Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: Handyman57 on August 26, 2023, 04:22:54 PM

Title: Fuel pressure to High ?
Post by: Handyman57 on August 26, 2023, 04:22:54 PM

So been having trouble with fuel wicking thru gaskets, and carb seeming to load up . Found out I have about 8.5-9.0 psi.
Qjet is a 69' #7029223 that was rebuilt but I don't know much about it. It's on a 327 .030 over, just a mild cam with Edelbrock performer intake. Planning on tearing down carb this winter to check out and Rebuild with Cliffs kits but would like to drive  it a couple more months.

Title: Re: Fuel pressure to High ?
Post by: Cliff Ruggles on August 27, 2023, 12:17:40 AM

N/S not holding back the fuel.  Could be as simple as a bad part, incorrect install of the parts, leaking at the gasket under the fuel inlet seat (I see a lot of those), or fuel level just set way too high.....

Title: Re: Fuel pressure to High ?
Post by: Handyman57 on August 27, 2023, 05:19:55 AM

So the 8.5-9.0 psi is ok ?  Forgot to mention I have aftermarket auto parts store mechanical fuel pump. Hate using those but I had a new Carter and was junk out of the box.

Title: Re: Fuel pressure to High ?
Post by: Shiny on August 27, 2023, 07:45:43 AM

Having gone through a similar experience earlier this year, I concluded a healthy N/S should be able to hold 8 or 9 psi.  Following a method shared by Cliff, I actually measured mine and it held 12 psi before being overwhelmed.  Yours could be different (N/S dia, float, float fulcrum, etc.) but that's what I found.  Mine is a 69 Buick carb with a slightly larger-than-stock N/S dia and one of Cliff's nitrophyl floats.

There are lots of reports of aftermarket mechanical pumps supplying pressure over the "preferred" 5 or 6 psi but I wouldn't immediately assume 8 or 9 psi is a problem.

I recommend you start by rebuilding the carb with one of Cliff's kits.  While you're doing this, look for dirt.  I found rust particles inside my carb, ended up replacing the tank.  The source of my rust was the sending unit in the tank.  I also found rubber particles from a degraded hose.  These all got replaced with the tank.

Title: Re: Fuel pressure to High ?
Post by: Kenth on August 27, 2023, 09:30:37 AM

The fuel level in bowl will rise with increased fuel pressure.
Higher fuel pressure than std. (about 6 psi) will require lower setting(s) on the float to maintain the same fuel level.