[WARSGTO]

A LITTLE CONFUSED ? ARE 1970 NUMBER 13 HEADS FOR RAMAIR CARS OR NOT . THANKS FOR ANY INPUT .

[WARCHIEF400]

No #13 were not used on RAM AIR motors, #12 were used on both auto and manual RA III motors and #614 heads were used on RAM IV cars.

[gtoric]

#13 were applied to standard 350hp/400ci w/Auto. #12 were used on all RA III & std. 350hp/400ci w/Man. --GTO

#13 used on 350hp/400ci w/Auto. & Man. --GP

#13 used on 330hp/400ci w/Auto, 345hp/400ci w/Auto. #12 used on 330hp/400ci w/Man., 345hp/400ci w/Auto. & Man. --Firebird

[2manyT/A'S]

I have heard from several sources that #13's came on some YZ's (RA3/auto) with air conditioning,but have NOT confirmed this information myself.

[70RamAirIIITA]

According to John Smith's book High Performance Pontiacs 1955-1974/SA books, the 13's as well as the 12's were installed on 1970 RAIII TA's with the YZ block/automatic tranny. 12's were exclusive to the WS RAIII block/4-speed combo. 13's were also put on 1970 non-RAIII 400 YS engines as well.

[2manyT/A'S]

I understood that #13's ALSO had a slightly larger (75cc) chamber than the #12's @ 72cc's.

Also heard that SOME #48's (from 69) had a 68 cc chamber.
Does anybody know anything about that?

[1971WARBIRD]

Also heard that SOME #48's (from 69) had a 68 cc chamber.
Does anybody know anything about that?[/QUOTE]



in 1969 some 48's were meant for the ho350 motors.heard because sales were not as much as expected some lower cc 48's ended up on some 400 ram air III's

[70RamAirIIITA]

Not sure how correct this table is, but here's a link on PontiacPower with specs on every head from 1955-1979. It shows the 12's and 13's having the same 72cc chambers. It also shows both 48 versions of having 72cc chambers as well. But like I said, don't take my word for it; I'm not sure how correct this table is and I'm sure there's always room for speculation.

http://www.pontiacpower.net/headcast.html

[The Boss]

My 70 RA III/Auto with A/C Formula had 12's not 13's.

[70RamAirIIITA]

So much for the 12's-being-exclusive-to-manual-tranny-cars-only theory..................

[GP704SPD]

I have a 70 GP with 4 speed and #13 heads,400 motor

[2manyT/A'S]

I believe ALL 1970 350 HP 400 4 speed designated blocks came with #12's.(non-A/C)

My 70 Formula has them & I have seen several others.

Does your 70 G/P have A/C?

[poncho-mike]

I have seen two known original 70 Formula 400s w/WT engines, one 4-spd and one 3-spd with 13s. I have also seen 70 Formula 400s with WT motors, 4-spds and #12 heads.

I have junked quite a few 70 T/As and 70 Formula 400s with Ram IIIs and automatics. I have never found a YZ block with 13 heads, with or w/o a/c.

Mike

[2manyT/A'S]

Originally Posted by poncho-mike

I have seen two known original 70 Formula 400s w/WT engines, one 4-spd and one 3-spd with 13s.

Mike

Do you recall if theses were A/C or non A/C cars?

['ol Pinion head]

Originally Posted by 70RamAirIIITA

Not sure how correct this table is, but here's a link on PontiacPower with specs on every head from 1955-1979. It shows the 12's and 13's having the same 72cc chambers. It also shows both 48 versions of having 72cc chambers as well. But like I said, don't take my word for it; I'm not sure how correct this table is and I'm sure there's always room for speculation.

http://www.pontiacpower.net/headcast.html

Charts like that are all over the Net & full of bad info. The RallyII wheel ID chart that gets posted on here from time to ime is even worse.

Virgin, uncut, no valves sunk, casting 13's should cc between 78 & 80 cc per chamber. Have personally cc'ed 3 pair of 13's & longtime Pontiac machinist buddy, also came to this same conclusion many moons ago. Something to ponder... IF 12's & 13's were both 72 cc D-port big valve heads... why have two different casting numbers ???


Last... All the original '70 YZ's & WT's I've owned or worked on, have had casting number 12 heads. Yet to run across one with 13's, but def possible, esp very late in the model year.

[2manyT/A'S]

Originally Posted by 'ol Pinion head

Charts like that are all over the Net & full of bad info. The RallyII wheel ID chart that gets posted on here from time to ime is even worse.

Virgin, uncut, no valves sunk, casting 13's should cc between 78 & 80 cc per chamber. Have personally cc'ed 3 pair of 13's & longtime Pontiac machinist buddy, also came to this same conclusion many moons ago. Something to ponder... IF 12's & 13's were both 72 cc D-port big valve heads... why have two different casting numbers ???


Last... All the original '70 YZ's & WT's I've owned or worked on, have had casting number 12 heads. Yet to run across one with 13's, but def possible, esp very late in the model year.

SO....., have you cc'd any #12's for comparison of chamber volume size?
Is there a difference?

Still curious about different chamber volumes available on 1969 # 48's.

[GP704SPD]

My car has A/C but i don't know why that would make a difference.I've had the car since 84 and i don't think it was ever been apart until 93 when i rebuilt it.Bought off of original owner.

[2manyT/A'S]

I think the thought process there was that the #13's with the LARGER chamber would provide a slightly lower CR which would enable the A/C equipped engines to run a bit cooler.

Cars with A/C also generally came with numerically LOWER rear gears.
I think this was because the belts tended to remove themselves at higher RPM's.

['ol Pinion head]

2manyT/A's,

The only loose 12's I've cc'ed came in at 70cc. Other 12's, I've had, ended up selling or trading them off with matching original shortblocks.


On loose 48's, I've had a pair that were lightly surfaced & came in at 64cc. Also had a pair that came in at 69cc. Believe the 350HO versions were 67cc, though have only had one '69 350HO longblock & never cc'ed the original heads off it, they were "good" dates, so ended up splitting that engine up.