FIXX

iTrader: (2)

4.600 bore and 6.700 rods..632..

Dean Ferry

I'm happy with my Victory marine 572, 680 hp BBC

GPM

That's a short piston

Black Baja

iTrader: (2)

It is short. That's what's in my motor. It does have some rock and with the piston at tdc on a zero deck it's a little nerve racking how much it will rock out of the bore but its a good combination. I've ran it wide open with out even touching the throttle and used 30 gallons of fuel... I'm going to tear it down in a couple weeks and see how hard the big stroke really is on the motor. Not many guys have done this in a boat so there really isn't much info on the combination out there.

As far as the OP goes as said b4 the 320 head isn't a very good head and leaves alot on the table. If you use that had on a big bore motor and need a dome piston to get some compression I you will probably run into more trouble. You can order heads with the chamber for the bore size and ill bet the head is for a 454. If you use a 4.500 bore dome piston the dome will probably have to be machined. Just some things to watch out for. Mistakes I've made in the past...

ezstriper

the 632's have a issue breaking cranks around here in race app's we have good luck with short deck 565's but the tall 572's would be my choice in tall...

bcfountain

I am guessing too the 565 would be a reliable setup.maybe alittle cheaper to build.ezstriper do you ever boat on lake anna?

ThisIsLivin

How come I never hear of anyone building a 588, 4.560x4.5 tall deck? with the 4.560 bore the cylinders walls still have some beef and can be easily rebuilt. Going to a 4.600 bore in a marine motor is too close to the edge for me. I am putting together my wish list for my next boat and this is what I came up with as best combination of power and endurance. I'm still not sure what heads to go with, after looking at the numbers and graphing them out to evaluate area under the flow curve, the AFR 315's look to be the best. I know everyone would go with a bigger head for that size motor, but when you graph out the flow curves for all the major heads, the bigger heads only flow more after .600 lift. I plan on going with a hydraulic roller cam under .700 as most do, so why go with a low velocity port that doesn't flow as well through most of the range of my cam?

ezstriper

Not really...been down a few times but we stay on the potomac..Rob

jspeeddemon

I have a pair of 632's Big block Chevy's in a twin-engine Daytona for the last two years, to this point I have not had any issues with either one of them. They make about 850 hp piece, and really considering everything don't use an extreme amount of fuel! A friend of mine has a twin-engine Donzi with a pair of 588 big block Chevy's that make about 800 hp piece, and is really a better combination considering piston pin heighth and wear issue on the cylinder walls, considering only the 50 or 60 horsepower difference

Black Baja

iTrader: (2)

Yes but it would really suck if you had the 588's and needed the 632's and the xtra hp... I went from a 598 to a 632 and what a difference it made in running attitude of the boat. With all the xtra torque the boat really sits back on the drive. With the 598 the boat always chine walked 632 its very rare usually on dead flat water...