Thanks Dennis, headwork won't do any good? I take it they flow good enough until you get into higher hp and higher rpm?

What about a more aggressive cam with springs and adjustable rockers and reprogramming the ECM?

If you are going to reprogram the ECM then you should improve the exhaust and install a roller camshaft. Contact Arizona Speed and Marine and ask them what camshaft and exhaust they recommend for their computer upgrade. They can set you up with a complete matching ECM, camshaft and exhaust system.
Sincerely
Dennis Moore

Well, I guess that answers my question. Not much to be gained unless you really want to get the wallet out and go for it!

Okay BUDAH, here's a question foy you, if I did decide to whipple it how much rpm would I gain keeping the drive stock? I have heard that you can add a little pitch to blackhawk props but I have no idea if it's true. My boat only runs 4600 rpms trimmed where it rides the best. I have been doing the math and IF I could add 2" to my pitch and run at 5200 rpm that would give me about a 15 mph increase.

Tyle Crockett Marine has a system for the 502's that will take them to around 500 to 525 hp. It consists of reworking the heads, new cam shaft, roller rockers, honing the intake, re-programming the ecu, and a few other things I can't think of. All the parts cost around $2,000, and you would probably have $1,500 to $2,000 in someone installing it all.

Dennis Moore,

Wouldn't that cam--Comp Cams Xtreme Energy XE 268H - with a 110 LSA be causing reversion problems? Especially with stock exhaust.

Does anyone actually know someone who has run that Tyler Crocket system and can tell us of any success with it? I am always skeptical when it comes to engine builders who make statements regarding engine upgrades, especially when it comes to EFI. In my opinion, the only way to get an ecu re-mapped correctly is on a dyno.

They had a article in Hot Boat magazine about, I can't remember exaclty which month and year, but if I remember correctly they did put it on a dyno to get the actual results

I remember some of the mods in the article that Tyler Crocket did for Hot Boat Magazine. He took a stock 502MPI and added larger valves, different hydraulic roller cam profile, roller rocker arms, cut the heads .020", added larger 2.25" intake valves, reprogramed the ECU, and added CMI headers. I am pretty sure they didn't mention anything about PORTING of the heads---they probably just cleaned up radius's a little and I do NOT remember if they extrude honed the intake or not---i don't think they did, but they also put on a better air filter like a K&N or something. They ran it on the dyno and it made about another 100hp.

Pulling the engine(s), tearing them down, adding the parts and doing the mods---- especially the headers will cost probably close to about $5K per engine or better. The headers make it expensive (roughly $2,500 per set). Unless you want to keep it naturally aspirated, you could put a Whipple on it and you'd still make more power for about the same price. Lot's good input here from the others, but it is ultimately your decision of course. Hope all goes well whatever way you decide to go

Checkmate
Not really, water ingestion is a product of the intake and exhaust valves being open at the same time, called overlap. A relatively mild camshaft, with a moderate amount of duration, won't have a lot of overlap. A tight lobe centerline doesn't have much to do with overlap. Two degrees of additional overlap is all you will have between 110 and 112 LSA. An increase in overlap is much greater when you increase valve duration by 8 to 10 degrees on both the intake and exhaust lobes. Water ingestion from overlap doesn't really start effecting most big block marine engines until you get above 230 degrees intake and exhaust duration. Then you need a wider LSA. I believe a smaller duration cam with a tighter LSA will make more power than a larger duration camshaft with a wider LSA.
One last thing, intake manifold vacuum pulls the water into the cylinder through the open exhaust valve. A dual plane intake manifold will give the engine more vacuum than a single plane intake manifold. More water ingestion with a dual plane!
Dennis Moore

Head work WILL make more power. It depends on who does the work.

Dennis

I will supply the head work, your dyno.

I have a 500EFI system for sale