loosing boost

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Apr 1, 2011 | 04:13 PM

jbrenner0188

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From: pa

loosing boost

i have a p1 with a 3.5 pulley and am only making 5lbs. of boost where is it going.i am pretty shure the belt ant slipping.if someone can help please post.

Apr 2, 2011 | 02:56 PM

MadIceV8

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What size crank pulley are you using?

Apr 2, 2011 | 03:07 PM

HydroStream6

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Also what CI, heads exhaust, everything about the car.

You can't just post "I have a problem what is it?".

Apr 5, 2011 | 04:48 PM

jbrenner0188

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From: pa

stock crank pulley.all stock motor.with longtubes and and y pipe and bullet with dump. has fuel pump and 48 lbs. inj.2800 stall with 4l65 stock rear.

Apr 6, 2011 | 06:38 AM

Bob@BruteSpeed

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Quote:

Originally Posted by jbrenner0188

stock crank pulley.all stock motor.with longtubes and and y pipe and bullet with dump. has fuel pump and 48 lbs. inj.2800 stall with 4l65 stock rear.

Assuming you have a six rib ProCharger kit, the crank pulley would be a small 6.0 size. Unless you live up in high elevation, I would expect it to make a little more boost than 5 psi.
How dirty is the air filter? A clean air filter will allow the blower to make more boost, sometimes several more psi.
To check for belt slippage, look at the blower housing to see if you have black dust on it. The blower belt has to be much tighter than the other belts to prevent it from slipping.
A bypass valve that is not closing far enough can also be the problem with low boost. In the closed position there should be a slight airgap, but nothing as large as an 1/8+.
You could also have a leak somewhere between the blower and the throttle body in the tubing. Make sure all the hose clamps are tight, and check for any possible leaks. Sometimes you have to cap the tubing at the throttle body and at the blower, with one of the caps having a schrader valve installed so that the tubing and intercoolers can be pressurized.
The boost gauge could also be faulty, check the boost with a second gauge to confirm that it is actually at 5 psi.

Hopefully this helps and you find the problem. Bob

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Apr 8, 2011 | 03:54 PM

jbrenner0188

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From: pa

what is the right way to adjust the bypass valve..i have it making 7 now.it is a 6 rib kit.

Apr 9, 2011 | 08:39 PM

MadIceV8

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Quote:

Originally Posted by jbrenner0188

what is the right way to adjust the bypass valve..i have it making 7 now.it is a 6 rib kit.

What did you fix/change to get you more boost? 7psi sounds about right for that pulley size setup.

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Apr 12, 2011 | 04:09 PM

jbrenner0188

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From: pa

fuel pump,it was loosing press. not it holds 60 + so at 6000 it is now making 7psi. i am looking for 10 at 6500..also i have stock cam now bob when i put ur blower cam in will it loose boost?? or stay the same

Apr 13, 2011 | 11:21 AM

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Bob@BruteSpeed

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Quote:

Originally Posted by jbrenner0188

Ouch!!! So it was running so lean that it wouldn't rev?

My blower cam will cause it to lose a little boost, which can then be compensated for with a smaller head unit pulley. Thanks. Bob

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