Read my post above, the SY is what it is for a yenko I believe, and the other letters decode to an actual engine number that could be tracked. From the letters on mine, this person I mention above has a book that tracks those blocks that were made. I think he worked at Yenko back in the day. In any case if the owner of the block gets in contact with that person, I am sure we can get an update on how its decoded. I pretty much forgot what I knew as I sold my block a long time ago, but put a ton of time into finding out what I had.

Ruh-roh...

https://images2.imgbox.com/cb/89/LYwtsAIh_o.jpg

So when did Yenko either start or stop having their name cast into the block as shown above?

This is said to be a 69 Block from HBC

Lee, I thought I read that Yenko started doing that in 72 or 74. Something about they aquired the tooling and did the block but add the YENKO where the Winter's crest was. I think they also cast blocks with a Yenko shield like the cars Yenko shield emblem.

Mine looked to have the winters snowflake ground off. It did not look like they ground down an area as large as the yenko letters. So I think the 74 block I had looked like the one with the unfortunate crack.

I wonder if these blocks have a curse. Mine, after I sold it, the guy calls me years later and says it developed a leak, and wondered if I knew about it. I said well, you spent a lot of time inspecting it, I said I got it like it is, all freshly rebuilt by someone else with the best stuff, and it is what it is. I am glad I sold it as it obviously did not hold up.

Aluminum Yenko BBC From the mid 80s, for reference.

I'm curious if the car that HBC is selling has one of the 69 ZL1 engines or it's one of the OTC ones?