I've run into this several times. There have been several different causes. As Baldy said, in a couple of cases it was the coil. I figger that it had a broken wire in one of the windings and it would make contact when cold, but with some expansion due to heat, it would lose its connection and wouldn't provide spark.
Another time this sort of problem was cause by a fuel filter that expanded internally and strangled itself to where it wouldn't flow when hot. This was on a F**d (although I hate to admit to having bought one new once) and I've never seen it on a Chevy, but I spose it's still possible.
Percolation is another possibility (again, as Baldy suggested.) You could test this theory by having a can of starting fluid on hand and giving it a shot when attempting a hot start. I've seen this most often on motors with aluminum intake manifolds and no heat insulator under the carb (just as he said
) but ya never know...there may be a source of heat near your fuel line or fuel pump that causes the gas to percolate off.
Probably the best way to approach it is to determine if it's failing to fire because of a lack of spark or a lack of fuel. The starting fluid (ether) trick should help isolate that, as would pulling a plug wire, placing the hot end near a ground source and cranking it while observing it to see if there's a spark. Not the easiest thing, but not rocket science, either. Some creative use of some wire and a helper to crank it makes this easier.
Just some ideas and things to check. Let us know what ya find, k?
