# carb



## bnreed3 (Apr 18, 2016)

just got a 69 gto judge (clone) with a '76 Trans Am 455. It doesn't have the original Qjet carb, but a Holley 600. Is this carb a good fit for this engine? I was planning to get it rebuilt or at least looked at by my local shop; however, if there is a different one that would work better I would rather put money into buying a new one over rebuilding current.


----------



## Rukee (Feb 8, 2007)

600 cfm i pretty small for a 455. You could use a larger one, but you'll lose some MPG's too.


----------



## bnreed3 (Apr 18, 2016)

This car isn't going to be for long trips, so MPG doesn't matter much to me... Plus, its an old muscle car, they aren't supposed to get good gas mileage 

What size do you guys think would best fit the 455? You think an 800 is too big?


----------



## ALKYGTO (Mar 29, 2010)

Is your carb a spread bore (larger secondarys) or square bore? Carb selection will depend on your intake manifold to a degree.....never use an adapter. That said, optimally I would want a 750 or larger carb. It wont be as snappy as that 600 if it is a conventional Holley square bore but will make up for it everywhere else. I would say if you have a spread bore manifold (stock) I would go for a Q Jet.


----------



## bnreed3 (Apr 18, 2016)

ALKYGTO said:


> Is your carb a spread bore (larger secondarys) or square bore? Carb selection will depend on your intake manifold to a degree.....never use an adapter. That said, optimally I would want a 750 or larger carb. It wont be as snappy as that 600 if it is a conventional Holley square bore but will make up for it everywhere else. I would say if you have a spread bore manifold (stock) I would go for a Q Jet.


Thanks for the reply!

It is a square bore (p# 8105B).


----------



## geeteeohguy (Feb 2, 2008)

You need an 800 cfm carb for that 455. A Quadrajet and stock intake is the way to go, and will give you more power AND better fuel economy than the current Holley.


----------



## BearGFR (Aug 25, 2008)

:agree with GeeTee. FYI the QJet's that came factory on the 455 SuperDuty engines were rated at 800cfm, so no, 800 wouldn't be too much carb. 

If you want to keep your 'square' manifold and stay with something in the Holley, Holley-like platform, then you'll be happier probably with something from AED, Quickfuel, or Demon. A friend of mine has a 455 GTO running a Demon, and the throttle response on his car is instantaneous. All you have to do is think about breathing on the go pedal, and it's gone.

Bear


----------



## bnreed3 (Apr 18, 2016)

Thanks guys! I keep hearing going QJet is the way to go. I do have the original intake manifold as well. Any good websites that sell rebuilt ones? I am not against the QJet, but sticking to square bore is the route I am leaning.


----------



## Goat Roper (Oct 28, 2014)

bnreed3 said:


> Thanks guys! I keep hearing going QJet is the way to go. I do have the original intake manifold as well. Any good websites that sell rebuilt ones? I am not against the QJet, but sticking to square bore is the route I am leaning.


I have a 7037262 late '67 QJet I just rebuilt I will sell for 500 bucks.
The mods have been done on it and it works flawlessly.


----------



## geeteeohguy (Feb 2, 2008)

The '67 is a one-year-only carb and must be used with a '67 intake. It has a special exhaust heat passage.


----------



## Goat Roper (Oct 28, 2014)

geeteeohguy said:


> The '67 is a one-year-only carb and must be used with a '67 intake. It has a special exhaust heat passage.


Thanks for the info GTOG, I didn't realize it was a one year only carb.
Maybe I should just hang onto it and keep it as a spare.
I plugged that crossover, even with the plate it was boiling this crappy gas we get out here.


----------



## geeteeohguy (Feb 2, 2008)

I would keep it, GR. '67 Q-jets for these cars are hens teeth.....


----------



## bnreed3 (Apr 18, 2016)

Thanks guys. I think I'm going with a demon 750cfm single plane. Didn't see an 800 on their website for my 455.


