Mystery BBC head casting number 1X157129AC

[6T9chevelle]

I aquired a set of rect. port BBC iron heads with a casting number which I can find no info on. Any help would be appreciated. The date code is 58 which is odd as well.


Jeff

[bobby]

I came up with you twice at the top of google and this

http://kansascity.craigslist.org/pts/1547485115.html
http://www.clubhotrod.com/forums/showthread.php?t=39607


You weren't looking a couple of yer ago were you?

http://www.ls1tech.com/forums/small-...ese-heads.html


there must be another number on them or you wrote down the wrong thing, unless they are super rare one off piece's

Goodluck

[BillK]

How about a picture of the heads showing the casting number ?

[Kenny Wigington]

Those were probably some of Smokey 's heads....

[Monte Howard]

I bet it is heads off of a 88 Tonawanda motor.

[6T9chevelle]

Here is a pic of the casting number.

[ss3011]

The numbering indicates they are Experimental heads, that must have been smuggled out of GM.

[Chris "drooze" Wertman]

And here is a pic of our new driver



Im joking, but small pic......cant see......

Originally Posted by 6T9chevelle

Here is a pic of the casting number.

[njk53]

There is a high probability these are altered production heads that got out of GM.

The 1X before a production part number was and still is a designator so the part can be tracked in the GM system. Then the part could be put on a bill of materials list to be used on a development/early build vehicle or placed on an existing test vehicle. If the change to the part proves out the release engineer requests a new part number for production.

The 1X generally means there was a modification to the production part that was big enough to require a drawing change. The change did not have to be major just enough to alter the drawing. The AC means there were 3 changes made to the prototype part.

Usually the 1X part is taken off of the vehicle and given back to the release engineer who usually would scrap them. I have seen a lot of good stuff get thrown out but it looks like this set of heads got away.

The production part number behind the 1X is really what you have with an alteration.

[6T9chevelle]

That is an excellent bit of info. Do you have any idea what heads these could have been based on? Also GM typically uses a 3 digit date code. Any info on the 2 digit code?


Jeff