6:71 would work, but 8:71 would heat the charge less and fit just as easily as the 6.

Listening to all this information on the 454's with and w/o the blower, I am curious to know if anyone knows what a stock 454 with 420 hp actually had for hp realistically? How does this compare to the hp numbers of a 502/502 or 454/525?

I had a 365 ( 454 Mag ) that I had a B&M 174, with 5 lbs and a 1050 Dominator with Gil Exhaust and it made just under 500 hp........ DOH

RT

how many hours were on it when you installed the blower and how many more did it last? Tanx

I ran a motor that started out as a 330 and we changed heads to rectangular port GM heads with Inconnel exhaust valves and some port work. The block was bored 30 over and we used J&E blower pistons. I had a B&M 250 with a 850 Holley and a hyd cam shaft. Not sure how much power it made but I ran the crap out of that motor for about 3 years before I installed a 496. With the 330 the boat would run 61 to 62 mph after I installed the 460ci blower motor it ran 82 to 83 mph. After I installed the 496 it was a total terror, the boat would run 94mph and out run most of the hot rod out boards getting there. In my opinion a 10/71 is to much blower for your 454, by that I mean it takes a lot more power to turn a 10/71 vs a 250 or a 256 blower. If I were doing what you are doing I would sell the 10/71s and buy the Blower shops 256. Or build larger motors and use the 10/71's. Add a 1/4 inch of stroke and build a set of 496's

Any idea how much power any of these engines made?

F377,

A 454/HP420 made 420 crank hp. Figure on eating up around 25hp thru the drivetrain and you get somewhere around 395 at the prop.

A 454/525SC made like 525 crank hp. Somewhere around 500 at the prop.

The 502/502Mag carb was 415 crank, 390 prop.

There is no 502/502 (except from GM as an automotive crate motor), but there were 502/HP500 (carb) motors. They were like 470 at the prop.

The 502/500EFI is also like 470 at the prop.

The 502/525EFI is like 500 at the prop.

I built two Ho425 crate motors with 177 blower and 750 holly's . The dyno sheet shows 536 HP at 5300 . This boat has been sold and still running strong 5 years of wide open throttle, The best thing the motors would idle all day long. They were in a 29 fountain and would run 83 on gps at 5300 with 28 hydros spinning in. The ticket would be blowers on the new 525efi.

The 525sc is a 454 with a 177 Weiand blower. Requires 92 octane. I have 2.

I am pulling the 454 mag in the Baja and replacing it with a 525sc next week. Here it is...it looks just like yours OkieTunnel.