I needed some help with a small problem im dealing with, I don't really know much about engines or 3rd gens but im really intrested, my question is...Would a harmonic balancer for a SB 305 V8 fit on a SB 350 V8?

 

Yes it would fit but they are not the same diameter. It should still work but I would look at getting one for a 350.

 

It will fit. Depending on the year the timing mark may be incorrect.

 

Both engines are internally balanced, so the balancers should be interchangable. One thing to understand is that some truck engine and early passenger car balancers are larger than most other balancers (8"). If you have a 6-3/4" (actually measures 6-7/8") balancer, that's what you'll be needing. As long as the balancer is not designed for a 400 SBC, LT1, or L99, it should work.

The other thing to check is the timing mark. Most SBC balancers from the Bronze Age forward had a timing mark that was set about 7° retarded from the crank keyway. These were designed for a timing mark that was installed at the left of the timing cover, at about a "2 o'clock" position. Some later SBCs, possibly your TBI, had a timing mark that was at the "12 o'clock" position (directly under the water pump), and had the timing mark retarded about 45° from the crank keyway. The difference is easily determined by sight.

As you undertake the exchange project, make sure you use both a puller AND an installer tool. Do not use a hammer or the balancer bolt to install the balancer, or you very well may be back in here posting a thread like:

"Help! Balancer bolt and crank threads stripped!"

Remember to clean and lightly grease the timing cover seal and balancer hub before assembly. If you remove the balancer and discover signs of leakage around the timing cover seal, it's a good time to replace the seal. The $4 you'll invest in a seal can help keep the new balancer elastomer from getting oil soaked and rotting out in short order.

 

I wasn't sure if the balance might be a little different since the 1 piece has additional weights on the flywheel due to differences in the crank. In my application I went to a 2 piece rear main and used the 350 balancer (freebie). The 350 balancer was a different diameter.