[Bermuda Blue]

have seen a number of stamped 2s in my day but have never heard that they were only installed in early GTOs.

http://www.ebay.com/itm/70-PONTIAC-G...b4dfa2&vxp=mtr

from the auction for those who can't link...

" These rebuilt #12 10.5 to 1 compression heads are from a 1970 GTO and both have an early manufacture date of November (K) 21 1969. Being an early casting, the #12 has the 2 stamped as a production transition only found on low serial number 1970 GTOs not 1970 1/2 Trans Ams, which I bought them for. The heads were machined and pressure checked by a reputable shop (receipt included). All new intake valves were installed. Stock 3/8" Bottleneck rocker studs included. Ready to bolt on. The heads weigh about 65 lbs each so shipping will run $185 unless they are picked up."

First, I don't consider K and early casting. Secondly, since all engines originated from pontiac, I don't see how engines with a full 12 casting were isolated and installed in trans ams. Sounds like good story though. The guy is probably not comfortable with the stamped 2 and doesn't realize the heads are probably legitimate #12 heads. Can't say I blame him though.

[marxjunk]

sure they arent 13s?

[Bermuda Blue]

would have to CC them to find out since i thinks 12s have the smallest chamber...difficult to fake a chamber size.

[The Boss]

12's weren't being used in F-bodies until very late January or February of 70.

[Bermuda Blue]

Originally Posted by The Boss

12's weren't being used in F-bodies until very late January or February of 70.

Good point. that being the case, the seller's issues in the casting date since K may be considered too early for a late Jan car.

[marxjunk]

ive seen 1 and 2 stamped but not just the 2..you can make and smaller CC ..mill them

im no expert

[The Boss]

I thought the stamped heads were the service replacement ones.

[Bermuda Blue]

I have only see 3 or 4 of these stamped 12s. And if i recall, the casting date matched the other components on the engine.

But stamping the SR heads makes sense.

[Baron Von Zeppelin]

I have a set of 12's dated F249 - the first casting batch.
Have seen at least 3 other posts in threads where guys have had the same F249 dated 12's.

12's and 13's were pretty high production.
Not sure off top of my head anymore - if there any numbers under the valve cover area to ID them or not.

[unruhjonny]

I thought that I read some time ago that rebuilders would do this to have a "matched" pair of heads...??
I hace never heard of this actually being anything that PMD did;
I mean since the '69 #48's were essentially the same as '70 #12's (and '69 #62 about the same as '70 #13's), why would PMD go through the added effort of casting a newer head, then grind off a part of the (or the whole) number, to stamp it differently;
It just doesn't make sense to me.

I'd see it more plausable that someone took creative excersise to make a cylinder head more desireable...

I would also think the full part number would be a better gauge;
as all but the RAIV had the part number visible with the valve cover removed.

[Jason67]

I have original 12 heads dated F249 on my 09E built Judge, no numbers under the valve cover, just the "casting clock", and the 12 is cast.