[6TEE8GTO]

I had thought that the #12 castings were 1970 Ram Air III M/T heads? On another board someone who seems to have a lot of Pontiac knowledge says they are not rare, are common and were found on base 400 cars? I thought that the base cars in '70 got the 16 castings? So #12 heads are not that rare?

[Peje]

To my knowledge #12 heads was also used in base 350hp M/T GTO.Autos got #13.
1970 Ram Air III was #12 both on stick and auto.
Big valve #16 was used in 1968 both on std 400 and 400HO(GTO)
But as always,correct me if I`m wrong.

[TinInjun]

http://www.wallaceracing.com/head1.htm
Bill Bowman is also a member on this board.

[70pontiaction]

In my experience and observation:

All the 1970 GTO/Firebird 400 335/350hp manual trans engines got "12" heads.

All the 1970 GTO/Firebird 400 335/350hp auto trans engines got "13" heads.

All the 1970 Grand Prix/full size 400 350hp got "13" heads.

All the 1970 RAIII 366/345hp engines got "12" heads. Any transmission.

It is kind of funny when you tell someone their "rare" RAIII heads
probably didn't leave Pontiac on a vehicle with Ram Air.

I believe some 1969 350hp manual trans engines got "48" heads, too.
With "62" heads on the rest and on all the automatics.

In 1968 "16" heads were strictly 400/428 4bbl except Ram Air I or II.

[Peje]

And a person claim that #12 heads have 66cc in combustion chamber.How correct is that?

[bigborehunter]

#12 heads would be 72 ccs, minimum, just like #13s.

[marxjunk]

not rare...at all...

['ol Pinion head]

Originally Posted by bigborehunter

#12 heads would be 72 ccs, minimum, just like #13s.

have never ever cc'ed a virgin #13 head that came in at 72 cc, all have had stock chambers, non sunkedn valves & have come in between 77 & 80 cc's a chamber.. CC'ed my first three sets over 25 years ago. 12's I've cc'ed in the 72-73 cc range, but have only had one set that was off an original never messed with engine. The others had been through the machine shop at least once.

Back to the OP, the 70 model 330 HP 400 auto code XV had the small valve '70 model 16 heads. Have ran across several '70 XV coded 400 engines. One set on an original XV engine in an atoll blue '70 1/2 GT-37.

Whoever is spouting off the 12's aren't that rare, at least in the south, obviously hasn't bought and sold a bunch of big valve D-port heads over the last 3 decades, & I'd wager the same party is looking for a bargain basement deal

[Peje]

What are we talking about? General 400 heads for 1970 or for GTO? Or Firebird? Or T-37,GT-37?
No 16 heads for 1970 GTO.I think we can agree on that.
So,what was the difference between #12 and #13 exept comb ch? My vote is diff valvesprings.

[rexs73gto]

The diff. between 12's & 13's are 12's were for the 4spd. cars & 13's were for auto's .

['ol Pinion head]

Originally Posted by rexs73gto

The diff. between 12's & 13's are 12's were for the 4spd. cars & 13's were for auto's .

While #12's were used on '70 WT 400's (base 400 4bbl man trans), 12's were also used on both '70 WS (man trans) & automatic YZ (auto) RAIII engines.

[6TEE8GTO]

Originally Posted by 'ol Pinion head

While #12's were used on '70 WT 400's (base 400 4bbl man trans), 12's were also used on both '70 WS (man trans) & automatic YZ (auto) RAIII engines.

Depending what source you go with, it appears that in 1970, 40,149 GTOs and Judges were built in total. 16,033 GTOs and Judges had manual trans, 24,116 had automatics.
Even if they put the #12 heads on EVERY manual trans GTO built in 1970, that means 16,000 sets of #12 heads. Contrast that with about 80,000 #16 castings alone just for 1968, I'd say that relative to total production of the other castings, #12 heads are somewhat more difficult to locate some 44 years later.....

[muscle_collector]

don't forget to add all the 4 speed 400 firebirds and the ram air 3 trans ams