Current GM Q-jet Rules

[Hacksaw]

Hey Oldschool: I was told by a very reputable QJ carb guy that he did not see any performance difference between an Edelbrock or GM 207 carb and he preferred the Edelbrock because usually they were nicer cores to start with. Good time to check the classsracer parts section. Good deal there on what you need.

[Dwight Southerland]

Part of the distinction with the Qjet carbs is that all the GM carbs were manufactured by Rochester, which means they are the same make and model. The Edelbrock replacements are listed in the Accepted Products publication under Carburetors along with Edelbrock's AFB replacements and the QuickFuel replacements. They are listed distinctly because they are different manufacturers (make). No need to list all the carbs by the OEM manufacturer.

[ss3011]

Carter made them for GM back in the mid 70's too .

[Rich Biebel]

Originally Posted by ss3011

Carter made them for GM back in the mid 70's too .

Yes and they were real poor casting quality IIRC and not colored like a Rochester....Same color as an AFB....

I did not like trying to rebuild one of those.

Rebuilding carbs was a real common job in my gas station days.

[oldskool]

Originally Posted by Hacksaw

Hey Oldschool: I was told by a very reputable QJ carb guy that he did not see any performance difference between an Edelbrock or GM 207 carb and he preferred the Edelbrock because usually they were nicer cores to start with. Good time to check the classsracer parts section. Good deal there on what you need.

Yeah, they are quite a few years newer than the GM Q-jets. That alone should mean that a larger percentage of 'em are in better shape.

And thanks for the heads-up ! But I already have a couple of E-Q's. And there are always several for sale on Ebay.

Also, have a small stash of GM Q-jets, and access to lots more.


" Carter made them for GM back in the mid 70's too. "

Yeah, Carter made LOTS of Q-jets, in the '60's & '70's. Their name is cast into driver side of the main body. " MFG. BY CARTER CARBURETOR FOR GMC ".

[oldskool]

While we're on the subject, I've got more questions.

(1) What is a ballpark figure that one of the good class car Q-jet builders would charge to build a Stocker type unit, using my core ?

(2) Aprox how much quicker is a Q-jet which is built by one of the top class racer guys, as compared to a good average street/strip or bracket race build ? Just wondering if it would be worth the extra $$, if all you wanted to do was just be able to run slightly under your index, rather than building to win all your heads-up races. (Not looking for any good buys on ready to race carbs--just gathering facts.)

(3) In pics I've seen, it shows the choke plate still in, Stock & SS. So, is it a rule that the choke plate must remain ?

(4) Haven't seen any pics of the Stock & SS cars running an air cleaner. So, aprox how much power is lost by using a good air cleaner set-up ? I assume there have been lots of dyno and track tests for this, thru the years.

[Bob Mulry]

The statement "stock inlet location" was included in my 2003 NHRA Rulebook......

The statement was no in my 2005 NHRA Rulebook....

I can't find my 2004 rulebook...

So the inlet location requirement was removed in 2004 or 2005.....

Because B-O-P and Cadillac that came from the factory with a front inlet now could run a side inlet carburetor.....

Edelbrock only sold side inlet carburetors...This rule change greatly increased their market......

The oldest rulebook that I can easily put my hands on is 1995 and at that time it was restricted to the size, inlet location and external appearance. Computer carbs could be replaced with non-computer with the same size bores and venturi...

Hope this helps,
Bob

[Mark Yacavone]

Originally Posted by Bob Mulry

The statement "stock inlet location" was included in my 2003 NHRA Rulebook......

The statement was no in my 2005 NHRA Rulebook....

I can't find my 2004 rulebook...

So the inlet location requirement was removed in 2004 or 2005.....

Because B-O-P and Cadillac that came from the factory with a front inlet now could run a side inlet carburetor.....

Edelbrock only sold side inlet carburetors...This rule change greatly increased their market......

The oldest rulebook that I can easily put my hands on is 1995 and at that time it was restricted to the size, inlet location and external appearance. Computer carbs could be replaced with non-computer with the same size bores and venturi...

