[gtohurstjudge]

The 70 Judge I'm working on has no. 13 cylinder
head castings. If I'm reading my GTOAA ID book correctly
it is supposed to have no.12's. Is that right? It is a Ram III
automatic trans non air Judge.

[Bermuda Blue]

i believe ra engines got 12s regardless of transmission.

['ol Pinion head]

12's, every original. I've examined.

[The Boss]

12's

[KenD]

#12's.

[RATTCRUSHER455]

12's

[PaulatFast]

12's

[Ron Landis]

I would investigate further. Not to dispute anyone...but if the date codes fit...well...stranger things have happened at Pontiac...especially when the car involved is an automatic. Anyone recall the DOCUMENTED '69 RA III T/A auto/air car in Cali with "62" casting heads on it? I fought with the GTOAA for years after they tried to deduct 10 points off of my 50k mile original '69 auto because they swore it should have "16"s on it. Finally got thru to them when a 29k mile original auto car pulled in with "62" castings...documented original car also. My car took 1st in Restored class that year. I had to do a nationwide survey via "The Legend" and found ZERO documented '69s delivered with "16"s. Just sayin'...not entirely out of the question that your's are correct...and I would DEFINATELY find out for sure before initiating any action to "fix" it. In any event...prepare yourself for the controversy. Not to coin a phrase...but some folks just "can't handle the truth!" JMHO. Ron

['ol Pinion head]

Have never ever ran across original '69 production dated & installed 16 big valve D-ports. Have had a bunch of them. Have easily looked at several hundred original '69 YS's, XH's, XF's, all had their 62's. Many of us would argue 16's were a typo in Pete's book.


I'll leave this with these statements:
13's have always been 20 times easier to come up with than 12's, esp if one needed a pair of 12's to date a TransAm (late J of '69 & later dated 12's). It's amazing how the 78-80cc chamber 13's magically make it on to the "born with numbers matching" 70 400 RAIII engines. Puppy mill "restorers" cutting corners couldn't have anything to do with that

[Kenth]

OPH, i believe big valve #16´s were used only on early 1969 Firebird RAIII w/AT, code YW.
At least MPC suggests so and they do exist:

[Kenth]

Also, the #12 casting # indicates 66.27cc combustion chambers, stronger valvesprings and no oil sheilds due to the stronger valve springs.
No RamAir heads uses oil shields on the valve springs.
These are the 1970 RAIII w/MT and AT, heads, also used on 400 w/MT.

#13 heads has 75.70cc combustion chambers uses "standard" strength valvesprings w/oil shields.
These heads were used on 350hp 400 w/AT only.

[gtohurstjudge]

Thanks for all the responses.......It sounds like these heads
are not the originals.....We'll probably leave the 13's on it for now since it
isn't going to a point judged meet in the near future. The owner does Multi-make
shows, where the casting numbers on the heads would be irrelevant. I can
understand why a previous owner would have bought the wrong heads, as it plainly
states in the GTO restoration guide in the engine section that all automatic
cars had 13's in 1970.......however if you flip over to the chapter on Ram Air engines,
it states that the Ram Air III used no. 12 cylinder heads. I was initially fooled by
the first passage in the book myself, but found no. 12's listed under the Ram Air chapter
after everyone on the forum said that 12's should have been used. Thanks again to everyone
for their help and input.

['ol Pinion head]

Originally Posted by Kenth

OPH, i believe big valve #16´s were used only on early 1969 Firebird RAIII w/AT, code YW.
At least MPC suggests so and they do exist:

Kenth, respectfully, I don't trust MPC's for how the assembly lines actually built cars. Have ran across too many examples of even relatively close dated MPC's being incorrect. The distributors factory installed in early to mid production '69 WT's & RAIII engines are one example... so many times not what the MPC states.

Would also love to see quite a few original low mile uncut #12's cc'ed. The last set of virgin #12's I had had gone through for a '70 YZ engine I owned we cc'ed 4 chambers, & all were in the 71cc range. Also carefully cc'ed several pair of relatively low mile 13's in the early to mid 90's, & every pair had came in between 78 & 80 cc, no sunken valves, nice cores.

[PaulatFast]

The MPC's are not gospel and have been proven incorrect on many occasions...

[70pontiaction]

I've owned two RAIII T400 cars myself and both had 12s.
I've also owned three different WT 400/350hp 4spd cars with 12s.

Only saw the 13s on YS engines in T400 GTOs or on T400 Grand Prixs.

[Peje]

We might as well pick up the debate around heads 62/48.

Chamber cc on 62?(large valve)
Chamber cc on 48?

Some say 72cc some say 75-80cc. Anyone have TRUTH here? and NO GUESSING!!

Hard to believe that #13 had smaller cc than #62 when the compression began to drop in 1970.

Only difference between 48/62 was use of different valvesprings Man vs Auto?

[Kenth]

Originally Posted by 'ol Pinion head

Kenth, respectfully, I don't trust MPC's for how the assembly lines actually built cars. Have ran across too many examples of even relatively close dated MPC's being incorrect. The distributors factory installed in early to mid production '69 WT's & RAIII engines are one example... so many times not what the MPC states.

Would also love to see quite a few original low mile uncut #12's cc'ed. The last set of virgin #12's I had had gone through for a '70 YZ engine I owned we cc'ed 4 chambers, & all were in the 71cc range. Also carefully cc'ed several pair of relatively low mile 13's in the early to mid 90's, & every pair had came in between 78 & 80 cc, no sunken valves, nice cores.

I agree about the MPC´s not to be trusted all the way, still, we have a big-valve #16 set of heads with 1969 production date in my picture?

[Kenth]

I have found the "eyebrows" in combustion chambers being smaller in #48 and #12 heads than the eyebrows in 1968-69 #16, 1969 #62 and 1970 #13.
Just like the eyebrows in 6X-4 350 heads are smaller than 6x-8?
It´s quite easy to see, by the naked eye, that the chambers of the #48´s and #12´s are smaller.

This may indicate that also #12´s initially were aimed for the 1970 350H.O. that never came into production because of low interest?
Just like the #48 350H.O. heads ended up on the 1969 RAIII/400-428w/MT, due to slow sales of the 350H.O.?

#13 heads chambers would be slightly larger than #62´s due to the compression drop 1970?
At least the lenght of valves, being shorter in the #13 heads, indicates this.

[PunchT37]

Originally Posted by Kenth

I have found the "eyebrows" in combustion chambers being smaller in #48 and #12 heads than the eyebrows in 1968-69 #16, 1969 #62 and 1970 #13.
Just like the eyebrows in 6X-4 350 heads are smaller than 6x-8?
It´s quite easy to see, by the naked eye, that the chambers of the #48´s and #12´s are smaller.

This may indicate that also #12´s initially were aimed for the 1970 350H.O. that never came into production because of low interest?
Just like the #48 350H.O. heads ended up on the 1969 RAIII/400-428w/MT, due to slow sales of the 350H.O.?

#13 heads chambers would be slightly larger than #62´s due to the compression drop 1970?
At least the lenght of valves, being shorter in the #13 heads, indicates this.

Interesting. I never thought of that. Maybe they had plans for the last high compression 350 for 1970.
Could be the 350 HO and the OHC 6 didn`t sell well enough so they were both dropped for `70.

[Tony69]

Interesting topic, does anybody have the specs of the various valve springs used by the factory?