I have a '53 235 in my '48 3/4T, still with the 4:57 rear-end. I'm pretty sure the engine is a full-pressure one from a car with an automatic (engine # LAQ 83376). The engine runs smooth as a top for my usual 3-5 mile trips around town every day. But when I take it out of town 10-15 miles at 40 MPH and really warm it up to the core, the idle speed increases and it seems to miss. It's kind of a fast slappity, bangity. When it cools down it goes back to normal. I haven't checked the timing when it enters this mode, but does it seem like a distributor problem?

1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.