BBC casting #1X157129AC still a mystery.

[tj310]

I suggest you try and sell them on the Yenko or a Corvette site cause there not legal in stock unless you grind the numbers off and carefully weld on different numbers. Thanx Trevor

[6T9chevelle]

They are open chamber with a taper plug. I believe the exhaust are 1.88.

[Jim Cimarolli]

The little plug has to mean post 1970, and the open chamber almost has to lead me to believe it is a prototype of an over the counter item. Somebody correct me if I'm wrong, but I don't think there was ever a production engine built by GM after 1970 that had a big port open chamber iron cylinder head on it.

[Chris Cogan]

Bowtie Froggie is correct. These heads are from Central Foundry Defiance. The wagon wheel was the old logo. All Central Foundry Sites became part of GM Powertrain in the early 90's, so I would guess that these heads are service replacement heads from 1988. The date code uses a letter for the month (we didn't use I so it wouldn't be confused with a 1), then 3 numbers. First 2 numbers were the day and the last # was the last number of the year. maybe 058, 158, 258, who knows. looks like the pattern had a "sticker" and the numbers didn't get imprinted in the mold. Defiance finished production of the Mark late last year. (8.1 liter block, head and crank) The end of an era for sure. I will try to find out more about the casting #. Take care guys.

[6T9chevelle]

What would a head like this be a replacement for? SS454 truck maybe?

[Rich Biebel]

The last BB open chamber rectangular port head I am familiar with was the 188 casting. That was the last 3 numbers. It was found on crate LS-7's in the late 80's I'm guessing. They had 2.19-1.88 valves and one big difference from the previous 990 heads......hardened seat inserts( stellite) on the exhaust side. Peanut plugs as we called them were only on later heads. No production engine installed in a car or truck ever had those heads on them. GM Performance used to build special vehicles for display or use them for promotion. They also seemed to build some pre production stuff to see if there was interest.........Those heads have to be pretty old. My buddy has an original SS454 pickup and there is no way heads like that were on his truck when it was new.....he replaced the engine with a crate 502 a couple years ago.....