Harmonic balancer

[Jim T.]

Still have from date of purchase in 1969 a harmonic balancer for my 64 Corvette 327/300 4/speed.
I purchased the new balancer from the machine shop that balanced my engine parts in San Diego, CA when I rebuilt the engine.
This balancer required force to install, but came off a very short time later while driving. The Chevrolet dealership in Coronado,CA installed a new balancer that did not come off. Said the one I installed was the wrong one.

On the rubber this balancer has HT-1433 ABS9 imprinted.

One spoke of the balancer has " 3 bolt hole 8" stamping.

Another spoke of the balancer has bolt hole partial number followed by 9 stamping. Turning this the number could be 62.

The front of the balancer has 6904H and is 6 inches in diameter.

Any information appreciated.

[Joe L.]

Re: Harmonic balancer

Still have from date of purchase in 1969 a harmonic balancer for my 64 Corvette 327/300 4/speed.
I purchased the new balancer from the machine shop that balanced my engine parts in San Diego, CA when I rebuilt the engine.
This balancer required force to install, but came off a very short time later while driving. The Chevrolet dealership in Coronado,CA installed a new balancer that did not come off. Said the one I installed was the wrong one.

On the rubber this balancer has HT-1433 ABS9 imprinted.

One spoke of the balancer has " 3 bolt hole 8" stamping.

Another spoke of the balancer has bolt hole partial number followed by 9 stamping. Turning this the number could be 62.

The front of the balancer has 6904H and is 6 inches in diameter.

Any information appreciated.

Jim-----

The only number that's really important here is the "6904H". That's a derivative of the complete GM part number of 3896904. That part number is the correct SERVICE balancer for a 1964 L-75 and it has been since June, 1971. The strange thing is that you would have been sold that balancer in 1969. While it was available in 1969, the balancer being sold in SERVICE and cataloged for the 1964 L-75 application at that time was GM #3861970. Incidentally, the original balancer for the application was GM #3817684 which is configured differently than the 3896904 and the 3861970.

If the one you have is the one that was originally installed and came off, I don't know why. It appears to be the correct part number based on the stamping. Perhaps, it was defective and had too little interference fit.

[Jim T.]

Re: Harmonic balancer

Thanks for the identification of my balancer. Until about 25 or so years ago I had it in the GM box given to me as a removed part. The box was what the newly installed harmonic balancer came in by the Chevrolet dealership. When I spoke to the mechanic he handed me the one I installed in the new balancer's box and told me it was the wrong one for my 64 Corvette. Seeing the part number 3861970 jogs my memory a bit, I think that was the part number on the new balancers box which deterorated so much I discarded it many years ago.
Drove the 64 that summer from the west coast to east coast and half way back west in 1969 and had no problems.