Bore & Stroke?

[DavidNJ]

My question is not why 482 and not 427. It is why 427 and not 496? Or 525?

The 4.31 bore is as well supported (rings) as the the 4.25. It seems like it would be the same cost. Why give up 14 cubes?

Now the 525 is 4.31x4.5. The only problem is there aren't any inexpensive 4.5 cranks.

JE lists 4.25, 4.28 and 4.31 pistons for the 4.25 stroke/6.7 rod combination. Diamond doesn't list the 4.31 in the catalog. However, as Barry said, they have it available.

[Streetwize]

The only thing overstressed about my 427 smallblock is MY NECK after driving it Proper machining is a must square decking, line honing, deck plate hone goes a long way on any motor.

BTW: A 283 chevy isn't anything close to square 3 7/8" bore 3" stroke, it would have to be 3.56" bore & stroke to be square.

A 327 is 4" by 3.25

The bigger bore than stroke was much more important years ago before modern cylinder head and combustion chamber designs evened the playing field. Rotaing mass (bobweight) has a lot more to do with how fast a motor will rev than bore and stroke alone. A 4.04" x 4.17" 427 smallblock with equal flowing heads, cam timing and compression will still rev quicker than an FE unless you have (for example) a knifedged lightened crank and aluminum rods to even up the mass. And not only the bottom end, valvetrian mass also has a considerable effect and again, advantage smallblock.

Most 4 cylinder 4 valve motors often/usually have much larger strokes than bores and some of them rev to 8500 or more easily. A mitsubishi 4g63 motor is a good example, early first gen (89-92) blocks have 1.6:1 rod ratio rods and routinely take 9000rpm and 24psi of boost and make over 350 streetable horsepower, to put that into perspective, a 427 would need to produce 1225 hp to equal that HP/Cube.

[Commander]

Originally Posted by Streetwize

Most 4 cylinder 4 valve motors often/usually have much larger strokes than bores and some of them rev to 8500 or more easily. A mitsubishi 4g63 motor is a good example, early first gen (89-92) blocks have 1.6:1 rod ratio rods and routinely take 9000rpm and 24psi of boost and make over 350 streetable horsepower, to put that into perspective, a 427 would need to produce 1225 hp to equal that HP/Cube.

Link

Your math is pretty close. I'm assuming the 24psi of boost was coming from a turbo? The FE above was dyno'd at 1,030. To drive the blower is probably over a 100HP, so call it 1,130 HP. And the owner was still working on the tune. I don't think he needed to go over 5,000 rpm to do those numbers either. I understand he's working on a twin-turbo FE hemi SOHC next.

9,000 rpm why? just to get 350 HP? a big block can make 350 HP right out of a clapped out 1967 LTD with a little freshening. You got to know what to spend your time on/with.

[Streetwize]

Originally Posted by Commander

Link

Your math is pretty close. I'm assuming the 24psi of boost was coming from a turbo? The FE above was dyno'd at 1,030. To drive the blower is probably over a 100HP, so call it 1,130 HP. And the owner was still working on the tune. I don't think he needed to go over 5,000 rpm to do those numbers either. I understand he's working on a twin-turbo FE hemi SOHC next.

9,000 rpm why? just to get 350 HP? a big block can make 350 HP right out of a clapped out 1967 LTD with a little freshening. You got to know what to spend your time on/with.

Well 350hp is at about 7400, it'll rev to 8800-9000. In addition to my Cobra I have one of these little pocket-rockets, and with the help of AWD and a 4800rpm rev limiter (for clutch dump launching on 6psi of boost) it's showed it's tail to quite an array of high dollar Fast cars. It's a total sleeper. There are many 1st get mitsus running upwards of 550hp on stock blocks and cranks, they were very well engineered little motors.