4.8 intake manifold vacuum port question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72LSLB · 02-27-2017, 08:34 PM

My 72 has a 2007 4.8 engine. There is a port on the passenger side of the intake manifold that is open and is sucking in air. When I plug it the engine rpms go down and the engine runs fine. This must have been for some sort of vacuum sensor or whatever. It's shown in the middle of this pic. Can someone clue me in to what it's for?? Thanks

jessemthompson · 02-27-2017, 10:31 PM

I had the same vacuum port leaking on my 5.3 when I first swapped it. Idk what it originally was for, but I plugged it and it runs fine.

72LSLB · 02-27-2017, 10:35 PM

Quote:

Originally Posted by jessemthompson

I had the same vacuum port leaking on my 5.3 when I first swapped it. Idk what it originally was for, but I plugged it and it runs fine.

Yeah I plugged mine and it actually made it idle at a lower rpm which is fine. Just wondered what it was actually for....

homemade87 · 02-28-2017, 09:05 AM

Quote:

Originally Posted by 72LSLB

Yeah I plugged mine and it actually made it idle at a lower rpm which is fine. Just wondered what it was actually for....

I have never seen it hooked up to any oem vehicle I have looked at . I am sure there was a least one application for it . Reason is is leaking is because the tip was snapped off during handling . They all had a piece on the end to snap off if needed . I used mine for the vacuum supply for the heater and air controls in my 82 .

72LSLB · 02-28-2017, 09:13 AM

Homemade87,

Excellent info! Thanks a ton!

ls1nova71 · 02-28-2017, 11:26 AM

Its for the HVAC system in vans, they still used vacuum controlled blend doors during the GENIII engine times.

homemade87 · 03-01-2017, 09:27 AM

Quote:

Originally Posted by ls1nova71

Its for the HVAC system in vans, they still used vacuum controlled blend doors during the GENIII engine times.

That explains why I had never seen on in use . I have never messed with a van engine .

solidaxel · 03-01-2017, 02:15 PM

Quote:

Originally Posted by ls1nova71

Its for the HVAC system in vans, they still used vacuum controlled blend doors during the GENIII engine times.

That is what I use on my 78 for the blend doors vacuum source

02-27-2017, 08:34 PM	#1
72LSLB Registered User Join Date: Feb 2017 Location: Harvard Illinois Posts: 76	4.8 intake manifold vacuum port question My 72 has a 2007 4.8 engine. There is a port on the passenger side of the intake manifold that is open and is sucking in air. When I plug it the engine rpms go down and the engine runs fine. This must have been for some sort of vacuum sensor or whatever. It's shown in the middle of this pic. Can someone clue me in to what it's for?? Thanks __________________ 1972 C10 Custom Deluxe 4.8 LS 4l60e

02-27-2017, 10:31 PM	#2
jessemthompson Registered User Join Date: Nov 2011 Location: Williamsburg, VA Posts: 960	Re: 4.8 intake manifold vacuum port question I had the same vacuum port leaking on my 5.3 when I first swapped it. Idk what it originally was for, but I plugged it and it runs fine.

02-28-2017, 09:13 AM	#5
72LSLB Registered User Join Date: Feb 2017 Location: Harvard Illinois Posts: 76	Re: 4.8 intake manifold vacuum port question Homemade87, Excellent info! Thanks a ton! __________________ 1972 C10 Custom Deluxe 4.8 LS 4l60e

02-28-2017, 11:26 AM	#6
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,119	Re: 4.8 intake manifold vacuum port question Its for the HVAC system in vans, they still used vacuum controlled blend doors during the GENIII engine times. __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html



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