What should my vacum be reading at say 80mph cruising? Mine reads -10, i thought it should be closer to 0 at a speed liike that? the truck idles at -20.

Nate

 

It should be about that. The more load, the lower the vacuum. So at a steady cruise it should be somewhat high. It should only read zero at close to full throttle or at full throttle.

 

That sounds about right...stock cam I'm assuming also. I see about 17-18 in/hg at idle in gear, around 20 in park or neutral, and usually 0 everywhere else in between depending on the load and how much throttle that I have tipped in, I'll see any where from 7-8 to 12-13 while cruising. I have to take a long steady ride down the highway and observe the guage.