vacuum test

The vacuum didn't go to 0 because there was still some vacuum left,... make sense ? Same as when a 2 barrel carb would never see zero, but a 4 barrel carb would.
But why is Zero vacuum so important anyway ?

What are my options as far a unported vacuum sources?

64thunderbolt wrote:
where you put the hose had 2 sources of air. That is why it didn't go really low. Put it on a source that only has one hose hooked to the carb or throttle body. It will never go higher than you saw because the engine catches up as said before.

It only had two hoses.The other one didnt have any vacuum.I think that was the one that went to the egr.

where you put the hose had 2 sources of air. That is why it didn't go really low. Put it on a source that only has one hose hooked to the carb or throttle body. It will never go higher than you saw because the engine catches up as said before.

That would be a perfect vacuum. Drive 'er straight up 120 miles and you'll have approaching zero vacuum. As the engine operates camshaft timing and cylinder leakage would never allow anything close to 14.7 psi differential pressure. 1" hg mercury is very little "pressure".

Where would be a good alternative place to put the hose for the vacuum gauge on a 454 tbi engine?

I have it not right in the pcv but another line that runs off the pcv pipe and runs into the bottom of throttle body.It looks like it might run to the egr.I started the motor before i used it and checked to see if it was sucking and it was.

probably doesn't mean anything except that the port you're plugged into is ported vacuum (right in the venturi or very close) Or if the air filter is still installed it might be restricted.

Remember the pistons going down are trying to pull the air in through the carburetor and the butterfly in the carburetor is restricting the airflow causing a vacuum between those two points. When you floor the accelerator pedal the butterfly goes wide open and the air rushes into the manifold faster than the pistons can pull it out so the vacuum goes to zero until the engine catches up.