Hope this helps,
Bob

Note..The Caddy was side inlet.The A/C compressor was in the middle front..
Carry on, Bobbo

[Bob Mulry]

Originally Posted by Mark Yacavone

Note..The Caddy was side inlet.The A/C compressor was in the middle front..
Carry on, Bobbo

My bad............................

[oldskool]

Originally Posted by Bob Mulry

The statement "stock inlet location" was included in my 2003 NHRA Rulebook......

The statement was no in my 2005 NHRA Rulebook....

I can't find my 2004 rulebook...

So the inlet location requirement was removed in 2004 or 2005.....

Because B-O-P and Cadillac that came from the factory with a front inlet now could run a side inlet carburetor.....

Edelbrock only sold side inlet carburetors...This rule change greatly increased their market......

The oldest rulebook that I can easily put my hands on is 1995 and at that time it was restricted to the size, inlet location and external appearance. Computer carbs could be replaced with non-computer with the same size bores and venturi...

Hope this helps,
Bob

Yeah, this is some good info ! Thanks !

So, if this info is correct, that means the Edelbrock Q-jets were not legal 'til after production of them had stopped.

"...1995...at that time it was restricted to the size, inlet location and external appearance..."

That "external appearance" deal is very interesting. I wonder how strict they were about enforcing that rule ? EXACTLY WHAT about the "external appearance" would make a carb not legal ?

Being a Pontiac guy, there are some things that come to mind. The biggest difference I can think of is the big "smokestack" vent, which began with the '70 Calif models, and continued thru '79. So, the questions that come to mind are:

(1) Were these big vent models legal on '67-'69 model Pontiacs, and other BOP engines ?

(2) And there is the question of the opposite situation. How about using a small vent model on a '71-'79 Pontiac, which came with the big vent ?

(3) And, the big vent models looked very similar from '70-'74. But, later models had the vent in a slightly different place, and there were tops with 2 slightly different looks, in the '77-'79 years. So, how close would the appearance have to be ?

(4) And then there were the slashed vent models. Some '60's & '70's Pontiac & Buick models had slashed vents, as compared the the flat top vents, on most models. The SD455 even had a large slashed vent. The slashed vent definitely presents a different appearance. Was it enuff of a difference ?

(5) Another thing that comes to mind is the difference in the appearance of the throttle levers. Different year Pontiac levers were quite different. And other brands, such as Buicks, had a very different looking lever, with a spring which mounted toward the front, on the idle solenoid bracket, whereas most Pontiac springs were attached to the rear, on the throttle cable bracket. So, a Buick carb would look quite different than a Pontiac carb, on the driver side.

(6) Then there is the choke mount type, and choke pull-off type, size and location. All these items presented several different looks, on the different models. So, this would present a different "appearance". The question again is: just how picky were the tech guys, on this "external appearance" rule ?

So, for you guys who were racing back in those days, how do you remember the Q-jet tech details ?

I remember going to a div 4 race, in '75. I took 2 cars. We didn't even get to unload 'em. Wesley saw us & came over to take a look. He named off a bunch of little nit pickin items that I'd have to fix, before he'd even take a closer look. That was my introduction to NHRA & Wesley. There was no way I could fix all those items, away from the shop, so we just watched the race, & went home.

We'd ran all season at several small local tracks, winning quite a few races. There was little to almost no tech. And the tech guys were all Chevy guys, so they knew nothing about a Pontiac. One car did get DQ'd at one race. The boys got tired of gettin beat by a Pontiac with a female driver & protested the car. The tech guys didn't find anything wrong with the engine, so they weighed the car. It came up just a very few lbs light. I'd never even weighed it. Since it still had most all the street equipment, I assumed it was a little over weight. Anyhow, I put a spare tire in the trunk, & she continued winning.

Anyhow, I've always found the variations in Q-jets very interesting. Stuff like an OHC inline six Q-jet, a Q-jet equipped 429 CJ Ford, a straight inlet 454 truck Q-jet, and even a Dodge pickup Q-jet.

http://429mustangcougarinfo.50megs.com/new_page_6.htm