What should vacuum be at idle

I have adjusted the screw on the YH to achieve the highest vacuum and smoothest idle. I am seeing air fuel ratio of around Checked for vacuum leaks and found none.

It starts and runs very well now. Just curious if what I am seeing is out of the ordinary. Heads are fresh with new springs and valve job. Last Updated: 17th July, Idle vacuum for most engines is about 18 to 22 in. If vacuum is steady at idle but lower than normal, the ignition or valve timing may be retarded. Low compression, an intake leak or tight valves also can cause low vacuum at idle.

Leide Negrini Professional. Does power valve affect idle? Conclusion: An open Power Valve has no effect at all on idle. The fuel from the PV is not being discharged at idle , since it must discharge from the main discharge nozzles. Melibea Greben Professional. What causes poor engine vacuum? A vacuum reading at idle that is much lower than normal might indicate leakage through the intake manifold gaskets, manifold to carburetor gaskets, vacuum brake booster or the vacuum modulator.

Low readings could also be caused by very late valve timing or worn piston rings. Noel Heckendorf Professional. How do you check engine vacuum? The simplest to perform is the running vacuum test. To begin, start the engine and let it run until it has reached normal operating temperature. Find a vacuum port to connect the gauge to. Ideally, it should be on the manifold or below the base of the carburetor.

Tohami Natalia Explainer. What happens when intake manifold pressure is low? Lack of power. Edward Yagodin Explainer. Share More sharing options Followers 2. Recommended Posts. Kwyjibo Posted January 23, Posted January 23, edited. Does anyone know what it should be sitting at with no accelerator input? Any easy ways of finding vacuum leaks? Cheers, Adrian Edited January 23, by Kwyjibo. Link to comment Share on other sites More sharing options Posted January 23, Kwyjibo Posted January 24, Posted January 24, RPR33 Posted January 24, Posted January 24, edited.

Sweet it was just my gauge!!!!! Idle Vacuum is is a measure of how well the engine can idle. If the engine has good idle stability, it will produce lots of intake manifold vacuum, which means it requires very little air and fuel to idle. An engine with a race cam which has high overlap period of time with both the intake and exhaust valves are open will idle rough. Then you must open the throttle to speed up the idle RPM to keep the engine running.