My 71 Bump

[clemsonjeep]

I hate issues that just pop up at random. This time I've got a new issue going on. The last problem with it not wanting to idle ended up being a bad condenser which I switched out and then it went bad again a few days later. Not sure what happened there but it's been running great for the past several months. Then last Friday it started "missing" under acceleration. It idles great, revs fine while in park or neutral, but when you put it in gear and try to get up to speed it has a miss...stutter...whatever you want to call it. If I stand on it and get into the secondaries it will let off a loud POP from under the hood. This usually only happens if I drop it into 2nd gear and mash the pedal. The secondaries open up and a few seconds later the pop occurs so I back out.

What I've done so far:

checked timing - 10* BTDC
checked points - replaced with new set and gapped to .017
checked wires inside distributor - all appear good and tight (distributor was replaced just prior to purchasing the truck earlier this year)
visually checked for spark at each plug
swapped to different used but known to work ignition coil - a visible difference in spark intensity
removed top of carb (edelbrock 600) - cleaned and checked float levels
removed vac line from brake booster - made no difference so I plugged i and the idle smoothed out a little more so it is still plugged
removed vac line from distributor - checked with vac pump and the diaphragm is not holding vacuum so it is currently plugged as well
verified that I am getting mechanical advance
verified good flow from fuel pump

I think that covers everything. I can drive the truck real calm and probably never know theres an issue, but as soon as I need to pass someone or get out in front of traffic the problem shows up. From what I understand a pop from under the hood would indicate a lean condition creating a backfire through the carb. I've checked all vac connections and they appear to be good. The auto trans shifts as it should so I assume the vac modulator is working as it should without leaks.

The only other question I have is why my distributor seems to be so far to one side compared to most pictures I've looked at for reference. The vac advance is just about bottomed out on the water pump it's so far over that way. Here's a pic...

[clemsonjeep]

Replaced condenser just to confirm that wasn't the issue and there was no difference. I put the vacuum gauge on it tonight and get a reading of 18...with a steady needle.

The thing that keeps nagging at me is that I have one of these spark indicators that you lay against the plug wires and it has a spark inside it if you have spark in that particular wire. When I touch the coil wire it is just about solid. When I move between the individual wires just a few inches from the distributor I will get a very distinct spark on most of the wires, but 1 or 2 of them...I believe cyl 8 is the one I see this on the most. I can pull the wire off of the distributor and have a very strong arc between the cap and wire then replace it and still not have an indication on the spark indicator tool.

I know this tool isn't the best test, but being that it works on all other wires except 1 or 2 makes me wonder whats going on.

[clemsonjeep]

[Busboy]

I'd use an ohmmeter to check the resistance of all spark plug wires. If those check out I would certainly pull the plugs and see if you have some contamination on the insulators. When accelerating hard any minor deficiency in the secondary ignition system will show up.

[clemsonjeep]

I'd use an ohmmeter to check the resistance of all spark plug wires. If those check out I would certainly pull the plugs and see if you have some contamination on the insulators. When accelerating hard any minor deficiency in the secondary ignition system will show up.

Thanks...Got those issues sorted out a while back. Those pics were my first post in over a year...haha

[Lone Ranger]

I love the color on this truck!

[Bullitt74]

Great wheel / cap combo - much better than that other style you had on there.

Cool truck to start with!