Mystery BBC head casting number 1X157129AC - Page 2

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.

02-01-2010, 03:50 AM	#1
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	#2
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	#3
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.