My 71 Stage 1 heads have this marking stamped on the end boss- reads BPE 3492A (the other head is B). I assume this is a machine shop or head porter that worked on these in the past.. anybody familiar who this is (or was)?
My ported 70 stage one heads have HRE 673 stamped on them. I believe I read somewhere on here before that was one of the companies Kenne bell used for porting.
So I called them and that is their stamp. and of course their records dont go back that far but the work would have been done about 1992 or so. They did do a ton of work for Kenne Bell at the time, and interestingly not just head porting, he said a big part of the work was standard conversion of small valve heads to Stage 1's.
