# 71 GTO Setup



## 71BlueGTO (8 mo ago)

Hey guys, I’m relatively new to the Pontiac scene. I just inherited a 1971 GTO.
Specs
400 with #96 heads
Forged Pistons 
Mild Cam….Not sure in Specs.
Headers and dual exhaust. 
650 Double Pump Carb
4 Speed MT. 


Im considering changing to a Quick fuel SS780VS.
Does anyone have any information on basic setup or if this is a good choice? Any other information would be great. I read a restrictive exhaust really limits the way the heads flow. And the mufflers installed are really restrictive. Any truth? Thanks for your help guys.


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## BLK69JUDGE (Jun 10, 2010)

welcome
drive it and enjoy as is .....


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## michaelfind (Dec 14, 2018)

Welcome


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## O52 (Jan 27, 2019)

What type of mufflers do you have? 
What do you want in regards to exhaust sound?

And welcome aboard.


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## BearGFR (Aug 25, 2008)

Welcome to the place...

In my opinion, 650 is a little small for a good running Pontiac. Not too long ago I watched an episode of Engine Masters on MT+ that pretty much killed the myth of getting a carb that's "too big". Yes, it's possible but you have to go stupid-big on a stupid-small engine to make it happen --- like putting a 1050 Dominator on a 170 c.i. Ford 6.
The factory QJet that would have been on your 400 was capable of 750, so I wouldn't have any hesitation to got with a 780.

Cheers,
Bear


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## 71BlueGTO (8 mo ago)

O52 said:


> What type of mufflers do you have?
> What do you want in regards to exhaust sound?
> 
> And welcome aboard.


I’m not sure what type of mufflers tbh, but they are quiet and I was looking for more of a muscle car sound….flowmaster series 40’s


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## 71BlueGTO (8 mo ago)

BearGFR said:


> Welcome to the place...
> 
> In my opinion, 650 is a little small for a good running Pontiac. Not too long ago I watched an episode of Engine Masters on MT+ that pretty much killed the myth of getting a carb that's "too big". Yes, it's possible but you have to go stupid-big on a stupid-small engine to make it happen --- like putting a 1050 Dominator on a 170 c.i. Ford 6.
> The factory QJet that would have been on your 400 was capable of 750, so I wouldn't have any hesitation to got with a 780.
> ...


Thanks Bear, Is anyone running the squarebore adapter plate? It still has the stock intake on it.


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## Captainfish#1 (Dec 31, 2017)

71BlueGTO said:


> Thanks Bear, Is anyone running the squarebore adapter plate? It still has the stock intake on it.


I am running the square bore adapter. I do not know for sure but my engine builder claims I am giving up about 15 horses by not going to a proper square bore manifold. Not giving up my aluminum factory manifold for 15 hp


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## Captainfish#1 (Dec 31, 2017)

Captainfish#1 said:


> I am running the square bore adapter. I do not know for sure but my engine builder claims I am giving up about 15 horses by not going to a proper square bore manifold. Not giving up my aluminum factory manifold for 15 hp


If you go the adapter route make sure it is a four hole adapter,not an open one


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## Jared (Apr 19, 2013)

71BlueGTO said:


> I’m not sure what type of mufflers tbh, but they are quiet and I was looking for more of a muscle car sound….flowmaster series 40’s


Mufflers are a very subjective topic. I had a generic version of the flowmaster 40s on mine when I got it. Engine was a very tired low compression 400 and it was pretty loud.


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## O52 (Jan 27, 2019)

A lot of people like the 20" Walker turbo mufflers. They have that classic 'Muscle Car' sound at idle and low speed then they really open up past 2500 RPM. 
NO DRONE either.


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## 71BlueGTO (8 mo ago)

Jared said:


> Mufflers are a very subjective topic. I had a generic version of the flowmaster 40s on mine when I got it. Engine was a very tired low compression 400 and it was pretty loud.


Why do you think mufflers are subjective? I’ve only read opinions on restrictive exhausts and ponchos….im looking for the truths. I want to know what works and what doesn’t no bullshit….this was my dads car…and I want to make something he would cry he’d be so happy to drive…if my brothers know what im saying.


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## Jared (Apr 19, 2013)

I meant in terms of sound. If you want the best flow possible, straight through mufflers are best. I you want a quiet ride, stock are best. Seems that chambered mufflers are the loudest depending on the muffler body size and design of the baffle chambers. Engine Masters did a comparison on a very high HP engine and the chambered mufflers robbed the most power of the performance mufflers they tested (they didn't bother with a stock style). I doubt you'd notice the difference on a street engine so I'd pick based on sound.


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## 71BlueGTO (8 mo ago)

Captainfish#1 said:


> If you go the adapter route make sure it is a four hole adapter,not an open one


How come? What’s the difference in regards to how the carb operates?


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## O52 (Jan 27, 2019)

A four hole adapter maintains the dual plane manifold characteristics for fuel distribution. 
For the spacer material, wood is best at dissipating heat, followed by the phenolic/thermoplastic, then by aluminum or steel spacers


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## 71BlueGTO (8 mo ago)

Thanks Brother. I’ll keep that in mind…this is all new to me so I have alot to learn.


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