Posted by gary on March 03, 2000 at 17:12:51:
In Reply to: WM300 Timeing / skipping under load. Any help appreciated. posted by Bob on March 03, 2000 at 16:12:20:
I doubt that timing would cause "skipping". I guess it depends on
exactly what you mean. If you mean that the truck lurches and/or coughs
under load then it is probably a fuel starvation problem. This could be caused by
a plugged filter or a flake of dirt floating in the float bowl of the carb.
If it is a steady miss in one cylinder so that it runs of 5 under load then you have a plug
misfiring. This could be due to a bad plug wire, a cracked or dirty distributor cap or
a fouled plug.
I don't know what else. Any other ideas guys?
Your timing may indeed be off but the symptoms would be different. If it is too advanced, you
will get pinging. If it is too retarded, the engine will seem very weak in all ranges but shouldn't
"skip".
I have set the timing on many low-tech engines by warming up and turning the distributor back and
forth at idle and listinging. First turn in the direction the rotor turns (this is retarding the spark). The engine
will slow down and die if you go too far. Then turn back and it will speed up. There will be a noticeable point where
it seems to smooth out and additional turning will not speed the engine up so much. Beyond this point, the engine will
speed up more but will not run so smoothly. It is a trial-and-error process but seems to be ok for my '52 Chevy farm truck.
A slightly more accurate technique is to hook up a vacuum gauge and set the distributor for the point just after the
retarded range where you get maximum vacuum. Of course, a light and proper specs is best.