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 1958 Viking 4400 "The Book of Thor" Read the story in the DITY 1960 Chevrolet C10 "A Family Heirloom" Follow the story in the DITY Gallery '59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane
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
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
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 ). 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! The Carburetor Shop
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 ). 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)
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)
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.
Richard Holdener 292 Series
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.
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."
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)
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.
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?
"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."
The Carter 400 was 200 CFM on the primary and 200 CFM on the secondary.
The Federal Mogul imitation 600 was 250 on the primary and 375 on the secondary (this is not a typo!), what happens when marketing issues specifications!
So subtracting 200 from the primary would yield 50 on the primary, and 375 on the secondary???
Restrictors HAVE been successfully used when engineered by ..................................engineers! Holley used restrictors on the Ford/Mercury dual quad 4000 carbs; but certainly not to this degree.
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! The Carburetor Shop
Semantics get in the way in this discussion, but Carter used "deflecters" (which also act as restrictors) for various reasons.
(1) Sheet metal deflecters were riveted to primary boosters on some small displacement engines to direct primary air flow, thus enhancing venturi air velocity.
(2) Sheet metal deflecters were added to the hot idle compensator on some Pontiac engines (secondary side) to reduce secondary CFM so that the more expensive tripower would still out-perform the standard 4-barrel engine.
Here is a picture of the Holley restrictors of which I posted previously:
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! The Carburetor Shop
My picture shows the early hot idle compensator (without wings), the later HOC with wings, and the "dummy" HOC, no compensator, just wings.
First question - yes.
The deflector cost about 35 SECONDARY CFM or approximately 6 percent airflow. The beauty of this modification is that only WOT maximum RPM is effected. Up to maximum RPM, the engine was running to its peak performance. The maximum RPM was reduced slightly. Check power ratings for 4-barrel and tripower engines 1964~1966 and you will find the tripower is rated at slightly higher HP at maybe 200 higher RPM. Now you know the rest of the story.
Second question - no.
The hot idle compensator without the "wings" was used on many other applications with automatic transmissions, including earlier Pontiac, and in fact, worked well.
The hot idle compensator with the "wings" was used on Pontiac 1964~1966 with automatic transmission.
The "dummy" hot idle compensator (no compensator, just the "wings") with "wings" was used on Pontiac 1964~1966 with standard transmissions.
As a general rule, hot idle compensation was not used with standard transmissions.
So - to improve performance on automatic transmissioned cars, replace the winged HOC with the non-winged HOC.
To improve performance on the standard transmissioned cars, just remove the dummy. The HOC passage is not machined on the standard transmissioned carbs.
Later, Pontiac pulled a similiar trick (limited butterfly movement) with Q-Jets on Firebirds, so the 10 pounds / HP formula was not violated.
Marketing departments played games.
Maybe a better example (certainly one more widely known) of marketing games (much later) was tire shaving for cars used in magazine tests (and Chevrolet got caught ). Look for a "Road & Track" article in the 1980's (I think) entitled "Can we build one for you?"
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! The Carburetor Shop
A magazine reported around 1970 that the 400 in the GTO had 10 (?) more HP than the same engine in the Firebird because the secondary air valve stop prevented it from opening fully. The "1 hp per 10 lbs" GM rule (Corvette being the exception). I used to love de-smogging QJ, so much improvement for an hour's work!
The attached picture (new clone vs original AFB converted) is of different CFM carburetors but the primary design change by the clone maker is a curiosity. It could simply be motivated by "cheaper to make" reason more so that any improvement in performance. Anyway, I'm sure the add-on conversion came about because "this is the way the clone maker did it" whether good or bad. My first thought was of air flow turbulence caused by the restrictors so I discounted it but I hadn't considered that at lower RPMs, it may not have as much of an affect. The design could well be poor at WOT especially on a racing V8. Sorry for distracting the discussion.
"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."
To again quote Jerry: "It is a solution (my comment - maybe it is a solution) looking for a problem.".
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! The Carburetor Shop
Dongray Guess I will chime in I must be the only one in America that runs propane. That 9.5 to 1 292 cammed engine would run good on LPG,Had a 11.25 to1 327 in my service truck for 12 years ran fine. Also still have a 235 with dual propane carbs and fenton split exhaust worked good. You can buy the parts new off Amazon,just need a good full service propane dealer to help with a few things !!
A magazine reported around 1970 that the 400 in the GTO had 10 (?) more HP than the same engine in the Firebird because the secondary air valve stop prevented it from opening fully. The "1 hp per 10 lbs" GM rule (Corvette being the exception). I used to love de-smogging QJ, so much improvement for an hour's work!
Tell me more about de-smogging a QJ….what it entails.
). It took 5k (time) to get the Offy intake, Offy was backlogged even then.