Question concerning Vac\Boost

crabmustang302

Registered User
I have about 15 in vacuum at idle and only making about 8 psi boost upto 4000rpm then goes up to about 10 psi till it shifts at just over 5000 rpm, is this normal?

Car seems to be running rich under WOT, black smoke out tailpipe,
What I have done to corrects this is clean MAF and ACT sensors.

Car seems to have less power since exhaust.

What I have is a 90 SC with AOD, stock 3.27:1 gears, stock manifolds, custom 2 1/4" y-pipe with no cats, and factory exhaust from there back, air silencer pulled, high flow panel air filter.

Any ideas?

Thanks
Garett
 
on my 89 and 90 vac is closer to 20 in park or neutral maybe 15 in drive .on my 89 standard with good exhaust has about 10 pounds of boost at 3500 the 90 has about 15 pounds of boost at 3500 with stock exhaust i hardly ever go more rpm. if it feels slow and even revs slow in neutral i would be checking harmonic balancer
 
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It revs cleanly with no load in park, I looked at the balancer today and its running straight and bolt is tight and not broken.

I think it feels slower due to the lost boost after exhaust, I lost about 5-7 psi boost after I had the y-pipe done (I had resonator removed also at same time)

Just wondering if I should put a 5% or 10% pulley on and will get my power back?

Also what does everyone else have for vacuum at idle 15 in seems low to me for a stock motor? (maybe I have a vacuum leak but it idles pretty smooth)

Just trying to get some ideas, any input will be appreciated

Thanks
Garett
 
my balancer had no wobbles there was no way of tellin till i took it off , it kept getting slower after about 3 days it would barely go up hill better exhaust you should definatley notice improvement in my opinion
 
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