I am glad that I ran across this thread. I have been having the same problem with my '51 Chevy 3100. Will start right up when cold, but will not start after having run awhile.
Started it yesterday to back it out of the garage so I could do some work inside. A couple hours later started it up again to drive it the 100 yards to my house driveway to give it a bath.
After the wash started it and took it for a drive of approximately 30 minutes, then parked it. After sitting for about 30 minutes, tried to start it to put it back in the garage, but it would not start no matter what I did with the choke. Lifted the hood and saw that it was dripping gasoline from the fuel line where I have it connected to an inline filter.
This has happened to me several times before. I am new to stove bolts and do not have much experience with them. I did not know that this problem existed with the Rochester carb.
At least now I have an idea of what the problem may be.
Thanks.

A question: I have been using a plastic in-line filter about six inches in front of the carb. Was the glass bowl filter original to the 1951 216 engine? Are there any advantages/disadvantages to this type of filter?