Posted by Brian in Oregon on January 05, 2000 at 20:06:32:
In Reply to: internal/external balancing posted by sal rossi on January 05, 2000 at 14:16:26:
An internally balanced engine had whatever weights are needed to balance the crank, rods, pistons, flywheel and harmonic balancer inside the block. This can be as simple as removing metal from a crank counterweight to an added offset weight that fits the crank snout. The flywheel or flexplate and harmonic balancer are neutral - that is, they are in perfect balance.
An externally balanced engine means whatever weights are needed to balance the recipricating assembly are in the flywheel or flexplate and perhaps the harmonic balancer.
I'm not that familiar with Mopars, but the Ford 390 and 427 engines are internally balanced, and the 428 series is externally balanced. Even though parts will physically swap, they won't be in balance. Example - you cannot put a 428 flywheel on a 427 unless you removed the offset weight and neutral balance it. A lot of folks get in trouble when they start backyarding parts between internal and external balanced engines that share common bolt patterns, etc.