For the heavier B body in a cruiser car or lightly hot rodded, a 360 every time. The 340 is a looser in this case due to lack of torque.The 360 will make more torque and peak earlier in HP and very very near what a 340 makes.
Shorter stroke engines are always better at making HP. It is the lack of torque that they suck at no matter what company it is. This is where the longer stroke of the 360 is really nice. Since your rebuilding the engine, the piston prices are equal or a slight cheaper in many cases. The 4.00 bore is more popular across the big 3 company's. .04 in bore size is really very close to zip in HP. But .27 in stroke will show up on the butt dyno, the worst to be able to measure any power there is.
340 is a better design - short stroke/big bore. I'd rather have the better breathing capacity. Hell all you need is a 340 block, and '72 or earlier 318 crank (steel & same stroke as a 340) buy aftermaket heads and make some serious HP.
LOL, are you serious, what Cranky said below.
Better design? Block is the same except the 340 has .040 more bore. Yeah, the early 340's had a steel crank but how many of Mom's cast cranks have you seen broken? Mains are bigger in a 360 tho...and if you want to play games, you can buy a longer rod for the longer stroke and end up with a better rod ratio in the 60. I've seen just as many hard running 360's as I have 340's....
Any engine can be made to go fast, it is just a matter of cubic dollars.
How the heck is a 340's capacity to breath better than a 360? If ANYTHING, it is worse in a 340 at low RPM. At high RPM, (Where this is, is debatable. But we'll in general, call it racing RPM) the 340 is better. A light car should be used. Most B body cars are exempt from this in the street.
I wonder what kind of "Serious HP" you think he'll make with that basic recipe? I have seen cast crank run real well, hold over 550 hp and torque while lasting a long time measured over years.
If such is the case you'll make that the forged crank is stronger and worth to use it in a rebuild and follow your recipe, I want to know what heads your recommending him to use for over 550 HP? W9's?
