I pulled the 305 out of my 86 IROC and built a 383. I have placed the 305 Balancer on the new engine. Is this a mistake? I have read that it fits, but is it right, or will a new balance be better for the longer strock engine?

 

Is the 383 crank internally balanced? If not, the 305 damper doesn't work no way no how.

If the 383 crank is internally balanced, using the 305 damper is penny wise and pound foolish. Get a new damper, they don't cost that much.

 

yes mistake, the 400 crank is external and a 2 pice rear 305 is internal so you can't use it unless it's converted to internal and most aren't so find that out first and just buy a new one

 

While all 400 cranks are externally balanced, many aftermarket 383 cranks, especially one-piece rear main seal cranks, are internally balanced and take standard '86-up damper and flexplate/flywheel. That's why I asked it if was internal or external.

 

Thanks I will order a new one tonight!!

 

What did you order, internal or external?

 

Neither, but the engine is internally balanced, I could not find a balancer for a 383. I don't mind spending the $, but the balance that is on the car, is in good spape, so now I am questioning the reason to buy a new one. And what size do I get?

 

If your crank is internally balanced, you get a damper for a 350.

The size and the timing tab are directly linked. If you are using the timing tab attached to the front cover, you need to get a damper to match it. Most aftermarket dampers use the "0" mark at the 2 o'clock (approximately - vs. 12 o'clock) position, so keep that in mind.

Larger dampers tend to work better than the small ones. They don't contribute significantly to rotating inertia, so don't get a small one thinking your engine will rev up quicker. The beneficial effects of the large damper off-set any inertial mass, so keep that in mind.

Ditto that with regard to reusing your old damper. They do get old and lose their effectiveness, a new one is good insurance.

If you don't spin the engine above 6500 RPMs, you don't need an SFI damper.