blue thunder

Crazyhorse.. looks like my combo may end up close to waterfoul's, less the .060 oversized pistons. Any idea what he is getting for hp? I'm hoping to get 425hp with edelbrock rect port heads and intakes, comp cam 226/236, 544/547 and matching springs, 8.6:1 compression running qjet at 5100rpm WOT. Can't afford exhaust for the twins and do engines too, so will have to live with stock exhaust till I have the jingle. How do you think this will work?

BT

BGIII

blue thunder, your setup is very close to mine except I used an ultradyne 288/296 adv., 231/239 @ .050 cam .550/.575 on 112LSA, lightning headers, and GM rectangle port heads. I used q-jet carb w/ GM/Merc dual plane intake. I think you will be very happy with the setup. My boat gained consistent 5 mph versus original stock 454 mag.

blue thunder

BGIII... did you do engine upgrades and exhaust at the same time? Is it a single engine application? I lost about 3-5mph going from 454 magnums to 330s, so hopefully I get that back plus another 3-5mph. My goal is 75mph, I was at 70-71 with mags, now I am 66-68mph or so (guesstimating). The boat is a 1988 scarab panther (30').


BT

BGIII

Single engine application. All changes made at the same time.

I would love to see results of an engine built this way w/ stock exhaust and then w/ headers. A lot of different opinions, I would like to see some proof whether it's the engine work, the headers, or the combination of the two that makes these slightly warmed engines work so well. the damn headers cost almost as much as the engine.

I will say that the lightning headers made my boat sound like I was one of the big boys.

blue thunder

BGIII, I think the real benefit (other than sound) comes in when you start trying to make high hp, with radical cam grinds. I'm going to go as far as I can without excessive reversion. I don't think exhaust would help much with the selections I am making, but of course those selctions are being driven by the fact I'm running stock exhaust. I can just never go any further without upgrading exhaust. That is how I view it.

BT

BGIII

On the other hand, if you go farther w/ camshaft, you will have to sell the boat w/ 3,000+ dollars of exhaust and not get a dime for it. At least now, you can remove aftermarket exhaust and sell boat w/ stock setup. (assuming you eventually add exhaust)

Crazyhorse

I can under stand why some people would like to do their own cylinder head modifications but believe me when I say a pro is going to do a more consistent job than most of us would. The simple fact is we do a great (but lengthy) job on the first chamber and every one after that gets less attention to detail. BGIII can tell you how much his head work cost. My brain is too full of meaningless crud to remember something useful like that. But hey, being a doper in your younger days can do that to ya.
I would expect Waterfoul's and BGIII's engines to make around 430 to 450 on a dyno. If you guys plan on really beating the snot out of your upgraded engines buy the forged pistons But above all, you need to have a competent machinist to do the machine work, and the assembly process has to be CLEAN, CLEAN, CLEAN.

BGIII

I had the following work done to my rectangle port heads (one pair):

valve job, install bronze guides, resurface heads, machine for seals, magnaflux heads, bake & blast, set spring height, port match heads & intake, slight porting in the intake throats, assembly

The bill for my heads was about $550

Crazyhorse

Yo, Bill. You find another hole in the water into which you'll need to sink cubic dollars?

daveg

I have a 454 300 HP motor and I was also wondering if it would be better to buy because it wouldn't cost that much more and I would still have mine as a spare (you never know). The price is right for the HO454 crate motor but GM says they are NOT for marine use. What's the difference?