Just to update this old thread that's been brought back up. This motor is still running but has had a couple cam swaps. The original cam had reversion issues that caused some rusting in the exhaust ports. The only cam I had laying around for a quick swap at the time was a zz502 cam. It made a little more hp 15-20 ish and had a broader torque curve, but performance in the boat wasn't much different. The idle was a fair bit rougher then the first cam and the owner didn't really like it so we swapped that out the following year for an Erson 230 - 236, similar to a 500efi cam with a bit more lift. That really woke it up, making 570hp and picked up 3mph in the boat. It's still a bit of a lumpy idle but very solid.

Alex. Its been a while since you started that great old thread about FI. Surely some changes have occurred. How bout a part 2 on the latest FI setups available?

What springs did you use?

I was planning on the exact first setup you did and keeping the MPI. I have the same Stainless Marine exhaust and Silent Choice as well. So Alex am I correct in assuming I will have issues with reversion as well with the first cam choice? What now?! lol

Comp 929

It depends on a lot of things. If you haven't purchased the cam yet, there are definitely better, and cheaper options

I haven't purchased anything yet so I need to get this figured out soon. I'm glad you bumped this thread the timing was perfect. I would have hated to have made another mistake... Can you set me up with the things I need to finish this project the right way? Thanks for the reply

Keep in mind, after doing the typical mpi intake mods, once you upgrade cam and heads that there IS hp gains to be had in using biggest bored out throttle body you can find and best flowing air cleaner, like i have previously mentioned, i made 563 hp from highly modified mpi intake and throttle body on a flat top piston 502 (slightly less comp than stock) w lightly modified 088 heads and 500efi cam, 657 hp from 8.4-1 540 w cncd afr heads and over 1100 hp blowing thru a mpi intake on a 540. If you have a 98 to 01 mpi w the magetti marellii fiat injectors as long as they flow evenly they will easily support 600hp. I have yet to see 8 of them BEFORE cleaning and flowing on my injector machine that match, new ones dont necessarily match either so i highly recommend having them cleaned and flowed, if too many are junk the siemans deka shortys are a drop in on 98 up/mefi 3 mpi intakes. Tpis has by far the best throttle body mod for these, its very reasonsbly priced , it does require plenum opening work, i tried dynoing a motor without making plenum match it perfectly and it really disrupted air distribution, Smitty

My engines are 1995 502 MPI mags, V-belt, VST, MEFI-1, non rollers. My other issue is I have nobody in my area (that I know about) to reprogram my computers or tune them on dyno which is why this thread was so appealing to my situation since it was all bolt in and go. Throttle bodies as you have wrote about would be nice and at minimum, I was also planning on sending my injectors somewhere to have them cleaned and flowed like you say since they are old and I could have issues...unless all of that messed with the potential tune? I already have the best flowing flame arrester according to your dyno results which is about all I have going for me at this point lol.

Just got my hp 500 efi tpis throttle body for my next mpi dyno project, a very highly modified 500 efi intake on a 540, beautiful piece! The cool thing with the 502/454 mpi throttle bodys they do is they redo yours so its half as much money as buying one, I see its 279$ on their website, Smitty