Harmonic Balancer Code question(s)

[Joseph W.]

Re: Harmonic Balancer Code question(s)

One more thing to add to the list!
thank you for the explanation

[Joe L.]

Re: Harmonic Balancer Code question(s)

Hi Joe:

Regarding your statement that the 3947712 and 6272224 are identical and cannot be told apart, I think there is an interesting difference between the early SHP balancers and the later ones. It appears that this change first appeared on the 6272224 and may be present on every service replacement that came after the 6272224.

The first photo below shows this difference. The second photo, which is from an ebay listing, shows the same feature appearing on the currently available service replacement 19260269.

Up until the 6272224, the SHP balancers had an inertia ring that was approximately 1.71" wide and was mounted on a hub that was also about 1.71" wide.

On the sample 6272224 that I have, the width of the inertia ring has been reduced to 1.61" except for a small "collar" near the hub. This collar is approximately .125" high. The hub casting is the same 3942538 that was used in the full-width, non-finned balancers that preceded the 6272224.

Do you have any idea why this change was made for the 1972 LT-1? I suspect that GM altered the design to gain a bit more clearance between the back of the intertia ring and some other part that may have been new for the 1972 LT-1.

Joe-------


Somehow or another I had never noticed that difference. I even have an NOS GM #6272224 [not for sale] but I don't need to dig it out because I'm quite satisfied with your photos of the 6272224 and 3947712.

I even discovered a "corollary" part configuration: just as the 3947712 was replaced in July, 1972 by the 6272224, the GM #3947704 was discontinued in July, 1972 and replaced by the GM #6272222. The 3947704 was used on 1969-71 Corvettes with 300 and 270 HP engines. It is an 8" balancer but of 1-5/8" outer ring width. I have both the 3947704 and the 6272222 and I always thought they were identical. However, sure enough, the 6272222 has the slightly extended balancer hub as you've depicted.