----------



## bnreed3 (Apr 18, 2016)

Ok, so here is what I was planning to purchase from Demon; the Street Demon 750 cfm. I was also looking at the speed demon (vacuum secondaries) but it is about double the cost. If there is a real benefit to going the speed route, please let me know. 

https://www.demoncarbs.com/1903.asp


----------



## Docjim (May 8, 2015)

I have a 67 all stock. I had a heck of a time with carbs. I tried Holley, SPeed demon (Grant), and Edelbrock. I can tune some what but the tuning it took to get these right was beyond me. I took it to several guys to tune and they all ran OK but not great. Carb hesitations, starting probs, low power for some of the symptoms. I finally contacted an engine builder that has a dyno in Minnesota. He builds engines for stock cars and has started building engines for hot rods instead. He told me that when he dyno's his engines with these carbs they all have some problems. But he said all he had to to is bolt on the Quick fuel carbs that he has laying around the engines would come to life. So I called Quick fuel technology and talked to the techs. He said that because of compressions and flow dynamics of the Pontiac engine, they are a bit harder for the guy looking for the perfect tuned carb. He told me to get the 680 CFM SS series carb and my probs would be over. No tuning!!! just bolt on and go. So I thought I would try it. Bolted it on and the 400 never ran better. Started better than ever, no hesitation any where and smooth as silk. WOW! what a difference! Never had a car run so good that was carburated. I bought one for my 56 Chevy 454 and same thing. Totally new car. This is my experience with these carbs and in fact the SPeed demon was probably the worse of the bunch. Wish I had a video posted somewhere of my 67 GTO running, it is sweet. You have the 455 so I would call Quick fuel and talk to them. Hope this helps. SS-Series Carburetor 680cfm VS SS-680-VS - Quick Fuel Technology


----------



## bnreed3 (Apr 18, 2016)

Only issue I see is that I have a single fuel inlet, many of my options are limited in this regard as the higher quality carbs feature dual inlets.


----------



## Pinion head (Jan 3, 2015)

bnreed3 said:


> Only issue I see is that I have a single fuel inlet, many of my options are limited in this regard as the higher quality carbs feature dual inlets.


"higher quality carbs feature dual inlets"...now that's funny.

Almost 2 pages of responses, and not one respondent asked you what casting cyl heads were on the '76 455 shortblock, what intake, or what the cam is being used. As the car is a Judge clone, is a steel RA tub and pan being run, any intention of running one? If the 455 still has its 6H heads, there are numerous things to be corrected to improve strong performance before blowing money on a replacement for cheap shiny entry level Holley that is on it now.


----------



## bnreed3 (Apr 18, 2016)

Pinion head said:


> "higher quality carbs feature dual inlets"...now that's funny.
> 
> Almost 2 pages of responses, and not one respondent asked you what casting cyl heads were on the '76 455 shortblock, what intake, or what the cam is being used. As the car is a Judge clone, is a steel RA tub and pan being run, any intention of running one? If the 455 still has its 6H heads, there are numerous things to be corrected to improve strong performance before blowing money on a replacement for cheap shiny entry level Holley that is on it now.


Haha. I know I am very novice! Sorry guys, very wet behind the ears. I just assumed dual inlets were better than one. I guess that was incorrect :smile3:

Honestly Pinion, I can't be sure about this. Is a mechanic able to find that information out without having to take apart the entire engine? I am assuming this 455 is a fairly stock '76 Trans Am Engine (apart from the carb and headers). Would pictures help at all? I can definitely get some engine compartment pic's. 

The more back and forth answers on carbs really makes me just want to go back to the stock QJet. I did purchase the Demon street 750cfm with vacuum secondary.

I am bringing the goat into my mechanic the week after next. I am already having him install and calibrate the new carb, look at the play in my steering (very loose from 10 to 2 oclock), replace exhaust manifold-->header gaskets with copper ones (paper ones are completely shot) and just give it a good once over. If you have any other things you'd recommend I have him look at please share. I will ask him to find out as much about the engine as possible too.

Thanks again for the helps forums.


----------

