ZL-1 part number question

[William]

I do but am hesitant to do so. The information was requested as part of some legal action concerning aluminum big block engine production. There was another 4-page letter listing probably every aluminum casting/engine assembly they did, even the '0-' blocks and 'BWO' assemblies. No idea what the issue was.

Worthy of note, every aluminum big block casting is not a ZL-1. The earliest doc I have seen is an August, 1967, an order from Chevrolet Engineering to “…provide necessary layout drawings for an aluminum cylinder and case design.” The early castings were dry sump racing engines. The acronym 'ZL-1' first appears in Chevrolet docs February, 1968. Prior to that, it was known internally as the aluminum block L-88. True production ZL-1 blocks/engines are Winters castings #3946052 & #3946053 produced late 1968-August 1969. I just examined a #3946052 block, cast by Lockport in the late ‘70s w/o coolant passages. Not a ZL-1.

The source for much of this was the Gibb paperwork collection, now in the possession of an individual that wants to share it with the hobby in a book. Other people have promised to contribute what they have. As it would contain numerous images of internal Chevrolet docs and engineering information, it is imperative that we first obtain licensing from GM.

I have spoken with them; wheels are turning slowly. They are in the process of re-locating their archives.