Valve on exhaust manifold???
Thread Starter
Junior Member
Joined: Jan 2000
Posts: 46
Likes: 0
From: Indianapolis,IN
Valve on exhaust manifold???
This isn't on my bird but my 86 chevy truck. On the passenger side there is a valve on the outlet of the exhaust manifold operated by vacuum. I believe it is related to the EGR system. My question is, does the actuator pull the valve closed with high vacuum or does high vacuum open it? I'm thinking that at WOT you would want it open, not restricting the flow plus you wouldn't have the vacuum to pull it open therefore it should be open at low vacuum.
What I'm getting at is if there isn't a vacuum line to operate the valve it should be open all the time.
Am I right?
I hope someone can help me out here,
Thanks,,, Matt
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Dirt Late Model racer and Third gen lover.
91 V-6 bird with 406 in process.
What I'm getting at is if there isn't a vacuum line to operate the valve it should be open all the time.
Am I right?
I hope someone can help me out here,
Thanks,,, Matt
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Dirt Late Model racer and Third gen lover.
91 V-6 bird with 406 in process.
Supreme Member
Joined: Jul 1999
Posts: 1,294
Likes: 1
From: was: Palmdale, Ca
Car: was: 1984 Camaro Z28
Engine: was: L69
Transmission: was: 700-R4
Ahh, the infamous EFE (Early Fuel Evaporation) valve. 
What this does is it "helps" the engine warm up faster by restricting the exhaust flow. It is actuated by a ported vacuum switch when vacuum is high when cold. When the vehicle gets warmed up, the ported switch removes/de-activates the vacuum going to it. It only works when the vehicle is cold. You can get rid of it, unless you live in really cold weather where it could be beneficial (I don't see how 
). IIRC
Edit: had to fix smileys.
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George P. Lara
Z28s Owned:
1984 "L69" A4
1994 LT1 M6
Member: SCCA, SCFB, SC3GFB
Camaro Info: MadMike's
[This message has been edited by MRZ28HO (edited December 26, 2000).]
What this does is it "helps" the engine warm up faster by restricting the exhaust flow. It is actuated by a ported vacuum switch when vacuum is high when cold. When the vehicle gets warmed up, the ported switch removes/de-activates the vacuum going to it. It only works when the vehicle is cold. You can get rid of it, unless you live in really cold weather where it could be beneficial (I don't see how ). IIRC Edit: had to fix smileys.
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George P. Lara
Z28s Owned:
1984 "L69" A4
1994 LT1 M6
Member: SCCA, SCFB, SC3GFB
Camaro Info: MadMike's
[This message has been edited by MRZ28HO (edited December 26, 2000).]
Supreme Member
Joined: Jul 1999
Posts: 18,457
Likes: 16
From: Loveland, OH, US
Car: 4
Engine: 6
Transmission: 5
It is normally open, and vaccum pulls it closed. There is a temp vacuum switch that only sends it vaccum when the coolant is below some arbitrarily cold temp. Its purpose is to help the car run better quicker after a cold start. When closed it forces the right bank exhaust to go through the head, through the intake under the carb, though the other head, and out the left side of the Y-pipe. It has nothing directly to do with EGR.
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"So many Mustangs, so little time..."
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"So many Mustangs, so little time..."
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