With two carbs, you might not see any vacuum difference when adjusting, just set them where they idle best and forget the gauge for now. How does it idle, smooth? rough? quiet? lots of air noise? rock solid?
Your next problem, during a test drive it dies? This sounds like dirt in the fuel tank blocking the pickup tube. Try mounting a fuel gauge, temperary, where you can see it when driving. I bet you find it loosing pressure, after it sets a bit, the dirt falls off the pickup tube and it runs again. Under driving conditions, the fuel requirement is much greater then setting in the garage idling.
Here are few more things to check.....
Is your fuel cap vented, try a test drive with the cap a little loose
have you done a search around the intake flange using a hose, with the other end in your ear, checking for any leaks?
Fresh fuel? old gas runs like crap,
Timing, would have to be way off not run,
low compression, would run, just have no power,
coils, would run till they get hot, takes a while for them to cool back off,
How are the valve adjustments, do you hear any poping out of the carb or exhaust? is the vacuum gauge steady or is it bouncing?
Joe
