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04-13-2022, 02:31 PM
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#1 |
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Senior Member
 
Join Date: Nov 2008
Location: Cleveland, OH
Posts: 588
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Exhaust flapper
Hey guys, I have a question. I just purchased an 85 K2500 GMC with the factory 350 and noticed it has the exhaust flapper/close off to aid in warm up on the passenger side still attached.
There looks like a vacuum diaphragm that pulls the flapper however I have no hose going to it. Or is some sort of spring that loosens up when heated sort of like a choke on a carb? Which way allows the exhaust to freely flow? Pulled in or resting?
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1972 Cheyenne Super 20 Custom Camper 12 Valve Cummins/5spd manual 1972 Cheyenne Super Short Bed 557 Med Olive DK olive 1970 K5 Blazer Dark Gold 1966 Coronet 440 35k mile survivor 1991 Suburban 2500 454/4L80E 2wd 1985 Monte Carlo SS 383 Sbc, t-56 magnum 6spd and Ford 9" Last edited by j_cst_10; 04-13-2022 at 02:38 PM. |
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04-13-2022, 05:35 PM
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#2 |
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Registered User
Join Date: Jun 2014
Location: CO
Posts: 737
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Re: Exhaust flapper
When vacuum is applied flapper is closed, the vacuum hose usually runs from a thermal vacuum switch. No vacuum and the flapper is open so it is fine without a vacuum hose hooked up to it.
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79 Chevy 2wd BIG10 350 TH400 |
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04-14-2022, 08:30 AM
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#3 |
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Senior Member
Join Date: Nov 2008
Location: Cleveland, OH
Posts: 588
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Re: Exhaust flapper
Thanks for the reply. I figured it wouldn't make a whole lot of sense for it to close at zero vacuum such as a wide open throttle scenario, but wanted to make sure I wasn't missing anything.
__________________
1972 Cheyenne Super 20 Custom Camper 12 Valve Cummins/5spd manual 1972 Cheyenne Super Short Bed 557 Med Olive DK olive 1970 K5 Blazer Dark Gold 1966 Coronet 440 35k mile survivor 1991 Suburban 2500 454/4L80E 2wd 1985 Monte Carlo SS 383 Sbc, t-56 magnum 6spd and Ford 9" |
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04-15-2022, 07:18 PM
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#4 |
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Registered User
Join Date: Nov 2018
Location: Cali
Posts: 294
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Re: Exhaust flapper
Don't know if this will help, this is the diagram off my 83 305 showing the EFE valve vacuum line.
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