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DSpringer

Stalling Problem

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I have been unable to solve a crazy problem: When I come to a stop the engine dies - every time - unless I approach the stop very slowly or pull the accelerator knob out to raise the RPM above idle. It doesn't happen going in reverse. Float adjusted per spec. I have swapped parts using my three carbs and done several rebuilds to try to solve the problem but to no avail. Anyone else experience this?

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To determine if it is being flooded by fuel spilling out of the bowl, lower the fuel level 1/16" in the carburetor bowl. This should not impact performance.

 

If that doesn't fix the problem, try backing off the vacuum brake adjustment a couple of turns.

 

If neither of these work, try dribbling some MMO down the carb to see if it will fix the problem.

 

I am assuming that your idle speed is 450 -500 rpms and that your vacuum reading is 18-20 inches of vacuum at idle.

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Try Tom's suggestions, but should they not pan out, try resetting the combination of idle mixture and idle positioner screws.

 

Check and record the number of turns out for each mixture screw (that way you can recreate your existing setting if I am wrong) ;)

 

(1) Warm the engine to normal operation temperature

(2) Rev up the engine to clear mixture out of the intake

(3) Shut off the engine

(4) Turn the idle MIXTURE SCREWS in (clockwise) until snug.

(5) Back out the mixture screws one full turn (360 degrees counter-clockwise)

(6) Turn the idle POSITIONER SCREW in 1/2 turn

(7) Start the engine. It should run above idle

(8) Slowly lower the idle RPM with the positioner screw until the desired RPM is acquired.

(9) Drive the car. Slam on the brakes to a stop, and see if the issue is gone.

 

Jon.

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More swapping parts and adjustments and I got some improvement. I don't have a tach so I don't know what RPM I have at idle, or what the vacuum is. I just lower the idle stop screw and adjust the needle valves until I get that nice smooth idle. The needle valves end up being about 3/4 open.


Another problem, I get a lot of surging when accelerating in first and second gear. I've tried swapping out three different power valves with different spring tensions with  little or no improvement.

 

Tom, the vacuum brake adjustment is the screw with lock nut on the side of the distributor? What does backing it off do to the spark advance? Wondering if that might be responsible for the surging. According to the late Rolf Burdette the distributor was refurbished by Jake Fleming about 12 years past.

 

With my restoration projects done I'm just trying to get her to purr and be more of a pleasure to drive.

 

 

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Talking to myself, here. Installing the power valve from my collection that has the weakest spring appears to have fixed the surging. Theory: The PCV valve I installed is increasing manifold pressure, causing the power valve to remain partially open. It is the low pressure in the intake manifold that pulls the valve closed against the spring tension.

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Backing off the vacuum brake adjustment allows the mechanical advance to kick in at a lower engine speed, if the brake and advance are working correctly. Backing off a couple of turns to see if it changed your problem is a diagnostic procedure to determine if the problem was caused by timing.

 

You should buy a vacuum gauge, so that you can see the effect that the PCV has on the idle vacuum. If it is affecting your idle vacuum, you probably need a different valve. Did you buy you setup from Jake Fletcher?

 

Good power valves have a number stamped on them to let you know the opening vacuum requirement. Best performance is usually obtained with a 5.0-5.5 power valve.

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Thanks, Tom. I might try the vacuum brake adjustment just for fun. As I said in my earlier post, I bought the distributor from Rolf Burdette, and he said it was gone over by Jake Flemming. I have a spare that I had Jake do also, but they're so much fun to change out that I think I'll save it for a time when I need some cheering up. I'm pretty happy with how she's running now, but it would be good to know what vacuum I'm pulling. None of my power valves are numbered. Any suggestions on vacuum gauges?

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Have you checked your spark plugs to determine if the engine is running rich? Power valve problems usually cause a rich condition.

 

The Lisle gauges are accurate enough for engine and fuel pump diagnosis. There are others in the $20-$30 that also are accurate enough. You can get one from Amazon or your local parts house.

 

The power valve rating stamping may be on the edge of the nut part of the valve or on the top steel part.

 

I buy my kits from Daytona Parts Co, but Charlie Schwendler ( 716/662-9159 ) has the same kit with a better needle valve. They both sell the power valve.

https://www.daytonaparts.com/

 

Jake does a good job of setting the dwell, timing and vacuum brake. If your distributor has more than 5,000 miles on it, the setting could have changed due to wear. I connect my dwell meter to the condenser mounting screw on the coil for the V-8 cars and check for correct dwell to determine if there is enough wear to change the timing. The V-8 dwell is 36 degrees and my memory is that the V-12 is 42 degrees with the dwell meter set on 6 cyl mode. I has been a long time, so my memory may not be correct.

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