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I have less than 800 miles since rebuilding my m38's engine this spring. I was driving it last week and it was running great. Then I had to slow down for a car in front of me. Hit the case and it started coughing and hesitating. Got back up to speed and it was running fine, slow down and the problems start again. I took the carb apart and found no issues, put it back on still having problems. I do need to change the head gasket, the one I put into the jeep was not good and started leaking after just a few miles. Would a bad head gasket cause the problems?

If the engine behaves well cruising and when you try to accelerate it stumbles then the two normal causes are either the accelerator pump in the carb or the centrifugal advance in the distributor. Occasionally a leaking spark plug lead will only cause the miss under acceleration loads. Suspecting a head gasket is really pulling for straws on this one.

The head gasket is leaking as well. I am not thinking it is the only problem. I do have a protronix kit in the dist and everything was free and looked good this spring when I had it apart.

Even with the Pertronix everything below that plate is the stock centrifugal advance. Can only be checked by pulling the cap and rotating the rotor by hand.

For the carb accelerator pump just remove the diaphragm cover and inspect the diaphragm.

Also it goes without saying that all ignition system wiring integrity has been checked and fuel level in the bowl has been checked.

I checked the bowl float level and it looked good. I also did check the diaphragm and other than being discolored looked good and was still flex-able.

To add to things the jeep is running really rich. However after taking the carb apart and cleaning it, plugs in #1 and #4 seem to be getting better, however the plugs in #2 and #3 are still very sooty and black.

I was right, the head gasket is gone. It went bad between cyl #2 and #3 between the exhaust valves. Looks like someone hit the gasket with a plasma cutter.