When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 77 original Quadrajet off my 77 Corvette, L48 engine..... can this carb work on a 69 big block 427 or maybe 454, whatever I build......and why not if so? The carb was rebuilt by Lars for my L48, but I now have a 406 with a Holley in the car, and have a free, well running Quadrajet available for my new project. If something needs changed,.....are the parts not available, and what would they be. I installed an electric choke, which would work on a 69 just like it did on the 77. Sorry NCRS folks,......I really don't care about orginality.
Point is.....all this talk about exact part number Quadrajets has to be about originality,.....because otherwise, its got a throttle arm, has a CFM capability.....pretty much the same, and some type of choke, and a fuel inlet location....which is same for all C3 Corvettes. So otherwise, its about calibration and jetting. Maybe some have a different base plate, as I have seen. But, really, does anyone feel like passing on what makes them so different year to year? Or maybe not.
Eventually, down the road, I will be asking Lars if he can turn my 77 Quadrajet into a good working carb for the big block in the 69.
Last edited by Shovels and Vettes; Feb 28, 2021 at 08:06 PM.
From: At my Bar drinking and wrenching in Lafayette Colorado
The significant difference between the '69 carb and the '77 carb is the fact that they're two completely different model/series carbs: The 69 (and up through 1974) Q-Jets are 4MV (divorced choke) carbs. The 1975+ carbs are M4M (integral choke) carbs. The '77 carb will not interface with the choke system on your '69 427. You'd also want to open up the IFR restrictors in the carb to use it on the big block and run the biggest primary jets you can get, which will likely be 78's along with a richer set of secondary rods (like some original '69 "AX" rods).
1969 7029215 427 390-hp Q-Jet:
Note modification to the lower part of the throttle lever to clear the 427 intake:
I know @Flyboy1958 trying to help out chrome bumper owners who are looking for Q-Jets so they can drive their cars.
@lars is there a guide that someone could follow to make these modifications? For example, if one wanted to put an M4M carb on a car that originally held a 4MV Q-jet, is there an easy way to solve the choke issue, and make the other changes? Is the simplest way way to add an electric choke (and appropriate relay and electronics) and convert it to M4ME? (Another reason 1980 was the best year for budget Corvettes).
This would make a great white paper! As long as it doesn't become a guide to butcher more Q-Jets, there are enough of those on eBay.
Last edited by Bikespace; Mar 1, 2021 at 12:00 AM.
From: At my Bar drinking and wrenching in Lafayette Colorado
There are tons of 4MV carbs in nice rebuildable condition - Rochester made about a million of them per year between 1969 and 1974, so there are still just a couple of them floating around out there for the person who wants to put in a slight amount of effort to kick one up.... There is no good reason to go through the massive amount of retrofit trouble to swap one carb model/series for another. Just use the right type carb for the application.
Lars
There are tons of 4MV carbs in nice rebuildable condition - Rochester made about a million of them per year between 1969 and 1974, so there are still just a couple of them floating around out there for the person who wants to put in a slight amount of effort to kick one up.... There is no good reason to go through the massive amount of retrofit trouble to swap one carb model/series for another. Just use the right type carb for the application.
Lars
I agree. 30-60 minutes of internet search and you will find many rebuildable candidates. Just stay away from the shiny, reflashed jobs from untrusted rebuilders. Lars' rebuilds (of your carb are the best IMO! These carbs have gone thru several generations of owners who have bent, hammered and abused prior to getting to where they are today. Few can set up a carb as well.
So how am I to know if a particular carburetor is "rebuildable" versus Lars definition of junk?
If I were looking at candidate carbs, I'd take 4-6 pictures of candidate carb and send to Lars for his opinion. With our phones having ability to take and send pictures real-time, great tech to leverage.
Short of that, use pictures that Lars has provided to compare to candidate.
OK, so a good carb is one that looks nice on the outside? I think there is more to it than that. As for configuration, I agree, I can see that. But Lars talks about all kind of hack jobs on the inside. Anyways, I think its just a crap shoot on whether you find a good carb or not. Asking an owner, or a seller, what was done to the carb on the inside is a joke. So, I guess you just buy one that looks nice, and hope Lars can make it work. Seems to me its wishful thinking, but I don't know what I expect. Thanks anyways.
That's why I think, in my case, it would be easier to convert my 77 carb to work on the big block 69. I know its a good carb because Lars already built it, and its just sitting on a shelf. I already have the electric choke installed, so now what is left, jetting, rods, throttle arm???
Last edited by Shovels and Vettes; Mar 1, 2021 at 12:10 PM.
Your most likely best bet is to find one that looks original yet not corroded badly. It really won't look that nice. A nice looking one on the outside runs a higher chance of being hacked on during a rebuild by one of the crappy shops that likes to butcher them.
OK, so a good carb is one that looks nice on the outside? I think there is more to it than that. As for configuration, I agree, I can see that. But Lars talks about all kind of hack jobs on the inside. Anyways, I think its just a crap shoot on whether you find a good carb or not. Asking an owner, or a seller, what was done to the carb on the inside is a joke. So, I guess you just buy one that looks nice, and hope Lars can make it work. Seems to me its wishful thinking, but I don't know what I expect. Thanks anyways.
That's why I think, in my case, it would be easier to convert my 77 carb to work on the big block 69. I know its a good carb because Lars already built it, and its just sitting on a shelf. I already have the electric choke installed, so now what is left, jetting, rods, throttle arm???
I would focus on finding a 'rebuildable core' with all parts present. Less shine the better. Compare to Lars' pictures above to at least determine whether it is stripped or all necessary items present.
The challenge with the carbs produced after 1974 (except for those found on the Poncho's with 455ci but they are not visually the same as the Corvette carb if I recall correctly) is they were build for SBC. Up to 1974, Corvette had big block as an option so the carb could be fitted with the correct internals. Add to that, the emissions reg's were softer.
I would try for the several part numbers that Lars mentions and do a visual. Send pictures to Lars if uncertain.
Ultimately, unless you are buying a brand new carb (ex. Holley 4150), there is risk of junk. Exception is the Edelbrock/Carter/AFB. They are junk (IMO) regardless new or used.
From: At my Bar drinking and wrenching in Lafayette Colorado
I offer a free "carb screening service." E-mail me for info. No, you generally don't want a carb that "looks nice on the outside."
This is what you're looking for: A nice, original, unmolested carb with all its parts in rebuildable condition. This is a beautiful carb with no corrosion and no damage:
Quadrajet Reality
