What should my boost gauge read?

SCobsessed

Registered User
everyone has probably heard this question before. But my damn hayes manual dosent tell me anything about what my boost gauge should read at idle, and at full boost on my stock 89.
right now the needle sits at the i under in hg at idle, so like 18 pounds vacume. And at full boost im not sure exactly. i am usually looking at the road under such situations...but i think it tops out around the the s or i in PSI...so like seven or eight pounds...i think it should be at seven correct?....time for me to do some reading i guess Just concerned i might have a minor boost leak.
 
seams a little low.
at idle, it should read around 20
full boost should read about 11-13
 
crap

crap i figured as much...i hace noticed the engine feels a little weak at times...and the back end dosent come out when i hammer on it in second around a corner anymore....so....damn....where should i look what should i reseal, what do i use to reseal the system, anyone know?
 
A few ideas

Not sure which model year yours is. I have a 94 5spd. I would look to make sure the bypass valve is working correctly. On my 94, the bypass valve is located at the back of the engine near the fire wall. It uses vaccum to operate. As you increase throttle, the bypass should CLOSE so that all the SC air is forced into the engine. I had some problems with the Ford vaccum line (really small); it kept slipping off. If you look at it closely, the OEM hose has large rubber "fittings" on each end and has a small diameter plastic hose in between them. I replaced it with the correct size rubber vaccum hose (can't remember what size it is) and clamps and have had NO problems since.

Also, the vaccum line from the engine to the boost gauge on mine was made out of that same small plastic hose. It got a bit clogged and my boost gauge started doing funny things. I replaced that with regular vaccum hose as well and NO problems.

If you're sure the car isn't performing, I'd check the bypass valve first. You can do this by letting the car idle, opening the hood and reving it up under the hood while watching the valve. If not, the poor gauge performance may have you convinced something is wrong when it's not (I've had things like that happen more often than I'd like to admit).

Good luck.
 
My 89 SC auto with stock exhaust would boost 12 lb.

With MAC CAI, 76mm C&L, 10% pulley, 95 Mustang headers, 2.5" high flow cats, and dual 2.5 to single 3" res to 3" out no mufflers the car boosted 13 lbs.

I added a 75mm TB and now I am getting 14-14.5 lbs boost.

Jerry
 
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