First post but longtime reader.
I have a 72 W30 that I am restoring and am having vacuum issues. The motor is all rebuilt and ran fine until I drove it about 30 mins with the dist. not torqued down enough and I suspect it retarded the timing excessively. It got hot enough to discolor my exhaust and has run poorly since. I suspected that I might have burnt a valve so I replaced the heads but it didn't seem to help. It seems to have an bad vacuum leak but I replaced all vacuum lines and even capped all vacuum ports in an effort to isolate the leak. I have changed the intake and carb gaskets numerous time an even replaced the intake with a brand new one. Compression test and leak-down test seem to be fine. Does anybody have any advise on what I could try next?

 

How did you arrive at this conclusion? Describe your troubleshooting process and someone might be able to spot something that you may have missed.

 

Ditto to Fun71. A compression and leakdown test would have told you whether you had any burned valves before you took the heads off, and once they were off, you would have seen for sure.
Did you replace them without even looking at them? And what did you replace them with?

- Eric

 

What are the symptoms of your poor running engine? What is your vacuum?

 

Since I discovered the distrib. had retarded it idles erratically and has a skip that I can't get rid of. Vacuum fluctuates at idle between 20-25 but if I hold my hand over the carb it jumps to 40 and the idle seems to smooth out.. I have tried searching for a leak with wd40 and brake cleaner but found nothing. Replaced plugs, wires rebuilt Carb. When driving the car it seems to run fine when accelerating but when you run it at a steady speed it has a skip that you can hear through the tailpipes