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RJ, Could you please expand a touch about the bolt info. I went to bed last night thinking about the TR balancer bolt with the hole and realized that I gave the wrong answer. THen MH emailed me and said I was wrong also. I said that the low HP Corvettes had a TR balancer bolt with no hole. Well they didn't have a bolt at all holding the balancer onto the crank.
Is this how it goes??? Corvette Flint engines with hi-hp used the TR balancer bolt-with the hole and the Chevy Engines did not used a TR bolt without the hole???
I know for a fact that an all original 340 Hp 63 had the TR w/wire hole. I recently got a correct balancer pulley for a 63 that came from that 340 engine. It has the original bolt (had).
Please educate all of us on this rare bolt. NM's next to subject doesn't cut it Sr. What is the finish of this bolt? Blackened?
What is the finish of the three pulley to balancer bolts-zincad? Thanks, JD
The bolt pictured is a GM #9428643. It was used for most, if not all, small block balancer bolt applications from 1969 onward. As far as headmarkings go, I'm sure they varied. I would expect that TR was a common one for the 70's. I really wouldn't expect that these things would be too rare. As you can see, this bolt was black-oxide finished, GM 300M material (SAE grade , and had no safety wire hole. It was never available in SERVICE from GM.
The GM #3815933 bolt was used for 1963-68 small block applications originally using a balancer bolt. These included L-76, L-79, and L-84. Other 63-68 small blocks used no balancer bolt, at all. This bolt is also GM 300-M material, but is zinc or cadmium plated and has the safety wire hole. It is still available from GM, although I'm sure the headmarking is no longer "TR". I believe that it will work for any small block application originally using a balancer bolt, although GM never cataloged it for 1969 and later applications.
I posted this photo a couple days ago in another thread (there are about three current threads on this topic). This is a service replacement that I bought in about 1975.
From your description it sounds like this bolt would be correct for 63-68 small blocks that used a balancer bolt. Is that true?
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