I know there’s 1000 threads on vacuum and I think I’ve read them all, but here’s my question. I’ve got a 79 pig with a Weber 38. I recently replaced the coil/dizzy with the Redline cruisers kit. Timing is set to 9 degrees and idle is 700rpm. I only have 3” of vacuum off the carb port, which increases to 20” with throttle. I have 20” of vacuum at an intake port which is capped. All the readings are steady. If I run a vacuum line to the dizzy advance from the intake port, I see no difference in driving performance than I do coming off the carb port. I’ve hosed the base of the carb and the spacer plates with carb cleaner and got no change in idle, so I don’t think there’s a leak there. Why do I have almost no vacuum through the Weber? Can that port be plugged and it needs to be cleaned out?
Yet another vacuum question
- Thread starter MHFJ
- Start date
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With the butterfly closed you should be generating the most vacuum. As you step on the gas the butterfly opens letting in more air and fuel which reduces vacuum.
Can of carb spray is cheap enough to spray out hoses and ports. Maybe your vacuum advance is stuck by being shellac from old oil, hose it down.
Can of carb spray is cheap enough to spray out hoses and ports. Maybe your vacuum advance is stuck by being shellac from old oil, hose it down.
- Thread starter
- #3
Doh! Why didn’t I realize that? So 2-3” of vacuum off the carb port is normal at idle?
- Thread starter
- #4
The dizzy is all new non-U.S.A. Toyota.
middlecalf
SILVER Star
Dang, I accidentally deleted my post 
. Yes, ported vacuum comes on with throttle.
. Yes, ported vacuum comes on with throttle.
Just because it is new doesn't mean its good. Likely not gummed up, but there could be a burr, cracked diaphragm, over torqued fitting - doesn't take long to inspect it so you know its good vs assuming IMHO
pb4ugo
SILVER Star
Your carb is aftermarket and can be installed on various engines. The ported vacuum may be by design. Some applications may require ported vacuum instead of manifold vacuum for some fixture.
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