Stock Vacuum at idle
 

Hey guys, I just installed a boost/vacuum guage. Right now the car idles at 10-12 mm/hg of vacuum. Im wondering if this is normal because my last car idled at about 20 mm/hg. I also have 272 cams, I think that might play a factor.

Before cams, i was at about 15ish. Now i'm right around 10.

So Im good then? Nothing to worry about?

no

I would say you're right on. I'm no expert, but i would say you have nothing to worry about.

I love not having anything to worry about! Thanks :thumbup:

Cams make a difference. After my Jun 272's and race port and polish headwork my vaccuum at idle is only ~ -4.5psi

I have gsc 272s and vacum is between -10 and -13

HKS 272's and am around 10-11 mm/hg of vacuum.

Not to flame on en1gama19 but how can your vacum be 1.4 PSI? Is that right or do you need a new gauge?

FYI:

This is HIGHLY dependent on your altitude. Stock, I saw -17in hg in chicago, -12 in hg in Albuquerque, and -7 in hg at 11000'.

EDIT:
Chicago - 600'
Albuquerque - 6500'

d

So which one is better high or low vaccum? :D Indication of vaccum leaks?

Generally a higher vacuum (more negative pressure reading) is better as it indicates a higher energy potential in the intake. In other words, the air is getting moved into the engine with greater force. With a longer duration cam, the potential goes down slightly, but the air has more time to enter and evacuate the engine -- thus higher flow.

d

Stock I pulled every bit of 20. Now w/ my 272/264 setup I pull between 15 and 18. I am down here in Auburn/Al, so I would assume I am not that far above sea level.

Generally speaking you want between 15in/hg and 20in/hg (.51bar-.68bar). Normally if your vacuum is lower than that, you may have cam timing issues. Don't forget that most fuel pressure regulators (including ours) need at least 15in/hg to operate properly at idle.

Darin

Not 1.4psi, - 4.5psi. Read it again ;)