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Re: Carburetor Selection for modified 292
Dongray #1429154 Thu Nov 04 2021 11:38 AM
Joined: Mar 2007
Posts: 1,609
T
Crusty Old Sarge
There are a number of places that offer rebuild services for GM Quadrajet carburetors. Finding a good rebuildable core may be an issue thought. I personally love a Quadrajet, when they are right the perform great, when they're bad they are basically junk. Not many people know or understand enough about these carbs to complete a good rebuild, those that do are getting more scarce by the day. I have only know one person who could do a correct rebuild and make it perform as it should , sadly he passed on a number of years ago.

As Jerry stated, find one for a 283 or 305 and you should be in the ball park for CFM. Don't worry to much about the secondary's as the primary side is where you spend most of your throttle time.

A quick search for Quadrajet rebuilder brought up a number of companies, some with decent reviews. Good luck.


Craig

Come, Bleed or Blister something has got to give!!!
59' Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
Re: Carburetor Selection for modified 292
Dongray #1429165 Thu Nov 04 2021 01:51 PM
Joined: Feb 2004
Posts: 24,250
H
Kettle Custodian (pot stirrer)
A 283 QJ carb would be about as scarce as a chicken with lips. There was a Pontiac 250 OHC six with a QJ, but those carbs are extremely hard to find and expensive when they're located. A 292 with a little bit of overbore will be right in the ballpark for a 305 carb.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

WAG MORE- - - - - -BARK LESS!
Re: Carburetor Selection for modified 292
Dongray #1429181 Thu Nov 04 2021 04:31 PM
Joined: Nov 2002
Posts: 2,347
C
Carburetion specialist
Originally Posted by DoubleDingo
I think I have one of these 9400's. I took it off my truck because it lost adjustment nearly weekly, drove me nuts. I was a quick starter, though, even after sitting a few days or even when the weather was cold the engine would fire up immediately with a tap of the key.

Edit: The Carter was on a 305-307-350, I don't think it's a 350 because the engine is a dog, but it did lose adjustment quickly, and I don't know why unless they are prone to losing adjustment like that.

Somehow, this post eluded me, and I just read it.

No carburetor (even a Rochester B) if in reasonable condition, and properly adjusted, should need readjustment weekly!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I bought my van used, with approximately 75k miles. I drove it for maybe 5k, and hated both power and fuel economy from the Holley. (Maybe if more of the fuel from a Holley actually went into the engine, they would get better fuel economy wink ). It took 5k (time) to get the Offy intake, Offy was backlogged even then.

I installed the Offy intake, and the 9400 at approximately 80k. It was UNTOUCHED until I removed it at 460k when the body rusted out for the third time from Missouri salty winters, and I scrapped the van.

Jon


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify
If you truly believe "one size fits all" try walking a mile in your spouse's shoes!
[image]http://www.thecarburetorshop.com/Avatar.jpg[/image]
Re: Carburetor Selection for modified 292
carbking #1429184 Thu Nov 04 2021 04:59 PM
Joined: Dec 2015
Posts: 535
D
Unconventional Thinker
Originally Posted by carbking
Somehow, this post eluded me, and I just read it.

No carburetor (even a Rochester B) if in reasonable condition, and properly adjusted, should need readjustment weekly!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I bought my van used, with approximately 75k miles. I drove it for maybe 5k, and hated both power and fuel economy from the Holley. (Maybe if more of the fuel from a Holley actually went into the engine, they would get better fuel economy wink ). It took 5k (time) to get the Offy intake, Offy was backlogged even then.

I installed the Offy intake, and the 9400 at approximately 80k. It was UNTOUCHED until I removed it at 460k when the body rusted out for the third time from Missouri salty winters, and I scrapped the van.

Jon

That's what I thought, too. When I bought the truck it ran good, started easily, and had some nuances/quirks that I had never encountered on any old truck, but I figured I could fix them as time went on.

Having never seen or heard of a Carter AFB (I grew up in a small town, had little to no money, before the internet, no speed shop or the like, and nobody in our school was hopping-up their cars with speed parts), so I didn't know anything about them, and not wanting to deal with it anymore, I grabbed my spreadbore intake and unused quadrajet, and swapped them on. I did so because I am familiar with quadrajets, and that particular Carter, like I stated needed adjustment weekly if I drove the truck daily. I don't know if it is worn out internally and/or externally, but I am curious about it now that I have read your success story with the Carter in your van. I'll dig it out and get some photos to share, to see if it truly is a 9400, or worth my time.


