I put a vacuum gauge on the vacuum line that goes to the petcock. it looks like it going from 0 to 30, complete range of the gauge. anyone ever see this or know what would cause this?? it's going crazy I can't even see it. I've been searching vac. reading and the only thing I could find was valve springs cause it has the biggest sweep.
I have vacuum gauges for syncing the carbs, and the needle bounces like crazy with just a hose going to the fitting. You need to put a small needle valve inline with the gauge. The level of vacuum changes rapidly as the engine is running, and you use the valve to choke down the line and smooth out the changes.