Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

Here is a pic of the casting number.

http://i151.photobucket.com/albums/s...2/bbcheads.jpg

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

I looked for it on www.mortec.com and that number doesn't show up. Good luck finding it.
Danny Durham

Re: Mystery BBC head casting number 1X157129AC
 

And here is a pic of our new driver

http://farm5.static.flickr.com/4054/...94a11482f6.jpg

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

Re: Mystery BBC head casting number 1X157129AC
 

Here is the link to the craigslist ad I found them on. It clearly shows the casting number for the disbelievers or the visually impaired.

http://desmoines.craigslist.org/pts/1557770912.html

Re: Mystery BBC head casting number 1X157129AC
 

The ad does say they are rectangle port but there isn't a picture showing them, they could be a newer vortec head or who knows???????????

Re: Mystery BBC head casting number 1X157129AC
 

Date code would be a good starting point.

Re: Mystery BBC head casting number 1X157129AC
 

My best guess is they are aftermarket heads. I have never seen any Chevy head with casting numbers like that. GM as far as I know only used numbers in their Chevy castings. Many heads have a seperate letter cast on the head but it was seperated from the actual casting number. An X was found on some small block heads as well as some other letters.A Date is usually also cast on the head if it's OEM.

Re: Mystery BBC head casting number 1X157129AC
 

Does anyone own a set of the BBC heads that GM experimented with on a small block chevy or does anyone own the BBC hemi experimental heads. Just curious

Re: Mystery BBC head casting number 1X157129AC
 

The date code is cast in as well which is 58.

Re: Mystery BBC head casting number 1X157129AC
 

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.

Re: Mystery BBC head casting number 1X157129AC
 

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

Re: Mystery BBC head casting number 1X157129AC
 

I dug the heads out and looked more closely at them. They also have CFD cast into them which would verify that they are GM and they also have HIGH PERF cast into them.

Re: Mystery BBC head casting number 1X157129AC
 

I found a casting number which is very close to the one I am trying to find info on.

10051129...........rect..........Bowtie, Aluminum "raw"
casting, Symmetrical ports

If you compare the numbers change my x to a 0 and the 051 to 157. Those heads are high perf aluminum heads which are raw castings and made in 1988 which would explain the 58 date code. Could these possibly be an iron version which never made it to production?

Re: Mystery BBC head casting number 1X157129AC
 

The PN 157129 was probably the production released casting, which could have been the original production intent part before regular production started. The 1X placed before it means there was an alteration to PN 157129 before regular production started. As stated before, the prototype was changed 3 times. First change was designated AA, the second change AB and third change was AC. This went on the drawing for tracking purposes.

There even may not have been a cylinder head PN 157129 that ever got put on a regular production vehicle.

For example what could have happened was this PN was internally released for production and put on a Bill of Materials for non-salable vehicle builds which were used from everything from marketing to durability. There may have been an improvement made, a problem discovered during testing, or a cost savings that drove a change to the part/drawing. The 1X allowed the change to be made and placed on a build/test vehicle. If the change was satisfactory the 1X part number was changed to a new production number.

The finding of a casting number that was close to this one doesn't mean a thing. The part numbers were issued by an analyst. For example 157129 could be a BB application and 157130 could have been a 6 cylinder application so don't go by similar part numbers.