I always rec. this one but it works well in the 454 with smaller Vortec heads and 9.1/1 compression. The ZZ502 cam from GM.Forget the exacts but about 224/234 dur and 527/544 lift. Plenty of cam for up to 5500 rpm and very strong torque down low. You could prob go bigger with a good non reversion exhaust but it will put you around 500HP tons of torque and it's cheap from GM $160 or so.
I'm also in love with the Dart intake I'm using although it's a little big it does plenty from the get-go without bogging,,would be even better on your. Mine is for big oval ports but rec is the most common,,Ebay $250,,,looks like an HP500 to I have used Edelbrck torquer II's on other boats and they did well but because of flat tappet cam and sim spec it was weak on the low end compared to the roller set up.
Don't mind Mcollinstn,he can't help himself but after he vents he usually has some very technical and helpful info,,usually.
I am no expert but have built about 6 boat motors over the years and am learning here.

doug, ive got that zz502 cam for you....!!!!.......also know that guy still has his hp500 intakes!!

just a reminder!

anyone looking for gen 6, zz502 cam, gm lifters, dog bones, spider, timing chain and cover.....ive got all new take offs i want to get rid of reasonable!!!

sorry to use your thread for my ad doug!!! ill be quiet now

I would have thought the Crane 731 or 741 would have been great suggestions. Is that wrong?

Might as well use it for something good Kevin....

RLW thanks again..

Rmbuilder Rest up and call me when you're feeling better.

No, there's no wrong answer, I'm just looking for people's suggestions on what to run from their own experiences, as I don't have a lot of experience with marine engines. All the engines I work on have about 16:1 compression and run 25-30 psi turbo boost!!!


Later,

Doug

all very good i would try to boost compression to about 9.5 but no moor than 10.2 the hyd. roller cam 830 to 850 4150 hollie, dart typ intake.. i have a ,, iam told a crain cam from hp. 500 and 32 value springs to to mach. springs have about 15mins time. 2 110 mech fuel pumps..913 9477222.. ps dicth the water surculationg pump, for 15 moor hp eeeeees

50boat, I doubt that you'll find 15 HP by removing the "surculationg pump" and think in our colder water temperatures it should be left on. Doug, it looks like you're dropping the EFI route in favor of a carb. I think it'll make life much easier in the search for more horsepower! Maybe you should start another thread under a different screen name. It seems alot of people want to rag on you instead of helping! Steve

With the E/I ratio you will be looking at something in the high 220 range on the intake and around 12 degrees more on the exhaust. Lift, will be around 630ish on intake an high 500's on the exhaust. Max rpm will play a factor and without it these are just speculative. The 500HP reliable will be no problem.

Chris

Hey Cooltoys,
You are describing an engine that I had planned to build this winter but I got a great deal on a 502MPI instead.
I do still plan to build up my 1999 7.4MPI at some point too...
My plan is for 454 with flat tops, vortec heads, dart intake, 750cfm carb, ZZ502 cam. Hoping for 420HP+ at 5200rpm...

After several phone conversations with RMBUILDER(MarineKinetics)
, I ended up having Bob spec my camshaft.

When I asked about intakes we ended up having an hour long discussion and when I hung up the phone I realized he had never given me a "brand name" of what to buy, but instead educated me more on how to decide for myself

and as you can see by the results a well engineered combination pays off




Here are the rest of the specs

Engine build and dyno results


Doug