called Damperdudes and they got me squared away! Thanks Ron for link!

 

I still have a lot to learn and little time to learn it, What did DamperDudes say about your balancer / damper? Also did they confirm the application for your engine. I need to be corrected if I was wrong.
Ron

 

Well…it appears not to be a 3817173, but rather a service replacement for an LT1 block post late 60’s. It would still work in a 365hp build but the NOS timing chain cover I have would not work because of the CCW 10 degree offset. Damperdudes hooked me up with the correct version and took the time to explain the difference between the two balancers. So I will live and lean on this! The NOS box and pics shown to me prior to purchase were either purposely deceptive or the seller didn’t realize himself that the balancer in the box was not what he thought it was! Either way, in the future I will double/triple check before I buy! One thing I did lean is that many of the service replacements look the same across different part numbers and that alone can be confusing, at least to a novice like me. A final shout out to Ron at Damperdudes, he took the time to call me and spent considerable time going over the options. I would definitely recommend them to anyone looking for a balancer!

 

Thanks for the update, that helps all of us here on the forum. Sometimes things aren't quite what they seem.

 

A few years ago I researched the evolution of the 8" balancer used on 1960s Corvettes and then offered by GM as service replacements. There were two big production changes in these balancers during the 1960s:

1) The "fins" in the back side of the hub on the 387173 balancer disappeared during the 1967 production year, but the part number did not change.

2) Starting in 1969, the timing mark was moved by about eight degrees. This required a different timing chain cover to match the new location of the mark. The pre-1969 timing mark was ALMOST aligned with the keyway groove.

Following is the evolution that I compiled for the 8" balancers:

GM SHP BALANCERS THAT ARE 8” DIAMETER BY APPROXIMATELY 1.71” WIDE

3817173 C2 balancer has hub casting 3796769 (finned style) or 3942538 (non-finned style)

3947712 LT1 balancer (hub casting 3942538)

3947708 Z28 balancer (hub casting 3942538)



GM SHP BALANCERS THAT ARE 8” DIAMETER BY APPROXIMATELY 1.61” WIDE:

6272224 1972 LT1 (hub casting 3942538, with inertia ring reduced to 1.61” wide)

12551947 (GM service)

12555879 (GM service, has degree marks)

88960604 (GM service,has degree marks)

19260269 (GM service, has degree marks)

Based on the screenshot below, I think you have the 12555879 balancer. I'm surprised that the last four digits of the part number are not stamped somewhere on the machined surface of the balancer. Note that this would normally be a stamped number added after the balancer was assembled. This is different from the cast-in casting number or cast-in casting date for the hub.

It's unfortunate that you received an LT1 balancer in a box marked with a C2 balancer part number, but it's good that you caught the problem before you installed the balancer. You would have had a hard time figuring out why the timing seemed to be off several degrees.

In fairness, the seller may not have even known this was not the part that originally came in the box. People typically assume that the part found inside an open box is the part that was originally in that box, but that is not always the case. I recently saw a reputable ebay seller offering a "NOS" C2 gas lid, along with the correct GM open box, that was clearly a Trim Parts reproduction lid. He probably acquired the lid in an open box and simply assumed the lid in the box was the lid that originally came in that box.

 

Great info and thanks for the reply! A really neat part with owning any classic car is the journey after purchase!