I would go with Ted's suggestions. What often happens to inline engine like the slant is that hard summer driving puts alot of heat into the iron exhaust & intake manifolds. If you shut it down right afterwards that heat will boil the gas in the carb- causing a super rich condition on hot start. If local summer gas blends were changed to something with higher vapor pressure, that would make things worse. The fix would involve doing things to keep the carb cooler: airflow from a fan, heat shields, etc.

This is seldom a problem on modern EFI engine because the fuel rail is under pressure- even after shutdown,. Also the combo int/exh manifold design is very rare, so most injectors & rails don't see the same temps as a slant (or jeep 4.0L) do.

If you think you have a spark problem, then use an adjustable gap spark tester & see if you system can produce a 3/8 to 1/2" spark at the plug wire end while cranking during a hot soak.

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63 Valiant Wagon
225 - 4 bbl