Cam for 502 MPI?
 

Anyone done a successful cam upgrade on a Merc 502 MPI?

I have seen extensive intake mod's only, making a few more hp's but it really doesn't seem worth it.

I do have the possibility to remap but I wouldn't like to start all over. Some fine tuning would be ok ...

Alot of people have done it. To go big enough to notice a difference you would need to change springs and rocker arms, then get the ecu remapped.

You will also need to use a big enough cam to require a better exhaust if you want to see any significant changes.

See, we just spent $3000 for you!

Keep it up guys, it's for my customer - not me :D

Seriously, I was asked about the cam swap and I do have the possibility to remap myself but as long as he's stuck with the stock cast iron manifolds my advice is that it's not well spent money (or time).
A successful upgrade to me would include at least the exhaust ...

I would do the exhaust first. Why is he so bent on a new cam.? By the time you pull the engine and swap the cam you could buy some entry-level manifolds. That will net you your 1-2 mph right there and be ready for an even bigger cam when the time comes.

Skills? Maybe that's why he's the customer and I'm doing the work :cool-smiley-011:
I'm replacing both his long blocks due to a totally incompetent rebuild earlier that caused a real mess inside.
While at it he probably tried to find some cheap extra hp's but I've already adviced him against it since I also thought there is not that much to gain without the more expensive exhaust upgrade.
Just wanted to doublecheck with you guys if I've missed a secret or two.

Ahhh. That makes much more sense. I would expect that while you are in there you can stick in a little more agressive cam for 20 hp or so that will work with stock exhaust and then maybe reflash the ECU. I think that one of the guys on the Donzi site did that with a stock-ish type of exhaust. I would expect someone around here knows which cam will work. If not, I can check with him.

Comp Cams XE268H with 224/230 intake and exhaust duration and .515/.520 intake and exhaust lift with a 110 degree lobe separation angle. This will work without the need to change valve springs or go to adjustable rocker arms. The stock ECM will also work fine.

I ran this cam with Gil headers for years

502 MPI cams
 

We have new, billet, gen VI, GM 502 take out cams for $140. They are 115 lobe centers, .226 int/exh duration @ .050 (254 advertised) and 545/540 lift.

We also have them as "100% new / then reground" billet cams comparable to HP500 specs. $200.
They have 115 lobe centers, 232/236 duration @ .050 (258/262 advertised) and 602/612 lift. These can be used with stock roller lifters but there is no room for error on the lifter travel in the lifter retainers. (Dog bones) I would recommend using the longer travel Crane roller lifters just to be safe. (Or at least double check all tollerances) The HP500 cam could also "right on the threshold" of reversion issues if the stock exhaust is retained...

Send me a message if interested.
Thanks, Curtis @ Billet Marine

502 Efi
 

Lots and lots of people have made 502 EFI/MPI's run well. My build included long through transom Stainless Marine pipes, good Crane cam, Crane roller lifters and rockers, pushrods and springs, oversize Inconel exhaust, stainless intake, minor bowl work in heads, reprogram ECU, added RACOR filter after standard Merc fuel filter. My motors were VST and I ran in to a few debris problems with the standard water separator/fuel filter with the VST screen. 450 hrs trouble free so far. Replaced top end components @ 250 hrs. Sounds very nice, idles well, good power. Much less $$$ than a Merc HP500EFI with similar if not equal power.

A very good engine to work with, I believe. And, there are lots around nowadays and good deals are around.