Mystery BBC head casting number 1X157129AC - Page 2

RULER · 01-30-2010, 05:00 AM

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???????????

Adger Smith · 01-30-2010, 07:58 AM

Date code would be a good starting point.

Rich Biebel · 01-30-2010, 08:55 AM

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.

mannymen · 01-30-2010, 11:47 AM

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

6T9chevelle · 01-30-2010, 01:07 PM

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

njk53 · 01-30-2010, 01:12 PM

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 · 01-30-2010, 09:06 PM

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

6T9chevelle · 02-01-2010, 03:50 AM

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.

6T9chevelle · 02-01-2010, 01:08 PM

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?

njk53 · 02-01-2010, 01:37 PM

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.

01-30-2010, 05:00 AM	#11
RULER Member Join Date: Jan 2006 Posts: 221 Likes: 15 Liked 58 Times in 18 Posts	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???????????

01-30-2010, 07:58 AM	#12
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Mystery BBC head casting number 1X157129AC Date code would be a good starting point. __________________ Adger Smith (Former SS)

01-30-2010, 08:55 AM	#13
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	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. __________________ Rich Biebel S/C 1479 Stock 147R

01-30-2010, 11:47 AM	#14
mannymen Senior Member Join Date: Apr 2003 Posts: 728 Likes: 5 Liked 13 Times in 7 Posts	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 __________________ N/A

01-30-2010, 01:07 PM	#15
6T9chevelle Junior Member Join Date: Oct 2006 Location: Lincoln Posts: 39 Likes: 0 Liked 0 Times in 0 Posts	Re: Mystery BBC head casting number 1X157129AC The date code is cast in as well which is 58.

01-30-2010, 01:12 PM	#16
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	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. __________________ Nelson Kowal Stock 345 Last edited by njk53; 01-30-2010 at 01:17 PM.

01-30-2010, 09:06 PM	#17
6T9chevelle Junior Member Join Date: Oct 2006 Location: Lincoln Posts: 39 Likes: 0 Liked 0 Times in 0 Posts	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

02-01-2010, 03:50 AM	#18
6T9chevelle Junior Member Join Date: Oct 2006 Location: Lincoln Posts: 39 Likes: 0 Liked 0 Times in 0 Posts	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.

02-01-2010, 01:08 PM	#19
6T9chevelle Junior Member Join Date: Oct 2006 Location: Lincoln Posts: 39 Likes: 0 Liked 0 Times in 0 Posts	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?

02-01-2010, 01:37 PM	#20
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	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. __________________ Nelson Kowal Stock 345 Last edited by njk53; 02-01-2010 at 01:40 PM.