1968 Crank Pulleys. Are they? If not, what are t

[John Melvin]

Heres is the deal

1. Just took the what I beleive is the original crank pulley of my 1968 L-36. (Non air, Non PS/PB)
The crank pulley is stamped steel, has a number of 3921923BM: What year/is this correct?

2. I ordered a crank pulley from GM resto parts: its a rough cast iron pulley. It has the number 38996 then 60 BM, then what looks like a casting date on it of 24697 (or 24G97). It doesnt have a solid face like the one I took off. Its heavy, about a inch smaller in diameter, has three "spokes" (instead of a solid face), and the belt grooves are much deeper than the one I removed. It also has what looks like "drill dimples" on the face one on side to balance the puley. What is this pulley for? It fits right on my crank like it belongs there

[John Melvin]

Re: 1968 Crank Pulleys. Are they? If not, what are

If this helps, this is the second pulley in question form GM perf parts
https://www.spoperformanceparts.com/

[Joe L.]

Re: 1968 Crank Pulleys. Are they? If not, what are

John-----

The GM #3921923 stamped steel pulley is likely the original pulley for your 68 L-36. The 3921923 was first used for 1968 Corvette big block applications, primarily L-36 and L-68, although it was used on others, too.

The cast iron GM #3863108 was used on all 65-67 Corvette big blocks and also many 68 to 71 with SHP or HD big blocks. It is functionally interchangeable with the 3921923.