funny you say that as i bought a vac/pressure guage today...... are you saying when the engine is runnin it can show pressure not vacuum if the evac syatem isnt working also...

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Since you bought the gauge hook it up to the crank case
(I run my gauge on the back of the drivers side valve
cover), hook up the exhaust and run the engine at
assorted RPMs and take some reading on your vac gauge.
This is only reading the engine pressure. Then hook
up the evac and re-do the RPMs again and see if they
are higher or lower.If the valve in the evac were
to fail and you have more back pressure in the exhaust
it WILL back up into the engine pressurizing the
engine with hot exhaust gasses