N8MAN1068

i have a 350 and 400 block. not sure as to which one to use.
which one has the most potential? can a 400 block use 350 heads?
which one would be an overall best engine?

thanks

jcb999

but... if the question is which makes the most torque.. 400 hands down. Don't go .040" over if you don't have to..

400 motors need steam holes in the heads.. a 350 head will need to be modified.

xxwarrior36xx

HP will be about the same. But if you want more torque, there is no substitution for displacement.

GreenProStreet

Displacement isn't everything in terms of torque. Stroke is the creator of torque so a 383 and 400, or even a 305 and a 350, would be similar in terms of torque. But the bigger bores would give the motors a stronger upper end.

jcb999

That .125" extra bore on the 400 accounts for quite a bit. Your average 383 will make 450-475ft/lbs of torque. A 400 is consistently closer to 500.

The stroke plays more of a factor in where the power band is. The rate that the torque falls off on a motor with a 3.75 inch stroke is much faster than a 350

AlkyIROC

Any head can be used on a 400 block. You just need a 400 head gasket as a template and drill the steam holes into the new head.

Larger bores create more HP. Longer strokes create more torque. Short stroke engines such as the 302 didn't produce a lot of torque but because of the short stroke and large bore they were able to make a lot of HP at very high rpms. That's why a 305 costs so much to make a lot of HP when compared to a similar 350. The bore is very small.

Comparativly speaking the 383 and 400 will have close to the same torque but the 400's larger bore will make more HP. Since HP is a calculation from torque, the 400 will have a higher torque curve while still maintaining the same amount of torque as the 383. If the 383 makes 400 pounds of torque at 3500 rpm, the 400 would make 400 pounds of torque at 3800 rpm (close enough example).

This is assuming the same cam, heads, intake etc are used on both engines.

five7kid

iTrader: (14)

Break out your April 2002 "Chevy High Performance" magazine. Turn to page 75. Read. Understand.

They compared two build-up article engines that produced 500+ HP: a 406 (513 hp @6200, 463 lb-ft @ 4900), and a 355 (527 hp @ 6400, 450 lb-ft @ 5600). Although they didn't actually mount them in a car and make a bunch of passes, they did run the power curves in the Racing Systems Analysis Quarter Pro computer program simulating a 3500# Chevelle.

Results? The 406 got there first, but the 355 was running faster at the end.

Which would you rather be: First? Or faster?

(BTW, bore does influence torque. Torque is force times lever arm {a function of stroke}, force is pressure times area. Bigger area = more force for the same pressure; more force = more torque for the same lever arm.)

GreenProStreet

True, the 400 will create more torque than a 383 everytime, but it you compared the engines on a low to mis range rpm, say...1500 rpm, they would be almost identical. But sayat 5000 rpm, the 400 will make the 50 lb.ft of torque you were saying. If the extra torque generated purely on the displacement, 5-10 lb.ft, peak torque numbers will be the same, while average will be more in favor of the extra cubes.