Checking some things on the 3.7 today and was curious if anyone had any input.

Vacuum at idle is just about 17.5 inches. This is taken from the 3mm fuel pressure regulator gauge. I haven't checked TIS or the manual but I was wondering if anyone knew what vacuum ought to be on a stock motor.

Second item - waaay before all the upgrades started, if I removed the oil filler cap when the engine was idling it ran like crap. Now, with the rebuild, it runs just the same (again - at idle) cap on or cap off. If I put my hand over the filler hole, I don't feel any vacuum in the motor.

Sooo...anyone have any ideas why this is? I'm thinking the cam changes the intake vacuum somewhat. Martin and I compared a while ago and his was more like 18 or 19 inches of mercury. As the valve timing changes with the new cam, I can see how the intake manifold idle vacuum changes.

I'm curious why the engine doesn't mind having the filler cap removed. This I can't quite figure out. Anyone have any ideas?

Thx

Jeff