3800 What should Vacuum PSI be at Idle??

[Bliss Racing]

So before i did the how plug fiasco...i was at -9.5 psi now i am at -8.2 at idle...also, before i saw 10.4psi of boost, now it will only hit 7.4 ..... WTF?!? I couldn't find a vacuum leak, could this have to do with the plugs?? They are gapped at .055

also, when i left NAPA, i went to take off, and the car died, wouldn't start for about a minute......

can anyone help?!?!?!?

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[rjaz gtp]

This is an interesting question and I have been wondering what the "average" idle vaccuum is at also? I am normally @ -16 at idle and get about 12 psi and WOT

 

[zeez gtp]

have you thrown a code? you should be around -18 to -20 at idle

 

[Bliss Racing]

Originally posted by zeez gtp@Mar 23 2005, 07:19 PM
have you thrown a code?  you should be around -18 to -20 at idle

[snapback]76562[/snapback]​

No codes...i heard that -18 to -20 is what you see on a standard auto meter boost guage, but on a scan, the norm is -9 to -10.......on my aeroforcetech scan guage, i was seeing 9.5 ish...but now seeing 8.4ish......wtf

IAC Position is reading 30.....i heard if it's under 40, there is a leak somewhere...i can't find one though!!!

 

[iliveonnitro]

Is vaccuum == MAP pressure?

Does 18-19Hg sound about right for my GT?

 

[dole21]

I get about -15, after the cam


before the cam was around -18-20

 

[sr71_rgl]

I see around 12"hg at idle with ported cam/heads.

 

[LPSPEED2]

i saw -10 at idle, but if you just lightly feather touch the throttle it will drop to -20 and then climb up to your max boost. I was getting about 15-16PSI boost, and then my motor went bood from boost stacking. The psi went up to 15-16 but there was really no power after about 10-11psi. My car is fucked up tho, so ?????????????????

 

[Bliss Racing]

FOund the problem i believe......vacuum leak between supercharger and intake mani....i think i need a new gasket

 

[sr71_rgl]

Originally posted by Bliss Racing@Mar 24 2005, 11:02 PM
FOund the problem i believe......vacuum leak between supercharger and intake mani....i think i need a new gasket

[snapback]76856[/snapback]​

Pretty common on higher mileage L67s. You might want to consider changing the gasket on the lower intake manifold as long as your doing the SC gasket cuz it's probably original too.

 

[Bliss Racing]

Originally posted by sr71_rgl+Mar 25 2005, 02:22 PM-->

<!--QuoteBegin-Bliss Racing

@Mar 24 2005, 11:02 PM
FOund the problem i believe......vacuum leak between supercharger and intake mani....i think i need a new gasket

[snapback]76856[/snapback]​

Pretty common on higher mileage L67s. You might want to consider changing the gasket on the lower intake manifold as long as your doing the SC gasket cuz it's probably original too.

[snapback]76909[/snapback]​

[/b]

No, complete motor rebuild 3K miles ago....the SC gasket is new as well, not sure why it went out, probably wasn't centered or something, oh well.