Duke Nukem
Sr. Member
Start with the basics. It has got to be fuel, spark or mechanical. Be methodical and systematically eliminate the possibilities.
The only thing that affects fuel would be possible debris in the tank, clogged fuel line, vapor lock (not likely in this case), carburator problems, or a bad fuel pump. You really should check your fuel pressure, which was suggested earlier. BTW, are you running a mechanical or electric pump? Some years back I used to have problems that I assumed was vapor lock but turned out to be a bad fuel pump. Ran great at idle but like crap on the road. FWIW, I ran an edelbrock for years and found that, other than being the worst offroading carb of all time, it actually was pretty reliable and ran well on the street. Every time I suspected the carb of being the problem it ALWAYS turned out to be something else. Nevertheless, it doesn't hurt to dissasemble the carb, clean everything out, and put it back together.
If it's spark then it is either the wiring, coil, distributor, plug wires, plugs, or timing. If it idles correctly I would probably assume that your plugs, wires and timing are good (for the most part). In the past I've had a bad coil that caused it to idle well but run like crap under load. You should also get a voltmeter and check your voltage to the coil and at the battery. Also pull individual plug wires to see if it affects your idle. Perhaps you're not getting spark to all cylinders. And for the sake of God, upgrade your distributor and get rid of those damn points!
Mechanical issues could be many things, but I would start by checking the compression on each cylinder. Heck, you should do that anyway just to know how healthy your engine is. Perhaps you have a bad valve and aren't getting good compression. Again, it might idle well but run lousy on the road.
Go step-by-step through the possibilities and let us know what you find.
The only thing that affects fuel would be possible debris in the tank, clogged fuel line, vapor lock (not likely in this case), carburator problems, or a bad fuel pump. You really should check your fuel pressure, which was suggested earlier. BTW, are you running a mechanical or electric pump? Some years back I used to have problems that I assumed was vapor lock but turned out to be a bad fuel pump. Ran great at idle but like crap on the road. FWIW, I ran an edelbrock for years and found that, other than being the worst offroading carb of all time, it actually was pretty reliable and ran well on the street. Every time I suspected the carb of being the problem it ALWAYS turned out to be something else. Nevertheless, it doesn't hurt to dissasemble the carb, clean everything out, and put it back together.
If it's spark then it is either the wiring, coil, distributor, plug wires, plugs, or timing. If it idles correctly I would probably assume that your plugs, wires and timing are good (for the most part). In the past I've had a bad coil that caused it to idle well but run like crap under load. You should also get a voltmeter and check your voltage to the coil and at the battery. Also pull individual plug wires to see if it affects your idle. Perhaps you're not getting spark to all cylinders. And for the sake of God, upgrade your distributor and get rid of those damn points!
Mechanical issues could be many things, but I would start by checking the compression on each cylinder. Heck, you should do that anyway just to know how healthy your engine is. Perhaps you have a bad valve and aren't getting good compression. Again, it might idle well but run lousy on the road.
Go step-by-step through the possibilities and let us know what you find.
