Qusdrajet rebuild?
Thread Starter
Instructor
Joined: Jan 2018
Posts: 229
Likes: 31
From: Finger Lakes area NY
Qusdrajet rebuild?
This is my first Corvette... 68 BB Convt...
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Last edited by Tom_K; Sep 19, 2018 at 04:54 PM. Reason: correct error in post
Burning Brakes
Joined: Nov 2011
Posts: 1,170
Likes: 201
From: Willoughby Ohio
Cliff Ruggles has an excellent book on Quadra-jets if you want to try it yourself.
If you are not sure you want to do it look up Lars on this forum. He also has papers you can
download to help you if you are interested.
(Edit)
If you are not sure you want to do it look up Lars on this forum. He also has papers you can
download to help you if you are interested.
(Edit)
Last edited by vettebuyer6369; Sep 19, 2018 at 07:23 PM. Reason: remove NSV promotion
Safety Car
Joined: Sep 2005
Posts: 4,232
Likes: 645
From: Orange County Ca
Yes, get the book (or maybe available on line?). This carb is as simple or as intricate as you want. There are numerous adjustments that you may or may not need and there are a few tricks for reassembly. I'm sure that there are different brands of rebuild kits available so you'd want to research which is best or most complete. Make sure that the float is compatible with modern gasohol.
Melting Slicks
Joined: May 2007
Posts: 2,415
Likes: 154
This is my first Corvette... 68 BB Convt...
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Burning Brakes
Joined: Mar 2016
Posts: 1,008
Likes: 163
This is my first Corvette... 68 BB Convt...
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Appears the float bowl is leaking or draining (not leaking from carb onto manifold but draining back to tank?)
When the car is parked for a few days, I have to crank it for a while to allow the fuel pump to fill the bowl. It then fires up and runs well.
I am thinking a basic rebuild of the carb is in order. But... I am a Holley guy and think "Holley"
I have never touched a Q-jet carb...
Is this a simple rebuild or is there more to it? Is there anything unusual about these carbs.
Is this a simple DIY project?
Thanks Tom
Melting Slicks
Joined: May 2007
Posts: 2,415
Likes: 154
Went through the same thing with my float bowl draining after a day or two. Filter with a check valve didn't do anything for me. Ended up being float bowl well plugs seeping. If you search on the forum you will find the walkthrough, but basically you drill out the solder plugs and tap them. Then thread in a plug coated in JB weld to seal it up. After that, my car started up first try even after sitting for days!
Burning Brakes
Joined: Mar 2016
Posts: 1,008
Likes: 163
Well I can attest to the fact that my well plugs were leaking. I pulled the Qjet off the motor and set it up on my workbench with the float bowl full of fuel. Made sure everything was clean and dry. Came back a few hours later and the well plugs were slightly damp. Dried them off again just to be doubly sure, and a few hours later they were slightly wet with fuel again. So mine were DEFINITELY leaking. Hence drilling, tapping, and inserting a threaded plug. The JB weld was to be doubly sure that it couldn't leak past the threads. I definitely didn't want to do this job, put it on my engine and have the same problem as before without knowing why just because I skipped sealing my threads thoroughly.
Race Director
Joined: Mar 2017
Posts: 11,960
Likes: 4,518
From: Virginia
I haven't done it yet on my 79, but I suspect that I'll find the same weeping plugs when I pull it apart.
Short of a rebuild, try the other things first. The check valve fuel filter helped, but didnt fix the problem for me.
Short of a rebuild, try the other things first. The check valve fuel filter helped, but didnt fix the problem for me.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Burning Brakes
Joined: Mar 2016
Posts: 1,008
Likes: 163
You are both correct. The leaking well plugs are a rarity - very seldom do you actually see this problem. In the 800+ carbs I have rebuilt over the years, I can count the number of leaking plugs on one hand. When you do see it, it is usually on the early ('66 - 70) carbs. I've never seen it on the '71+ carbs. The test method and repair process is exactly as mobird describes: Fill the bowl with fuel and set the carb up on your workbench so you can observe the bottom. If it leaks, you cannot repair it by just "smearing" the plugs with JBWeld, as most rebuilders do. That exercise is pointless. The plugs must be drilled and tapped, and threaded inserts, coated with JBWeld, must be installed.
Lars
Lars
Melting Slicks
Joined: May 2007
Posts: 2,415
Likes: 154
You are both correct. The leaking well plugs are a rarity - very seldom do you actually see this problem. In the 800+ carbs I have rebuilt over the years, I can count the number of leaking plugs on one hand. When you do see it, it is usually on the early ('66 - 70) carbs. I've never seen it on the '71+ carbs. The test method and repair process is exactly as mobird describes: Fill the bowl with fuel and set the carb up on your workbench so you can observe the bottom. If it leaks, you cannot repair it by just "smearing" the plugs with JBWeld, as most rebuilders do. That exercise is pointless. The plugs must be drilled and tapped, and threaded inserts, coated with JBWeld, must be installed.
Lars
Lars
Last edited by PAmotorman; Sep 21, 2018 at 10:35 PM.
Heel & Toe
Joined: Mar 2017
Posts: 19
Likes: 0
be careful with these check valves because I had one on my quadrajet and the ethanol in the gas made the rubber around the check valve expand and starve the engine of gas. took me two weeks and a 100 mile tow to figure it out. I took the check valve out and if it sits a couple hours just press the gas pedal twice and it starts right up. with that being said I have been told the qjet is the 'best' for our setup on vettes. a lot of guys who know other brands don't care for it because of the intricacies of the qjet but from what I have been told since I am also a noob is that the qjet is well worth learning and understanding how to properly rebuild and tune it.
Advanced
Joined: Jun 2018
Posts: 76
Likes: 1
From: Glenolden Pa.
Well how about that, for decades the OE E4ME on my 1981 would be dry after a week of sitting...I just thought the gas evaporated out of it...(I hate Q-Jets, give me a Holly 4150 any day, so easy to work-on and tune)
With that being said, just yesterday I dropped off a Q-Jet that was under my bench for decades, it was on a BBC Truck (1978-79) for a full rebuild and tested on an engine before handed back to me.
I'm removing the ECM controlled Q-Jet and ECM controlled distributor...I've had enough of it and acting up.
With that being said, just yesterday I dropped off a Q-Jet that was under my bench for decades, it was on a BBC Truck (1978-79) for a full rebuild and tested on an engine before handed back to me.
I'm removing the ECM controlled Q-Jet and ECM controlled distributor...I've had enough of it and acting up.