72 Pontiac GTO Questions

[stavanzer]

Could a "Day 2" '72 GTO have the triple carb setup that was used on the earlier GTO's?

I want to build the MPC/AMT GTO that way, but I'm not sure that the tri-power is a Legit Mod.

It would sure be nice to see this one come back, Round2.

[Snake45]

Yes, one COULD be built that way. But Pontiac tri-power was long passe by 1972. It was discontinued for 1967 IIRC and everyone was working with single or double 4-bbls ever since. (Yeah, Chevy had 3x2 on the 427 as late as '69 but it wasn't the hottest setup.) The last great gasp of three-twos was on the '69-'70 ('71?) Mopars. 

So build it that way if you want, but it would be kind of unusual. 

[Carmak]

I have a 1:1 71 GTO and it is more of a bugeye or triangle mesh air cleaner on Holley and an aluminum intake day 2 car. Mix in some slots and you are there.

Edited June 4, 2020 by Carmak
Add image

[Rodent]

IIRC, a 389 intake manifold doesn't fit a 400 due to cylinder head changes, so it couldn't be done with factory parts. I am sure there were aftermarket 3x2 and 2x4 manifolds for the 400, so go for it if it floats your boat. Someone did it in 1:1 I am sure. 

[larman]

Last factory tri-power Pontiacs were '66, but in a modified car, anything is possible. Suppose you had a '72 and you terminally blew up the motor, a junkyard 421 or GTO 389 with a 3x2 set up might be a good theoretical swap, if you could find them. But, As Snake said, by '72 or later, a single or dual 4bbl set up on a 400 or 455 would be more likely. Or a BBC transplant for that matter. 

[Can-Con]

I copied this from the Q&A  section from  pontiactripower.com 

" First, a 455 has the same deck heigth as the 326, 350, 389, 400, 421, and 428. That said, the head is the critical factor. Heads from 61 to 64 have different water passages, a different bolt pattern, and a different angle where they meet the intake than do the 65 and later heads.

Therefore, what most people want is the popular 65 or 66 tripower to fit the improved and readily available 65 up heads. A 65 or 66 tripower will bolt directly to the 65 to 71 Pontiac heads. However, starting in 72, Pontiac has an extra exhaust crossover port in one of the heads. The 6X head is a mid-70s head and has this extra port. The 65/66 intake will not cover this port. There is no special intake gasket to accomplish this. The force of the exhaust is too intense for a gasket to stop. Best method is to have a machine shop fill this extra port while you are having the head work done. At least one customer filed this port while the head was on the car, using JB Weldand reports no problems. I am much more comfortable with the first method."

So, id dosen't look like all that much work but I agree with Snake and the others, A good 4bbl would be much more common and just be a better choice for a street driven car at the time.

The only real reason for a tripower over a well set up 4bbl would be for looks but even then it would look old and "out of fashion" for a car of that vintage.

Edited June 3, 2020 by Can-Con

[stavanzer]

Thanks, Gents. I'll scrap the Trips, and find a good Bug Eye Air Cleaner, and assemble the rest of the motor stock.

Carmak. You said Slot Mags? Would Cragars work too?

[Snake45]

49 minutes ago, alexis said:

Thanks, Gents. I'll scrap the Trips, and find a good Bug Eye Air Cleaner, and assemble the rest of the motor stock.

Carmak. You said Slot Mags? Would Cragars work too?

Cragars would work fine for this. So would any of the slot mags, Americans, Keystones, etc. I believe the "Super Trick" plain disk wheels were also coming into use by this time. 

[stavanzer]

Great, Thanks!  I have plenty of Mags. I'm thinking of using the set from the AMT '65 El Camino, or the AMT '40 Ford Coupe.

[Mark]

Maybe go with an updated tri-power setup, using the carbs from a Corvette.  Chrysler hung in with the Six Pack through '71, it was probably a better all-around package than the Hemi for most buyers back then.

[Snake45]

54 minutes ago, alexis said:

Great, Thanks!  I have plenty of Mags. I'm thinking of using the set from the AMT '65 El Camino, or the AMT '40 Ford Coupe.

Those would both be fine, also the ones in the '72 Nova. 

[stavanzer]

Ah, I've got that kit too. But, the Elky Mags are in the box with the GTO.

[Carmak]

The Cragar mags in the 65 El Camino kit are really nice wheels and will look great!

Just an FYI for the 1:1 Pontiac followers the 65 and 66 factory tri-power intake will fit every Pontiac engine 65 and later (except the 301). The caveat is that a filler plate (or special intake gasket with the filler plate built in) is needed for the exhaust crossover after 71 as the crossover opening got slightly taller in 72. In the 80's while I was in high school a friend put a 65 389 4bl intake and AFB on a 75 400 in a Catalina to upgrade to a 4bl. He figured out the block off plate on his own. Most currently available aftermarket intakes are designed to seal to all heads 65 and later (except 301).

[Scott8950]

12 hours ago, Can-Con said:

 

The only real reason for a tripower over a well set up 4bbl would be for looks but even then it would look old and "out of fashion" for a car of that vintage.

Back in the 80's i had a 77 camaro that had a 67 corvette 427 engine with the tri power carbs still on it. The engine was stock with exception of a larger cam and a set of headers, 400 turbo trans with 3500 convertor and 4.11 gears. It was probably one of the most fun cars I've owned, you could kill a set of rear tires in a weekend ?

[Can-Con]

16 hours ago, Scott8950 said:

Back in the 80's i had a 77 camaro that had a 67 corvette 427 engine with the tri power carbs still on it. The engine was stock with exception of a larger cam and a set of headers, 400 turbo trans with 3500 convertor and 4.11 gears. It was probably one of the most fun cars I've owned, you could kill a set of rear tires in a weekend ?

 , , And that's what makes building street machines and hot rods fun. everyone had different tastes and ideas on how they want their car.

[Deuces ll]

On 6/3/2020 at 10:58 PM, Scott8950 said:

Back in the 80's i had a 77 camaro that had a 67 corvette 427 engine with the tri power carbs still on it. The engine was stock with exception of a larger cam and a set of headers, 400 turbo trans with 3500 convertor and 4.11 gears. It was probably one of the most fun cars I've owned, you could kill a set of rear tires in a weekend ?

????