Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: CJK440 on June 22, 2018, 06:40:20 AM

Title: Choke pull off opening too fast or air door spring too loose?
Post by: CJK440 on June 22, 2018, 06:40:20 AM

If I am getting an initial lean bog with a transition from cruise to WOT, how do I determine if its the air door spring being too loose or the choke pull off relaxing too fast? When I floor the pedal I get a bog, my AF meter goes lean briefly then power comes back nice until redline.

Am I correct in understanding that the pull off just prevents that initial "hit" of vacuum from prematurely opening the air doors? I drilled out my pulloff orifice to use a restriction in the vacuum line. The orifice I drilled in a plastic plug is .019 and it seems to take about 2 seconds to go to full extension.

It sure seems to me like the doors are flopping open causing the bog and when the vacuum above the throttle plates equalizes the doors go back in proper position and open nicely the rest of the ride.

I can try a smaller restriction but will need a microscope to drill it.  :o

Is there a strategy to dial in one setting by itself then the other?

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: 77cruiser on June 22, 2018, 07:04:22 AM

Tighten the air valve just a bit. What's it set at now?

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: CJK440 on June 22, 2018, 11:02:54 AM

Not sure of the current setpoint. I gave it a 1/4 tighter and reduced bog but with noticeable decrease in acceleration at the top of the revs.

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: Frank400 on June 22, 2018, 05:54:53 PM

I would increase the size of the POE.

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: Cliff Ruggles on June 23, 2018, 05:00:27 AM

.019" is a pretty big hole for a plastic pull-off, and most of those need slowed down, not sped up.....Cliff

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: CJK440 on June 26, 2018, 09:09:48 AM

Its a metal pull off that I drilled the orifice out. I then used a .019 drill to pop a hole in a piece of polypro paint brush handle and jammed it into the vacuum line.

I think the hole drilled too big because of the power drill and plastic melting. I then popped a clean .015 hole thru an ABS golf tee stem and tried that and the release time was dramatically slower.

No bog but it may open too slow now.

Title: Re: Choke pull off opening too fast or air door spring too loose?
Post by: Cliff Ruggles on June 28, 2018, 03:57:57 AM

I find drilling the restriction in pull-offs difficult and often near impossible.  I use a tapered reamer instead which provides infinite control vs drilling them with precision bits........Cliff