Quadrajet problems

[nhramnl]

I'm tending to support the "float too high" or "too much fuel pressure" suggestion. If the carb was fine but isn't now, your problem doesn't sound like a weather change issue. It sounds like a float that's too high (or the functional equivalent or that, too much fuel pressure) causing fuel to splash out of the bowl vent, into the primary venturis. If you leaned and richened it and the stumble wasn't affected, that would confirm that you have "uncontrolled" fuel entering the intake manifold. The car goes momentarily rich, stumbles and then gets on its way.

[MR DERBY CITY]

Originally Posted by Hacksaw

Several builders use a sliding piece that the secondary metering rods fit through. If your carb has one of these, make sure you did not knock it out of position when you were changing rods. Take the top off and look.

To the best of my knowledge Danny Ashley was the first Q jet builder to use the sliding piece that the rods fit through. Most builders use tape or a piece of foam. That sliding piece can move when changing rods so this is an excellent observation Mr. Hacksaw...I sure miss Danny, what a wonderful man....

[ss3011]

Originally Posted by nhramnl

I'm tending to support the "float too high" or "too much fuel pressure" suggestion. If the carb was fine but isn't now, your problem doesn't sound like a weather change issue. It sounds like a float that's too high (or the functional equivalent or that, too much fuel pressure) causing fuel to splash out of the bowl vent, into the primary venturis. If you leaned and richened it and the stumble wasn't affected, that would confirm that you have "uncontrolled" fuel entering the intake manifold. The car goes momentarily rich, stumbles and then gets on its way.

Sometimes if the float is too high or too much fuel pressure , you can look down the primaries with the engine off , turn on the fuel pump and look to see if fuel is dribbling out the boosters . I had that problem , but could not fix it with a float level adjustment . I measured 7 psi fuel pressure . I did fix it by installing a new needle and seat . Edelbrock still sells the .145" needle and seat .

[nhramnl]

Interesting comment on the needle and seat, and definitely a possible contributor to the problem. I was having similar problems and called Dean Oliver, to discuss reasons why the car was so stinky, smoky rich. We confirmed the float setting and fuel pressure were right, and the next question he asked was "You're not using a .145 needle and seat, are you"? When I told him I was, his response was "Get it out of there; they flow so much fuel that they actually disrupt the fuel in the bowl". I went back to the next smaller needle and seat and the problem went away.

[Todd Hoven]

Originally Posted by MR DERBY CITY

To the best of my knowledge Danny Ashley was the first Q jet builder to use the sliding piece that the rods fit through. Most builders use tape or a piece of foam. That sliding piece can move when changing rods so this is an excellent observation Mr. Hacksaw...I sure miss Danny, what a wonderful man....

It was originally done by Pontiac in the early 70's But he was the the only guy I know of that was milling the top to accept the slider plate.

It sounds like a float level could be high and or the fuel is going past the secondary metering rods because of loose tape or something. I'd stay away from the .149 needle and seat in a qjet. They are pretty sensitive and prone to blowing over unless you run less then 5 1/2 pounds of fuel pressure. A .135 is a good choice, and you can make plenty of power with it.

Dean is also a great guy and a good choice for a carb

[HP HUNTER]

Originally Posted by Stk4996

This past weekend in Ennis we acquired a stumble off the starting line that we never had before..
goes on the two step to 4600 clean no stumble but when launching it caughs a few times being a tenth and a half slow to 60' and 4 tenths down track..
we fattened it up and stumble was worse so we leaned it out some more and was faster down track but still had stumble..

Need to talk to someone that understands these well and possibly that I could send the carb to, to have it looked at...
Trying to get something going quick to make Noble and Dallas National.. thanks in Advance

Matt Diamond

Whats your fuel system like?

[Stk4996]

thank you all for the info... got to Talk to Dean this morning and this evening, checked a few things ourselves and came up with nothing... so the carb is boxed up and on a ups truck heading to Dean...

Thank you all again for the help,
Matt Diamond

[Mark Yacavone]

This one's on the way, via Buster Brown, but we might want to mention there is a secondary accelerator pump circuit. This was discussed in an earlier thread.
My experience is that you just can't take a Qjet that is being booted off the line, and then use it with a 2 step. If your spring is tight and your vacuum break is of the slow variety, you may be pulling fuel out of the secondary circuit.
The biggest eye opener for me was to have the driver mat it while watching with the hood open. In my mind, if the secondary flap is not WFO when releasing the brake or button, then consistency and efficiency will suffer.

[4543]

Check the fuel pressure gauge against a known good one.

[Mike Pearson]

Originally Posted by MR DERBY CITY

To the best of my knowledge Danny Ashley was the first Q jet builder to use the sliding piece that the rods fit through. Most builders use tape or a piece of foam. That sliding piece can move when changing rods so this is an excellent observation Mr. Hacksaw...I sure miss Danny, what a wonderful man....

Danny did some beautiful work on Q jets.