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Username Post: Quadrajet lean out        (Topic#364649)
Posts: 5

Reg: 03-08-21
03-18-21 10:07 AM - Post#2816364    

'70 Chevy C/10, 350 w/Quadrajet. Here goes: EVERYTHING,from tank up to the carb has been replaced. Carb has been rebuilt. Here is what it does: after running at idle, the see through fuel filter will empty and engine will die. After a fairly sharp turn, maybe 30 yards later engine will sputter and die. float height at 1/8", no contact with anything on the sides of the float. Lift clip for needle in central location on float (not trapped in openings left or right.) Fuel pump is delivering 14 PSI, but apparently closed needle will not permit fuel entry to float bowls. Have been unable to locate anything that would indicate what the problem might be.


"6th Year" Gold Supporting Member
Posts: 1034
Age: 63
Loc: New Westminster BC
Reg: 09-25-13
03-18-21 12:32 PM - Post#2816374    
    In response to jeff32668

Is that a mechanical fuel pump or electric? Mechanical should only be about 7-10 PSI if I read correctly.
I don't know what too high a PSI does to a quadrajet but it seems high.

Steve Duncan
66 Impala 2dr Coupe
Not sure of color yet
work in progress

Mel Foye 
*VIP* Original Founding Member Group
Posts: 5279
Mel Foye
Reg: 09-29-00
03-18-21 09:14 PM - Post#2816400    
    In response to jeff32668

5# PSI is a good ballpark for a Quad. Is the 1/8 for upward gap on floats?

Senior Member
Posts: 1540
Loc: Missouri
Reg: 06-14-03
03-20-21 04:54 AM - Post#2816443    
    In response to Mel Foye

14 psi at the carburetor should shower the engine with gasoline!!!!!!!!!!!!!!!!! !!!!

Try disconnecting the fuel line right at the carburetor, and inserting a fuel pressure gauge there.


Good carburetion is fuelish hot air!

The most expensive carburetor you will ever the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!

Posts: 5

Reg: 03-08-21
08-09-21 07:21 AM - Post#2824792    
    In response to carbking

Ok, the pump is mechanical. I found that the phenolic heat shield block wasn't in. Installed that. If the engine idles you can literally watch the fuel filter empty out. I'm wondering if it's a case of vapor lock? With the alcohol in the gas these days, perhaps it's boiling off. I'm wondering if an electric fuel pump would be the cure? I haven't really seen a case of vapor lock in forty years.

Frequent Contributor
Posts: 2367

Loc: Lake George, NY
Reg: 11-11-15
08-09-21 01:13 PM - Post#2824821    
    In response to jeff32668

Filter in the carb inlet fitting is clean? I have seen those carbs with the wrong needle and seat that prevents proper float drop settings.

Edited by Shepherd on 08-09-21 01:15 PM. Reason for edit: No reason given.

Posts: 466

Reg: 07-09-18
09-01-21 04:26 AM - Post#2826368    
    In response to jeff32668

Make sure that the needle is properly mounted on the float tab. I've seen people assemble a Quadrajet improperly. The little wire hook needs to attach to the end of the float tab. Otherwise, it will not open and thus, no fuel.

I think that is what is happening.


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