Originally Posted by beltfed
The truck, after getting hot will buck and stumble through half petal but run good on full petal. Could this be the cap?

Try loosening or removing the cap and see if the symptoms persist. Another check involves disconnecting the vacuum advance to see if maybe a wire inside or near the distributor has broken strands that only show up at certain positions of the vacuum chamber. I've seen that one repeatedly.
Jerry

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