Quote:
Originally Posted by HO455
Try putting your timing light on each plug wire and running the the engine up to the rpm with misfire and see if the light flashes indicate a misfire. Does the flashing show smooth movement as the timing advances and retards on each cylinder?. This should help you decide if the problem is fuel or ignition. My first thought was that you have a bad ground inside the distributor at low RMP (advance) and once the advance mechanism moves the plate enough the ground is restored and the engine runs as it should. Have you tried disconnecting the vacuum line to the vacuum advance and running it?
I would concentrate on the ignition side before diving into the carburetion side. It would be easier to swap the distributor with a simple point style to prove the ignition is good or bad than swapping carbs. The fact that the problem gets better with RPM leads me to believe that you don't have a cap or plug wire problem.
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HO455, thank you for the suggestions. I'll give the timing light process you mentioned a shot. One thing to note, as I mentioned I am running Live Wires which are an 8mm wire with 2mm heat resistant cover. I noticed when setting the timing, the light would get odd RPM readings, sometimes half of what it should be or zero, when on #1. If I jiggle the induction pick-up it comes back where it should be but it "lost" the RPM several times each time I used this light.
Regarding the distributor, I started with a stock Delco HEI which had an Accel High Energy coil, switched that out for a new DUI cap, rotor and high energy coil, swapped that out for the entire new DUI drop in unit with same specs but an upgraded Dyna Module. The problem never changed with these upgrades and was present before I started "hunting". I doubt the distributor could be the issue since the various combinations produced the same issue, but its possible. I also ran a set of 8mm Taylor wires prior to the Live Wires with the same results.
I have run the truck with the advance disconnected under load but not since the carb / distributor were changed. I did this prior to the new carb and prior to the distributor upgrade but it was the same before and after.
Thanks again for your replies.