I know this has been posted before but I can't seem to find it using the search feature...for everyone running an aftermarket Vacuum/boost gauge, what vacuum are you guys seeing at idle (I seem to recall that it should be 20-21 inches). My new Lunar gauge shows about 17-17.5 inches at idle and will go to 20-21 inches under hard deceleration...any ideas? I've also looked in my online manuals to see what factory spec vacuum is but I haven't been able to find any values.

Thanks in advance,

Dan

P.S. I've already checked the boot and the t-fitting and all is good there and the gauge is zeroed when the truck is off.

 

mine reads 20#

I don't know what altitude will do for vacuum, how much are you above sea level?

 

Don,

About 2500 ft. and it's a balmy 95-100 degrees here. Didn't even think of the altitude or temperature affecting it...come to think of it most of the guys I recall posting were hiding around sea level or so. And boost with a chip, 4 lb. lower, 1.5-2 lb. upper and a K&N and airbox mod is only 12 lbs. or so at full tilt...you might be on to something here! Knew weather would affect my boost just didn't dawn on me that it might do the same for vacuum.

Thanks,

Dan

 

Mine hovers around 18-20

 

Yeah Hamma...I saw the pic of yours at about 20-ish but again, you're one of those low level (speaking strictly from an altitude standpoint) MA guys...

Dan

 

HI!... Mine reads 26 at idle.

 

Neal...damn you man! I feel woefully inadequate with my paltry 17 inches!

 

I was checking the same thing. My Autometer Phantom was reading around 17 at idle. I checked it on a real vacuum gauge and it was at 21. Hope this helps.
Graeme

 

lol