That's about right... I read 19-21 when I had stock cams... When I put in 272/272's it went to about 13-15... WHen the A/C on, it goes to 10...

 

I must have 272's just like my tuner suspected. My vacuum does the exact same thing. That's good news for me.

 

19 or so with my Sterwart Warner boost gauge.

 

I get 15, works 269 cams and an altitude of 5500Ft

Mike

 

Stock cams, Autometer, 17 to 19 at idle, and 15 with a/c on. 15 psi in 1 through 3, and 19 in 4 and 5.

 

15 with cams 20 with none

 

mines like 14-15 with 272s

 

I had the Megan Manifold and the Megan o2 housing just installed and I also have the Cosworth Cams. I am using the Prosport Premium gauge and Mine reads around 10-12 is that normal? Before it used to read around 18-20

 

Prosport gauges stock cams, 19-20 at Idle. Yes I can confirm that it goes up to 16 or 15 with the AC on high.

 

Like most others, 19 at idle, 15 with the A/C on. Stewart Warner gauge.

 

I don't know if you are running a vac line through the firewall to the gauge but sometimes they get pinched at the firewall and will expand enough to read right at boost but not in vac. I would just double check that first.

Cams with play with vac at idle as well big time depending on how hairy they are.

Good luck,
~Tom

 

Mine is a digital gauge. So I am not sure whats going on. I re-ran all the vacuum lines and put brand new ones and still the same reading. And It happened after the o2 housing and manifold install.

 

stock i was at 19-20
now with hks 272's i'm at 14-15 at idel

 

its provably is the combination of everything. I am going to double check it on sunday when I got get the car Dynoed and tuned. They are going to gook up their data logging equipment so lets see if they match.

 

Interesting...but..vacuum doesn't fluxuate with altitude unless the idle speed is reduced......or mixture changed (;-), more likely the issue) I think that would be paramount to saying thinner air moves slower then thicker air...( dont think physics allows that) could be different vacuum in stock cars/cams as well...depending on cam timing, hence the need for cam gears...given the opportunity to tune a car paying attention to the vacuum alone...tune to the highest vacuum for a given idle speed... back in the day, thats the way you tuned for idle richness...by vacuum, going for the highest vacuum pulled by adjusting the mixture screws then idle..