Shane

Shane's Toys...
2007 Forester XT Limited (2nd Owner)
1991 Cherokee Laredo (2nd Owner)
1981 Chevy 3/4 Ton Fleetside 8,600 Camper Special (3rd Owner)
1965 Chevy 3/4 Ton Fleetside (3rd Owner)
Re: Carburetor Selection for modified 292
Dongray #1429219 Thu Nov 04 2021 08:56 PM
Joined: Dec 2015
Posts: 535
D
Unconventional Thinker
Well Jon, I don't have a good Carter. I dug it out during lunch, and it is a 9635sa, and while I ate I did a search and found a discussion you had with a guy named Jerry on Chevy Talk, and basically you said the 9635sa was not a good one. Maybe that is why I couldn't ever keep it running good.

Edit: I'll post some pics of it if you want me to, but it's probably pointless, as this is too big of a carb, and not a desirable one at that.


Shane

Shane's Toys...
2007 Forester XT Limited (2nd Owner)
1991 Cherokee Laredo (2nd Owner)
1981 Chevy 3/4 Ton Fleetside 8,600 Camper Special (3rd Owner)
1965 Chevy 3/4 Ton Fleetside (3rd Owner)
Re: Carburetor Selection for modified 292
Dongray #1429227 Thu Nov 04 2021 09:58 PM
Joined: Apr 2016
Posts: 690
M
'Bolter
Originally Posted by DoubleDingo
Jon and Panic, thanks for all the information and sorry for not being able to respond sooner but I don't get much time lately. I do have to say it is a lot digest considering I have never worked on a carb and only limited amount on a couple engine rebuilds with my dad many years ago.
I think a major point that was made and finally sunk in on me was the amount of time just driving normally 95% vs amount of time wanting it to perform. That being said I know this engine won't sip gas and am willing to suffer some for fun every now and then. Although filling up at the pump today for my daily took a chunk out of my wallet!
I think what got me considering larger carbs were first the Holley site where you punch in the size of your engine size and if it is stock, mildly modified or highly modified and it would consisently spit out 470- 650? when I put in mildly modified. Then there were videos of folk doing dyno runs on 250s and 292 saying 500 was insufficient for the 250 (first video) and I think they used a 750 on a 292 that was somewhat modified being built for turbo (second video). I really wish Richard Holdener would have finished his series on a 292. He did compare a two barrel vs a very large 4 barrel at the time and I think the 4 barrel was almost equivalent with the two barrel but the engine and head were stock if I recall correctly. Unfortunately the video series was never completed. I would have been great see how it performed with multiple carbs and intake manifolds.

https://www.youtube.com/watch?v=1p3-cAJrLCw

https://www.youtube.com/watch?v=hXp5dnAEjNU

Richard Holdener 292 Series
https://www.youtube.com/watch?v=hXp5dnAEjNU


I am not going to argue the math or physics and the excellent explanations provided for a smaller carburetor in this forum but you can see where this confusion stems from when watching these builds. I mean based on everyones calculations on this page anything over 450-500 is a waist. I understand that there are a lot of variables but other than the video of the 250 the other two builds had less done my build.

So is there anyone that makes a decent Q jet carb that you might recommend in the size Im looking for? I would prefer one that is easier for the newbie to work with if that is at all possible.


I offered to send him a full race iron head to test and he didn't take me up on it.


Old enough to know better, too young to resist.
Re: Carburetor Selection for modified 292
Dongray #1429351 Sat Nov 06 2021 01:32 AM
Joined: Mar 2010
Posts: 1,071
B
Curmudgeon
The previous statement "basically you said the 9635sa was not a good one" caught my eye.

Not trying to steal thunder from one of Jon's older forum messages, I recall:

The 9635sa is a CLONE of the great originally Carter-made 9635s.
They are not the same carburetor.
This also appiles to the 9636sa and 9637sa (Chrysler and Ford respectively).
Carter went out business around 1985 and so began the clones.


In searching for member experiences of the Carter YF (my own curiosity) in other forums and I couldn't help but notice statements that are common with the Stovebolt forum and this discussion. Mainly the Ford Six (240 and 300) and Jeep Six (258) forums. Repeating words like "torque engines", low VE at higher RPMs (compared to V8) and members/owners tending to overcarburate. Please don't shoot the messenger. Sound familiar?

Now back to 1985 when fuel injection started taking business away from the carburetor companies, the dog-eat-dog competition amongst the remaining companies lead to the "Marketing Department". Their goal is to create specifications that snag the average buyer. Fuel injection is superior so why waste money on a "Design Engineering Department" to improve the function of the carburetor. Just clone what was made in the past and find ways to improve manufacturing ROI (make more profit with less cost). The last four sentences are my words but is it not typical of the history of busniesses in the USA?

So the new carburetors made today, regrdless of name branding, are designed with a "vortex" for our dollars (credit card)? Choose carefully.


