Yenko block on Ebay.

[bergy]

Just for clarification - are you indicating that the block above is an original "born with" block? When I was at Tonawanda, we produced the cores for the ZL1 blocks in house and shipped them to the aluminum casting facility. It wasn't a difficult task to find a gravity pour, sand cast facility that could pour the castings. The problem was that only the biggest automotive foundries had the Osborne Machines that the water jacket cores were made on. Special sand magazines, ejector systems, unloading fixtures - these expensive equipment investments could not be justified for small production runs. Front & rear housings, along with barrel and fuel pump cores were made in oil sand. So, we made the cores and shipped them out to the aluminum foundry. that "YENKO" feature was added by hand. maching was done on a single CNC machine at the Tonawanda Motor Plant. No broaching.