502 MAG MPI Cam swap
 

Bought some custom roller cams with .578" lift on the intake and exhaust, and am looking at options for springs. The motors only have 70 hours on them, and the only reason I am doing this is a bought a bare hull and motors, putting it all together and going to run it. What I am wondering is what valve springs do most people go with on a camp like this with stock lifters? Comp 929-16's? Do these fit in the stock valve spring pocket? I will be running the ARP studs to convert to adjustable valvetrain, along with Comp Moly rockers, and some 1 piece moly pushrods. This will all be accompanied by Stainless marine exhaust with dry tails and will be ordering MEFI burn. With that, is there any updates to do to the stock timing chain set, if its worth it?

Also, does anyone have a combo like this that would like to share their MEFI file for my base to start at? I beleive these are either MEFI 1 or 2 computers.

Thanks in advance!

Do you have a cam card for them, or do you atleast have the full specs for the cams?

Hopefully you do, and then you could call Comp and PAC and tell them what you have and see what they say you need as far as spring pressures, part numbers, etc. Then you can call Bob @ Marine Kinetics and talk to him, pick his brain and see what he has to offer and see if what Comp and/or PAC said is going to be ok.

http://www.marinekineticsonline.com/

my advice is to just call bob and not waste your time with others.

Already have the cam card, he suggested at least 135lbs on the seat, and at least 360 at full lift, in which I believe the 929's will get me there.

Changing cams out now is not an option, these were custom ground and should work well, just trying to find the exact spring I want, that is why I posted here.

Are you utilizing the stock injectors? If so keep an eye on duty cycle.

If you are doing the tuning yourself I recommend getting the engine running at idle with the stock tune first. THEN start making small changes. ONLY change one variable at a time. 90% of the tune changes will be in the fuel table only. The stock tune should get the motor safely lit off (no load idle and off idle rpm range). You must have wide band O2.

Cam specs and parts, talk to cam and builder guys. I'll offer no advice there.

Good luck.

I don't think I will have any troubles tuning, already have a Innovate wideband from my previous project, stock injectors I beleive will be good enough for my 50hp hike that I will hopefully gain. More so looking for the hard parts and how guys set them up, I can't find any information searching and didn't really want to be a experiment; And I don't want to call engine builders and waste their time, was hoping someone did a parts swap like this..

Bob doesn't mind you calling and he is an authority on the subject. It will be much less of an experiment if you run it by him before you start. Good luck.

Does anyone know the stock installed height of the stock valves then? valve stem size? That way I can order parts before I tear both these motors apart.

Listen to what is being said here:

Call Bob at Marine Kinetics. Do exactly as he suggests, and buy all of your needed parts from him. His prices are competitive with any one, and his knowledge and advice is priceless.
He will save you thousands of dollars in the long run.

Steve

You'll find the wide band invaluable. My guess is 50 hp bump is likely within the capability of the stock injectors.

Good luck.