318 Runs like crap

Sounds fun, It seems like it may a distributer issue, possible mechanical or vacuum advance issue.

Sound like an problem I had, I doubt it's the same unless the distributer was the original or at least a high mile one..

My 318 always ran great until I did some basic upgrades, headers, intake, carb, etc.

The point being, during this time the distributer was pulled out for more room to work and it had no visible excessive ware, so it was reused and put back in. All seemed good on start-up, fast idle a little ruff but expected, timing was dialed back (with the vacuum advance unhooked and capped) and carb adjusted to maintain idle and once up to temp the timing was checked and was in a working range about 7 degrees. So I began to advance the timing and adjust the curb idle screw to maintain idle and this was not a easy as I expected, extremely small distributer adjustment seem to have a larger effect then it should have. And as I got closer to where I wanted test runs began to show power loss or vibrations.

This all turned out to be a combination of a weak mechanical advance inside the distributer, and a slight bend in the distributer shaft (not noticeable by eye or finger feel). This was causing excessive timing under load and a slightly difficult setup, I have come to believe that the distributer could have been like that for a long time, but never had a chance to show itself because it was locked into position until I took it out for the work. And after a new distributer, all was good again.

I'm not sure if this will help but I have come to find, only test and replace one part at a time when diagnosing a specific problem, if you change 2 or more you may never know for sure which part was bad and which one was just looking old.

good luck, let us know what the outcome is