Solid core ZL-1 block

[Steve Antonucci]

I just saw this item on the "bay":4540873297

It is a solid core aluminum block of the ZL-1 persuasion. Can anyone tell me
what exactly a solid core block would be used for? Perhaps racing only, via
1/4 mile at a time.

This is an oddity. I'd love to know members opinions on this.

Steve

[Joe L.]

Re: Solid core ZL-1 block

Steve-----

This sort of block can be used for 1/4 mile type racing applications only. I have no knowledge that GM ever offered such a block, but they may have as evidenced by the GM casting number on this block. It would be illegal for anyone other than GM to produce a block with this number on it. As evidenced by the "LC" in the center of the Winter's "snow flake", this block was likely cast by some other entity.

Sometimes, in years past (and, even the present) blocks used for 1/4 mile racing applications have their coolant passages "filled" with various solids in order to strengthen and "stabilize" the block. This applies to both cast iron and aluminum blocks.

Anyone that would pay any serious money for a block like this is out of their mind. For the kind of racing applications that need a block this stout, cast iron would be a far better choice than aluminum.

[Steve Antonucci]

Re: Solid core ZL-1 block

Joe,

That's what caught my attention. I've seen a number of these before, but never
a cast solid core block before. Interesting !

Ebay has taught us that there are indeed many people "out of their minds"
these days. The whole day 2 thing has me confused anymore ! Remember last
year people bid on that beat-up ZL-1 block that was filled with a cement type
material? It went for close to $2,500.00 as I recall. Now this one for
$4,000.00 plus. It will continue. Knowing a little about the history of these
blocks makes me wonder why so many people would get caught up in the mystique
of them and pay big bucks to own one. Other than the ZL-1's, no Yenko or
other "supercar" ever came with one of these originally. So, what gives?

Steve

[Michael H.]

Re: Solid core ZL-1 block

Interesting that the casting number, 3946052, is very close to the casting number of the original open chamber aluminum heads for mid 1969. Must have come off the drawing about the same time. I've heard of these solid blocks years ago but never actually saw one. Thought it was just wishfull thinking by some of the Pro Stock Camaro guys in 69.

[Joe L.]

Re: Solid core ZL-1 block

Michael----

GM #3946052 was the casting number used for 1969 ZL-1 blocks. Most, if not all, of those blocks had normal cooling passages. Since this block was not manufactured with cooling passages, it really shouldn't even have the 3946052 casting number on it. I would say that a block without cooling passages would be "significantly different enough" to warrant a different casting number.

I strongly suspect that these blocks were "run off" of original GM tooling but not under the auspices of GM. Yenko purchased the production rights for this block from GM after about 1972, or so. So, he may have commissioned some foundry to manufacture these blocks using the original tooling. In that circumstance I don't think that they may have been too careful about changing the casting number.

[Steve Antonucci]

Re: Solid core ZL-1 block

Amazing how a little thing called ebay educates so many - huh?

Here's a slight segway, but not too far off target. I always find these types
of topics fun to investigate. Sadly, I'm 30 years too late. In any event, do
any members here know of a forum or gathering where racers "from the day" still
get together? The reason I posted the question originally was because the
block looked legitimate and I've never even heard of one of these before. As
Joe mentioned, aluminum blocks were filled with "stabilizing material" in an
effort to beef them up. But this thing is a whole other story !

Anyone else have input on this one?

Steve

[Michael H.]

Re: Solid core ZL-1 block

Yep, you are correct. I was thinking of the part number for the AL block instead of the casting number. (was something like 3952318 or 518?)

Makes sense that Yenko may have actually made these in 1972, "after the fact" but I wonder about the cast date? I suppose it was never changed after Yenko started making blocks?

[Michael H.]

Re: Solid core ZL-1 block

I'm amazed at the amount of weird factory race parts that show up on ebay. I suppose a lot of items come out of garages for ebay than do for swap meets because the old people that have this stuff have no interest in hauling it to a swap meet.

I don't know about a drag racers reunion but I do know that a lot of old SCCA racers gather at the vintage road race meets today. Some really interesting cars keep coming out of the woodwork, many of which are still exactly the same as they were 30 or 40 years ago. Also amazing is the number of old racers that come to these events, some with the same cars that they raced in the 50's or 60's. If you're located in the central US, check out the July meet at Road America.

[Clem Z.]

Re: Solid core ZL-1 block

don yenko sold the solid block i believe when he was recasting the GM ZL-1 blocks.

[Bill Stephenson]

Re: Solid core ZL-1 block

--------Hard-blocking is a common drag racing practice. When I was racing my old 70 Chevelle (Red Alert) I used a 1973 dated 454 iron block and took it out to .100 over for 480 cubic inches. We then filled the water passages up half way to give the walls the needed stability for an engine in the 750/775HP/7000RPM range. Funny part was that even with the water passages filled up half way the engine ran very cool. I think I could have run it on the street if I had been crazy enough!
--------These solid blocks are around. Just run them on alchohol. Between the cool running of the alchohol and the heat dissipation ability of the aluminum they can be run on the dragstrip with no problem...........Bill S

[John H.]

Re: Solid core ZL-1 block

The NHRA rules for Top Fuel and Funny Cars for 2005 now require solid/forged blocks for all fuel cars (no cast blocks permitted); too many oildowns last season from fuel cars with cast blocks that robbed TV time.