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."
Re: Carburetor Selection for modified 292
buoymaker #1429553 Mon Nov 08 2021 06:06 PM
Joined: Dec 2015
Posts: 535
D
Unconventional Thinker
Originally Posted by buoymaker
The previous statement "basically you said the 9635sa was not a good one" caught my eye.

Not trying to steal thunder from one of Jon's older forum messages, I recall:

The 9635sa is a CLONE of the great originally Carter-made 9635s.
They are not the same carburetor.
This also appiles to the 9636sa and 9637sa (Chrysler and Ford respectively).
Carter went out business around 1985 and so began the clones.


In searching for member experiences of the Carter YF (my own curiosity) in other forums and I couldn't help but notice statements that are common with the Stovebolt forum and this discussion. Mainly the Ford Six (240 and 300) and Jeep Six (258) forums. Repeating words like "torque engines", low VE at higher RPMs (compared to V8) and members/owners tending to overcarburate. Please don't shoot the messenger. Sound familiar?

Now back to 1985 when fuel injection started taking business away from the carburetor companies, the dog-eat-dog competition amongst the remaining companies lead to the "Marketing Department". Their goal is to create specifications that snag the average buyer. Fuel injection is superior so why waste money on a "Design Engineering Department" to improve the function of the carburetor. Just clone what was made in the past and find ways to improve manufacturing ROI (make more profit with less cost). The last four sentences are my words but is it not typical of the history of busniesses in the USA?

So the new carburetors made today, regrdless of name branding, are designed with a "vortex" for our dollars (credit card)? Choose carefully.

This 9635sa came with the truck when I bought it in 2015. When Jon mentioned he had great success using a Carter AFB 9400 on his econline's 300, and me not knowing a thing about Carter's, I thought I had a jewel in the rough, but it was just a turd. Before lunch on Friday I did some searching to see what a Carter AFB 9400 may look like, so I could see if mine was worth the effort, and then I read the history of Carter. Once I dug it out, I saw it was different immediately, and then after a quick search of 9635sa, it was clear that AFB in my possession was not worth my time for this engine or any other for that matter. Of course it is way too much carburetor for the modified 292, but as I mentioned previously, it needed to be adjusted nearly once a week. In my case I was not out any money for the turd AFB, and won't be, as it will not see another engine unless I sell it or give it to someone. But it would have to be someone I don't expect to see again, because I wouldn't sell or give a turd to a friend...lol...

Side note, I recently bought a "NEW" quadrajet for my '81 C20, and upon receiving it, it looks great, but it is clear it is not a quadrajet. It may look like one, but I highly doubt it will perform like one, and there won't be replacement parts available, etc, so it is going back. I will take my chance on a rebuilt Rochester. Clones will never be as good as the originals, and it is clear that both clones I have in my possession, the AFB and the Quadrajet, will never come close to being as good as the originals.

Before logging in this morning, I saw someone bought a 9400 AFB on ebay. I guess they are still out there, but very rare, and probably very expensive when they become available.


Shane

Shane's Toys...
2007 Forester XT Limited (2nd Owner)
1991 Cherokee Laredo (2nd Owner)
1981 Chevy 3/4 Ton Fleetside 8,600 Camper Special (3rd Owner)
1965 Chevy 3/4 Ton Fleetside (3rd Owner)
Re: Carburetor Selection for modified 292
Dongray #1429557 Mon Nov 08 2021 06:45 PM
Joined: Dec 2008
Posts: 1,707
P
'Bolter
The effect of a carburetor larger than needed (more rated CFM than the calculation)?
1. if the primaries are about the right size, the idle, response, mileage, and part throttle will be the same as a smaller carburetor with the same size primaries.
2. if the primaries are too large, response will be soft, some delay on tip-in, lower mileage, etc.
3. if only the secondaries are too large, a vacuum secondary (or secondary air valve, such as AFB, AVS, QuadraJet, ThermoQuad) will simply not open fully, so the CFM delivery will be less than the rating.
4. if mechanical secondaries, the WOT vacuum will fall below the factory calibration rating at 1.5" Hg, and the A:F delivery curve (BFSC, brake specific fuel consumption) will not be a good match for your engine, and may deliver less power than the correct size.

Biggest reason not to use a QJ? Not many good manifolds for the weird base flange pattern and entrance shape.
I've worked on them for 50 years on Buick 350, 455, and V6 turbo, Cadillac 425, always good results with minor adjustments.

Re: Carburetor Selection for modified 292
Dongray #1429596 Tue Nov 09 2021 02:08 AM
Joined: Mar 2010
Posts: 1,071
B
Curmudgeon
Panic you probably know more about this that I do.
Adding restrictors and rejetting to reduce the CFM.
Is this just smoke and mirrors or does it have some merit?

Attached Files
600 to 400.jpg (40.16 KB, 68 downloads)

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."
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