ZL-1 blocks

[EZ Nova]

I PM'ed 427 KING but got no reply. So I'm asking here.

What are the different ZL-1 blocks that were produced back in the late '60 and early 70's? I've heard there's a difference between the "052" and "052 with the small 2". there were Reynolds Can am blocks, and I hear of "053" blocks????

Just looking for the low down and info on what these actually are, and what the differences are between the different casting numbers.

Thanks, John

[William]

If there is a difference I have never heard what it was. Some of the earliest production ZL1 Camaros have the '053' casting.

Chevrolet produced a few varieties of aluminum big-block castings back in the day. The earliest [1967] were race parts only, provided to Jim Hall/Chaparral Cars for Can-Am racing. For 1968 McLaren was included. These blocks were significantly different from later production blocks, probably had 0- casting numbers. At this time the term 'ZL1' did not exist. When Chevy decided to offer an aluminum block option for the L-88 Corvette it was assigned option code ZL1. It only applies to castings 3946052 & 053. The latest true ZL1 block castings were produced July-August 1969. Later [1971-1972] Chevy did another aluminum bb casting exclusively for racing.

Be aware that in the late '80s Chevy ran off a number of 3946052/3 castings on the original tooling. They used a different, much darker alloy that does not match the older heads. Some of these blocks are around, machined and raw castings.

http://www.camaros.org/copo.shtml

[EZ Nova]

Thanks William. I didn't know of there 80's version of the 052/053 blocks. 052 are what I'm mostly looking for info on. And what does the smaller "2" indicate?

Thank you

[William]

No differences noted in any of the original 052/053 blocks.

[iluv69s]

Just to add to what William has said. Some of the blocks had screw in freeze plugs and some had push in. My original block from ZL-1 34 had screw-in.(and it seems the original production blocks Ive seen are the same). I had an ML code corvette application block that also had screw-in.
Ive had about a dozen ZL-1 blocks (mostly non-production) and Ive seen both ways. Does not seem to be much rhyme or reason.

[COPO_Anders]

If there is a difference I have never heard what it was. Some of the earliest production ZL1 Camaros have the '053' casting.

Chevrolet produced a few varieties of aluminum big-block castings back in the day. The earliest [1967] were race parts only, provided to Jim Hall/Chaparral Cars for Can-Am racing. For 1968 McLaren was included. These blocks were significantly different from later production blocks, probably had 0- casting numbers. At this time the term 'ZL1' did not exist. When Chevy decided to offer an aluminum block option for the L-88 Corvette it was assigned option code ZL1. It only applies to castings 3946052 & 053. The latest true ZL1 block castings were produced July-August 1969. Later [1971-1972] Chevy did another aluminum bb casting exclusively for racing.

Be aware that in the late '80s Chevy ran off a number of 3946052/3 castings on the original tooling. They used a different, much darker alloy that does not match the older heads. Some of these blocks are around, machined and raw castings.

http://www.camaros.org/copo.shtml

I´m a bit confused about the blocks being produced in the 80`s, since Yenko got the rights to the blocks in 1976 and changed the tooling to reinforce the blocks. So what did happen back then ?

[William]

I´m a bit confused about the blocks being produced in the 80`s, since Yenko got the rights to the blocks in 1976 and changed the tooling to reinforce the blocks. So what did happen back then ?

Yenko may have had rights to use the tooling; just not exclusive rights.

The finished block I saw photos of is a 3946053 Winters casting, circa 1984. Very dark grey.

[markus37]

Yenko was assigned rights in 1974, began producing blocks in 1976 and continued thru about 1983. His blocks were initially cast by Winters and after several price increases molds, patterns etc. we're sent to Lockport..more price increases led to Paul Wright ,who machined the blocks to take over the casting also..Paul made changes to the molds and cast blocks for several years. I have his records.This info is covered in my book " THE YENKO ERA...continued. Canonsburg and beyond "

[COPO_Anders]

Yenko may have had rights to use the tooling; just not exclusive rights.

The finished block I saw photos of is a 3946053 Winters casting, circa 1984. Very dark grey.

Ok, but I was thinking if the tooling was changed by Yenko to make the blocks stronger, then the 1984 GM-blocks would not look the same as the blocks made before Yenko produced them. But of course they could have changed the tooling back to the way it was originally.

[markus37]

My notes indicate that GM retained one or more sets of molds etc at Winters. In addition to those provided to Yenko

[EZ Nova]

Thanks guys.

So know one know what a small "2" mean in the casting number?

[black69]

Thanks guys.

So know one know what a small "2" mean in the casting number?

I don't think it means anything. All I could speculate is they assigned that pn ahead of time in GM documentation, and the size of the 2 could have given engineering a way to run 2 different block designs with the same frozen pn they could not change. That's all I can think of. Small 2 could be first run, and if they had problems, then the large 2 is the second run before the block was released for use in the camaro and the 2 vettes. Who knows. Odd things happen to low production special things.

[Peter426]

Yenko was assigned rights in 1974, began producing blocks in 1976 and continued thru about 1983.

https://image.ibb.co/efuLfm/yenko.jpg