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Hello,
I rebuilt my Quadra Jet (68 Toro). It appears to run well, except that I have a momentary bog when I accelerate hard. I checked accelerator pump discharge and noticed that I get two streams, but only on the first 25% of throttle travel, then nothing. Any suggestions on what I may have messed up?
Thanks.
Other potential causes are incorrect float level, low fuel pressure, incorrect adjustment of the secondary air valve wrap spring, or leaking vacuum break diaphragm on the secondary air valves.
I reused the old ball, since it looked OK. I replaced the whole stem assembly. I didn't notice any dimensional differences, but I will have a closer look.
Thanks.
A couple things besides what Joe and the others recommended. Are you able to get a timing light on it to see if the distributor is advancing ok? Also do you have mixture screw adjustment? If so the throttle plates should look like this with the carb upside down. If the transfer slot is too far exposed (as pictured) work the mixture screws and timing to get the correct throttle blade position.
My buddy had me look at his carb for an accelerator pump issue. Found the rubber plunger dislodged from the stem. We put a new one on and shortly after he had the same issue. He opened the carb and found the same thing. He bought a new rubber pump plunger that was slightly bigger, no issues. I did not know there were different sized plungers for the quadrajet?
My buddy had me look at his carb for an accelerator pump issue. Found the rubber plunger dislodged from the stem. We put a new one on and shortly after he had the same issue. He opened the carb and found the same thing. He bought a new rubber pump plunger that was slightly bigger, no issues. I did not know there were different sized plungers for the quadrajet?
The problem is the material the plungers are made from are not compatible with today’s fuel. I had the same issue with my Q-Jet. I had lousy accelerator pump shot, when I took the top off I found the plunger separated from the pushrod. I put in a plunger from old rebuild kit I had sitting around. Six months later, same thing. I got a replacement accelerator pump assembly from Cliffs Q-Jet, no issues after that.
We old school knuckle dragging gear heads are a tiny minority of cars on the road. Obviously the refineries are going to formulate gas to work with the majority of consumers. Today’s cars are designed to work with ethanol fuels.
The same issue exists with manufacturers of carburetor rebuild kits. I’m guessing there just isn’t much of a incentive to update the materials used in the overhaul kits you buy from AutoZone or Advance Auto. If you want quality parts, your going to have to source them from someone who has invested in providing quality.
We old school knuckle dragging gear heads are a tiny minority of cars on the road. Obviously the refineries are going to formulate gas to work with the majority of consumers.
Well, actually, refineries are required to formulate cat urine, er, I mean gasoline, that complies with federal laws about ethanol content, as a concession to big agribusiness. New cars are designed to make due with that. The feds don't give a rip about how that effects owners of older cars, lawnmowers, chainsaws, etc, etc.
I recall reading somewhere that some 2 barrel Rochester carbs had bigger accelerator pump bores. You can machine the Q-Jet body to use the bigger accelerator pump plungers. I question why that would be needed. The Q-Jet accelerator pump works pretty well if it’s in good condition.
Pretty sure the accelerator pump information is in Cliff Ruggles Q-Jet book. He also states that most of the time poor accelerator pump shot issues can be traced to the check ball not sealing well against the body. He outlines a process using a old check ball to create a new sealing surface for the new check ball to seal against.
I adjusted the accelerator pump arm and got a much longer shot. My bog reduced substantially.
Looks like the stem was close to fully compressed in the rest position, so that it was close to the "overtravel" spring loaded range, which explains why I got a brief squirt at the start of the stroke. I will keep playing with it.
I did not know there were different sized plungers for the quadrajet?
I don't know if there are different sizes for the QJet, but I do know that there are different sizes out there. When I bought the Holley reman carb that's on my car, the accelerator pump would not move in the bore because the pump cup was too large. I called the Holley tech line and they asked what color the plastic part the cup attaches to was (I don't recall what it was now), they said it was the wrong one, and sent me the correct one (different color) and it fit perfectly.
I've had the same issue with a Rochester 4 jet, accelerator pump, cup would split and be found at the bottom of the bowl. Did this for about 4 rebuilds, much irritation was had. Sorta fixed it by using a NOS antique leather cup I'm still running with the leather with no issues. And 4 jets do have two different size pistons, may or may not be the same for a QJ.... Tedd
Great just got my carb back from rebuilder and it has a dead spot too.
im getting 1/4 squirt then nothing, mine has not fallen off tho. maybe i should try the ball bearing trick?
August 25th, 2020, 05:10 PM
