Msd pro billet in a small block 360 backfire at idle

The MSD bushings are OK. Never seen them be seriously out of spec. You will get some stacking tolerance issues. I chuckled about a scolding regarding the CNC tolerance, being +- .001 and the amount of change in advance. It is so small you couldn't see it on a manual timing light. We are talking on a 10* bushing something on the delta of .05ish degrees... REALLY... that's not going to be significant or an issue on anything that runs on pump gas.

I used to make these with a hillbilly lathe. A vise, flat file held in vise, drill with mandrel holding a bushing. Then grab the Very Near calipers and spin that puppy out. LOL

Black was the largest diameter and was 18* red smallest diameter at 28* with 4-5 in between those two, wanna say 25-23-21-19.