gen iv engine rebuild

I have a 1989 supra pirata ski boat , i am in a full blown restoration , and i am working on the power plant now , i have experience in the race car industry and i have engine combos that go over 1000 hp for street applications , but i have now entered the the world of water , and the engine that came in this boat feels like a log but is quite smooth , however i want to be able to have a nice cackle to the idle and drive ability as well , here is what i have come up with someone please tell me where i am screwing up at , I have taken a 454 block punched it 60 to make 468 ci , i am using a Keith black forged piston with a mid dome , i got a set of the procomp 320 cc rectangle port heads and the compression is coming in around 10.3to1 , i am using a comp cam xm278 hydraulic cam , the intake i chose was an edelbrock rpm performer duel plane air gap , i am dumping the steel flywheel for an 11lb aluminum flywheel , the crank is forged and the rods are gm 7/16 dot rods with floating pins , everything is to be balanced , can some one enlighten me to the problems i will encounter with such a combo , comp cams tells me i might be a little hard on the trans while engaging it into gear ,of course they make cams , and i would like to hear from people whom build boats , even the bad critisim is welcome this is a learning world

Re: gen iv engine rebuild

at 10.3, your going to detonate. dont think race engine, think tow truck engine. Boats are under constant load, unlike a car. I would back off on the compression ratio a bit, or plan on 91 octane.

and yes, you will be hard on the drive without the heavier flywheel.

Re: gen iv engine rebuild

the flywheel makes since , i am thinking tow motor the peak tq is at 2500 and peak hp is at 5500 , i already run 93 oct gas , what about controlling timing with a timing computer

Re: gen iv engine rebuild

I have a 1989 supra pirata ski boat
and i am working on the power plant now , i have experience in the race car industry and i have engine combos that go over 1000 hp for street applications , but i have now entered the the world of water ,
i am thinking tow motor

Click to expand...

Nope,... yer not thinkin' dumptruck type towin' motor.....
That's what ya gotta get yer head around to build a kick-butt boat motor....
Idle to 5 grand....

'n yer hull is a Ski-boat,... They don't really take to friendly to Big horsepower,....

Put a motor like yer talkin' in front of a Jet-drive, 'n you'll have something....
A motor somewhere in-between the dumptruck motor, 'n yer dream motor, 'n you could run a sterndrive hull...

Re: gen iv engine rebuild

fab9racing said:

I have taken a 454 block punched it 60 to make 468 ci , i am using a Keith black forged piston with a mid dome , i got a set of the procomp 320 cc rectangle port heads and the compression is coming in around 10.3to1 , i am using a comp cam xm278 hydraulic cam , the intake i chose was an edelbrock rpm performer duel plane air gap , i am dumping the steel flywheel for an 11lb aluminum flywheel , the crank is forged and the rods are gm 7/16 dot rods with floating pins , everything is to be balanced

Click to expand...

Compression is a bit high. I would go with flat tops. Try to stay under 9.75:1. It's just more practical with the crap gas you may run across. Large oval port heads would make more torque than the rectangular ports up to 5500rpm with only 468 inches. I doubt you will see more rpms than that. Cam should sound good. The RPM Air Gap is the best dual plane out there. I'd run a 750 DP Holley on that.
Keep the steel flywheel. I've heard of engines dieing when you put them in gear with lighter flywheels. Don't those have like a Borg-Warner hydraulic type tranny? If so it should be no problem to it when putting it in gear. My question is what are you going to do to upgrade the exhaust to compliment these modifications? Do they even make a performance exhaust for these mid engine style boats?