Scorpion Roller Rockers

539HP and 569TQ full dress with wet exhaust. Peak power was ~5100

I am sure I left some power on the table -- I specifically told Bob this was a family boat and drive-ability and good idle characteristics were the priority -- he is the man and should be your FIRST phone call, he was EXTREMELY willing to work with me to get the RIGHT combination.

Who was able to dyno your engine with wet exhaust?

Roush.

Thanks, my PM was the same question.

Bob M.
 

I have nothing but good things to say when it comes to Bob. He truely cares about not only his customers but his potential customers as well! I am very close to ordering up my cam, lifters, etc... from him and have talked to him several times as my build has changed direction a couple times. I have decided to have my heads flowed and will be giving him a call shortly after that to have him do a cam for my app. He is extreamly knowledgable, knows what combinations work well together and has always taken the time to listen to me and has also (which imo is just as important) given me his honest opinions as to why one part I might be planing on using may not work as well as another. Personally, I will not go to anyone other then him when it comes to the valvetrain that's going into this motor I'm currently building. I'm sure there will be several other parts such as bearings, rings, etc... that I will take his advise on and more than likely purchess from him as well.