[prophet455]

Hello all,
Quick question, as I understand it the heads on the model J 400 for 1970 was the 13. The question is, was this the same for the 4 speed cars?

[poncho-mike]

There is some inconsistencies in what people report on 400 4-spd A and F-bodies.

I have seen at least two 70 Formula 400 4-spds with 13 heads. One was a fairly low mileage car that was for sale, and I verified it had the correct VIN. I have seen other Formula 400s with 12 heads that date code matched the block. On the A-body side, I would say that probably 75% of the WTs I've seen installed in GTOs had 12s. I have never seen a 400 4-spd GP, all the manual cars I've ever seen had 455s.

[prophet455]

Thanks,
My GP was a "j" with 400 but the original motor is long gone. I have a 70 400 with 13s that I think would be a lot closer to correct. (Wrong block code of course).

[unruhjonny]

although this may seem a combative comment, it isn't intended as such;

I have never, and I mean NEVER heard of a manual transmission '70 Formula Firebird, or Tempest/Lemans/GTO that was reported to be original, and having #13 heads;
There has been this myth (that I previously thought was legit) that a few 1970 RAIII/auto cars came with #13 heads - but I pretty sure that this has been thoroughly dismissed by now.

According to my Pete McCarthy book, the '70 GP 400/mt engine was a WX engine (as opposed to the WT used in the A bodies and Firebird Formulas);
This book says the GP-WX engine had 13's.

[Joe's Garage]

Manual transmission and automatic transmission - they ALL got the "13"s in the Grand Prixs.

The "13" heads were installed on a majority of 400/350HP engines in Firebirds and GTOs/LeMans/Tempests.

I haven't had experience with or owned ANY 1970 base Firebirds, but of the TEN 400/350HP manual transmission GTOs we've owned, only TWO had the "12" heads.

Everything else had "13" heads, including EVERY SINGLE 400/350HP automatic transmission GTO - been thru thirteen of those.

Known of and/or owned eight RAIII 1970 GTOs and Judges - five 4-speeds and three automatics. ALL of those had the "12" heads.

[unruhjonny]

Joe, I'm not looking to get into an argument with you;
I chimed in only because this was a question about a Grand Prix engine, and erroneous Firebird/GTO engine was offered.

A 1970 modely year car is right now fourty seven years old, and I would suggest that:
1) manual transmission cars were typically driven harder than automatic cars - as such, there was a higher likelyhood of parts being changed when a rebuild of sorts was warranted
2) #13 heads were made in much greater supply than #12 heads;
Since I have access to neither Grand Prix, or A-body production figures all I can cite is Firebird;
Production totals:
WT+WS+YZ = 3,070 (40%)
YS = 4,638 (60%)
I am willing to suggest that in the A-body cars, the percentanges are much more exxadurated than this.

... This all lends to the credance that when engine rebuilds or replacements were concerned, odds are it was more cost effective to purchase or trade across for a set of 13's.
I would also suggest that only a statistical minority of manual transmission cars didn't have a rebuild of sorts within the first handful of years - making identifying original components a little more tricky.

We all agree that the GP recieved 13 heads - and for this part of the forum, and for the original poster's question, that's all that matters.

[Joe's Garage]

I was just posting our experience - didn't mean to be argumentative. I apologize.

My Dad's had at least two 1970 GTOs since the dawn of time! OK, that's an exaggeration, he actually started buying them in 1977 and got as high as eleven a few years ago. We've thinned it down to six. You could say they are his favorite Pontiac.

We can agree that ALL the 400-equipped 1970 Grand Prixs probably left the factory with "13" heads, unless there was some mix-up on the production line. Stuff happens. Just like all the 455 1970 GTOs and Grand Prixs were supposed to get "64" heads.

I myself have seen quite a few 1970 "matching-number" GTOs with assorted, incorrect D-port heads. Most likely, as you suggested, as a result of damage or simple swap outs during rebuild.

Enjoy your day AND your Pontiacs!!

[poncho-mike]

In 1982, I bought a 1970 Formula 400, Lucy Blue, auto with no a/c. It had about 60K miles on it and I loved in, but I wanted a 4-spd. A few years later, I found a low mileage 1970 Formula 400 4-spd with a/c. I liked the car, hated the color (light green). It was a one owner car and I remember the owner knew little about cars. The car appeared 100% original, except it had 13 heads. The heads date matched the cowl tag and all dates matched up. The owner was an engineer and had all of his service records on the car. If it had been a better color, I would have bought it. I passed on the car.

Also in the 80s, I pulled a 70 WT out of a Formula in a junk yard. Dates matched on the parts, including the original carb. It had a 2-bolt block and also carried 13 heads. Both cars were pretty much original, and I don't think they had been tampered with.

[Keith Vrabec]

13 on GP had a few