Hi Guy`s, Chevyman`s Dad again. I`ve just picked up a SB 350 for the 71 malibu to replace the 307.My question is how do I tell if it`s a 383. The guy that had it( before it was stored for 8 months)says its a 383(397010 block)Heads are 3930441 so they appear stock.He had some one build it.I`ve heard it run before it was taken out an it was fine. Don`t know what cam is in it, but I`ve got a comp 268H with new spring an lifters I can put in it.It also has a performer intake on it. an a junk lookin Q-jet.Its got an auto flywheel no weights on it an a BIG harmonic balancer. Havent pulled the pan yet. Motor is very clean in the lifter valley an heads. If this is a stroker motor Jeffrey will probably bust!!! Any help is appreciated. Dad

Usually you can tell by the balancers. The 383 will use a 400 SB balancer.

If it is a 383 then they used the wrong flywheel. They should've used one from a 400 which has counterweights on it.

Originally posted by Jp-15:
Usually you can tell by the balancers. The 383 will use a 400 SB balancer. Originally posted by webfoot:
If it is a 383 then they used the wrong flywheel. They should've used one from a 400 which has counterweights on it. Unless its internally balanced.

Get the crank casting / forging number.

hecked again no flywheel wgts, Balancer is 8" by 1an1/8". If I pull the pan there should be so grinding marks for clearance Right? An where would the numbers be on the crank or balancer? Jeff

If you pull the pan you can measure the stroke...3.48 equals 350...3.75 equals 383