Quadrajet interchangeability - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crm318 · 01-12-2010, 06:01 PM

I found a quadrajet that I found on a 1979 Cadillac 425 in my grandfathers garage. I took the carb off, disassembled it and let it soak in degreaser. I once heard that the 1979-1980 quadrajets were the best designed of all the quadrajets. Is this true? I think that the throttle shafts on this carb my be a little worn. Could I put the baseplate of my current (5 year old) quadrajet on the later model body and airhorn? I know that I will have to tinker with the needle and jets also. What do yall think?

68gmsee · 01-12-2010, 06:35 PM

My first guess is that it won't interchange. I've got 3 of them in my garage and all are different. One is for a 69 Chevy, another I got from a 77 Chevy and another off ebay vingage 80 something.

Quadrajets were made for many different vehicles and each had their own quirks, not to mention the different epa requirements of each state.

But, what the hey, their easy enough to dismantle. They look like a mechanical nightmare but after doing a little reading and taking them apart a few times it gets easier.

crm318 · 01-12-2010, 10:27 PM

I forgot to mention that I have built over 15 of these in the past. They look complex, but i think they are easier than some holleys I have built. The engine im putting it on can handle the added fuel (if not I can lean it out). My main question is if the 1979 design is better than the one I have now. This carb is an 800 cfm unit according to the provisions in the primary bores. My current carb is from a 1973 corvette with a manual transmission (I know everyone says corvette this or that but the casting numbers check out). Im just looking for the best efficiency and economy in design.

dan42 · 01-12-2010, 11:02 PM

I had heard that about the '79 and '80 quads as well, although I'm not sure why they would be better than any other year. I have an '80 on my '67 and it really runs nice, but if it hasn't been started for a couple of days, it's a little stubborn. I think that has more to do with the rebuild though.

crm318 · 01-12-2010, 11:38 PM

Well, from what I have heard, that is due to the well plugs that eventually drain the fuel bowl from a small leaking. This is a common problem on most all quadrajets.

01-12-2010, 06:01 PM	#1
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Quadrajet interchangeability I found a quadrajet that I found on a 1979 Cadillac 425 in my grandfathers garage. I took the carb off, disassembled it and let it soak in degreaser. I once heard that the 1979-1980 quadrajets were the best designed of all the quadrajets. Is this true? I think that the throttle shafts on this carb my be a little worn. Could I put the baseplate of my current (5 year old) quadrajet on the later model body and airhorn? I know that I will have to tinker with the needle and jets also. What do yall think? __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies

01-12-2010, 06:35 PM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Quadrajet interchangeability My first guess is that it won't interchange. I've got 3 of them in my garage and all are different. One is for a 69 Chevy, another I got from a 77 Chevy and another off ebay vingage 80 something. Quadrajets were made for many different vehicles and each had their own quirks, not to mention the different epa requirements of each state. But, what the hey, their easy enough to dismantle. They look like a mechanical nightmare but after doing a little reading and taking them apart a few times it gets easier.

01-12-2010, 10:27 PM	#3
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Quadrajet interchangeability I forgot to mention that I have built over 15 of these in the past. They look complex, but i think they are easier than some holleys I have built. The engine im putting it on can handle the added fuel (if not I can lean it out). My main question is if the 1979 design is better than the one I have now. This carb is an 800 cfm unit according to the provisions in the primary bores. My current carb is from a 1973 corvette with a manual transmission (I know everyone says corvette this or that but the casting numbers check out). Im just looking for the best efficiency and economy in design. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies Last edited by crm318; 01-12-2010 at 10:43 PM.

01-12-2010, 11:02 PM	#4
dan42 Registered User Join Date: Feb 2007 Location: Cali Central Coast Posts: 5,191	Re: Quadrajet interchangeability I had heard that about the '79 and '80 quads as well, although I'm not sure why they would be better than any other year. I have an '80 on my '67 and it really runs nice, but if it hasn't been started for a couple of days, it's a little stubborn. I think that has more to do with the rebuild though. __________________ '67 SWB Fleetside ZZ4/350/Tremec 5-speed/4link/Scott's IFS - and fun as heck! SOLD Click here to support the board Philippians 4: 6-7

01-12-2010, 11:38 PM	#5
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Quadrajet interchangeability Well, from what I have heard, that is due to the well plugs that eventually drain the fuel bowl from a small leaking. This is a common problem on most all quadrajets. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies



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