Quadrajet experts - please help!
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Quadrajet experts - please help!
My MPG is a shocking 7.6 MPG. So after checking timing and advance (both mechanical and vacuum) my son decided to pull the carb to see what kind of gasket I had underneath. And while it appears that I have the correct 4 hole gasket I was surprised to see the black marks on the driver-side secondary and in addition a black mark indicating some kind of bleed from the primary to secondary also on the driver's side.
Any one have any idea what is going on with the carb and/or why my MPG is so low. The car runs great, no black exhaust and while I have a 3:55 gear I have a 2004R trans. Alignment was just done, tire pressure ok. I'm thinking its gotta be in the carb.
Any help is appreciated.
Any one have any idea what is going on with the carb and/or why my MPG is so low. The car runs great, no black exhaust and while I have a 3:55 gear I have a 2004R trans. Alignment was just done, tire pressure ok. I'm thinking its gotta be in the carb.
Any help is appreciated.
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
Just a shot in the dark.....but I can't tell if there is any part of that intake that is supporting the gasket from underneath in the area you speak of. No support......no seal!!! Just a hunch.
Mark
Mark
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Interesting...but I would think all Qjets sitting on a edelbrock performer manifold would be having the same problem. But you may be on to something.
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Le Mans Master
Joined: Aug 2006
Posts: 7,411
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Using too much fuel!
Can you tell me what the carb # is mabye some one changed the rods and jets, PG.
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Race Director
Joined: May 2006
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From: Dayton, Ohio
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Fel Pro #375-1905
(from Jegs)
Insulator Gasket, 1/4" Thick, 4 Hole
Fits Holley Spread Bore, Rochester Quadrajet, Most Carter Thermoquad's
So what kind of gasket should I use? The Felpro is fiber, if I use a different material, they are thicker. Not sure how much clearance I have. Any suggestions on a gasket. And more importantly, do you think this is causing the poor MPG?
Thanks for everyones help!!!!!!!
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I'm using a Felpro 1/4 inch gasket.
Fel Pro #375-1905
(from Jegs)
Insulator Gasket, 1/4" Thick, 4 Hole
Fits Holley Spread Bore, Rochester Quadrajet, Most Carter Thermoquad's
So what kind of gasket should I use? The Felpro is fiber, if I use a different material, they are thicker. Not sure how much clearance I have. Any suggestions on a gasket. And more importantly, do you think this is causing the poor MPG?
Thanks for everyones help!!!!!!!
Fel Pro #375-1905
(from Jegs)
Insulator Gasket, 1/4" Thick, 4 Hole
Fits Holley Spread Bore, Rochester Quadrajet, Most Carter Thermoquad's
So what kind of gasket should I use? The Felpro is fiber, if I use a different material, they are thicker. Not sure how much clearance I have. Any suggestions on a gasket. And more importantly, do you think this is causing the poor MPG?
Thanks for everyones help!!!!!!!
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
Tech Contributor
Joined: Aug 1999
Posts: 14,356
Likes: 6,332
From: At my Bar drinking and wrenching in Lafayette Colorado
On your issues and questions:
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
On your issues and questions:
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
Thread Starter
Burning Brakes
Joined: Mar 1999
Posts: 1,047
Likes: 3
From: CA
On your issues and questions:
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
First, there is nothing wrong with the slight black sooting on the bottom of the carb - that's completely normal, and is not indicative of any problem.
Your base gasket should be the standard, stock, 1/4" thick open plenum gasket. The 4-hole thin gasket you're using is not causing any problem, but it's not correct, and does not work well. Use the stock 1971-1981 thick open gasket.
Poor fuel economy can be the result of a multitude of factors, and cannot be solved via e-mail or forum discussions. If timing is correct, best thing to do is to do a complete carb teardown and check its jetting specs against the correct specs for the carb. Then correct any problems with the carb (there can be dozens), set float level to .375" and do a precise blueprint setup of the carb back to spec.
Lars
