Crank shaft pulley
 

I have a GM stamped 3921923BM pulley SINGLE GROVE !!!!!!! I looked up the parts number and it says double grove ?????? any ideas Thanks Joe

Service replacement parts are often not the same as OE.

I believe the notation means the service 3921923 pulley will have 2 grooves but function as original for manual and power steering.

Joe's photos here, FYI:

https://www.yenko.net/forum/showthre...hlight=3921923

I'm not sure either...
Anthony

Sorry guys didn’t remember I posted it 3 years ago !!!!!!!! Another GM part out of the Jenkins Competition archives. There has been quite a few of them. !!!!!!!!