what is this and its function? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tim21391 · 03-11-2013, 12:24 AM

what is this part and what exactly does it do... dont laugh but to me it looks like an egr valve but i doubt a 72 402bb has one being that old haha...its diaphragm operated off vacuum off the carb.. it runs smooth with it unhooked and sucking vacuum with it uncapped.. hook it back up you can see it function til its sucked shut and then it sounds like the motor is "cammed" i assume since its there it needs to be hooked up.. truck runs fine just curious to what it is

thanks
tim

LODI3QTR · 03-11-2013, 12:53 AM

It's the vacuum diaphragm to open the vent on an AC cab..........

SS Tim · 03-11-2013, 01:49 AM

That is for the air recirculation door. The air inlet is from the right kick vent. If you don't have the factory manuals then download them here, as there is a wealth of information.
http://67-72chevytrucks.com/vboard/s...d.php?t=558016

daves72C10D · 03-11-2013, 05:49 AM

Not to hijack the thread, mine is sheared off at the firewall. I have not looked at a manual, how hard is it to fix?

Andy4639 · 03-11-2013, 06:27 AM

I did away with mine and sealed it up. The AC works fine as does the heat.

SS Tim · 03-11-2013, 07:51 AM

Quote:

Originally Posted by daves72C10D

Not to hijack the thread, mine is sheared off at the firewall. I have not looked at a manual, how hard is it to fix?

You have to pull the cowl panel to access it. See page 1A-35 of the 72 service manual linked above.

Quote:

Originally Posted by Andy4639

I did away with mine and sealed it up. The AC works fine as does the heat.

Andy, It is not a redundant part or function. If you sealed the valve opening up all you are doing is recirculating cab air all the time.

tim21391 · 03-11-2013, 09:51 PM

ok sounds good thanks guys

03-11-2013, 12:24 AM	#1
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	what is this and its function? what is this part and what exactly does it do... dont laugh but to me it looks like an egr valve but i doubt a 72 402bb has one being that old haha...its diaphragm operated off vacuum off the carb.. it runs smooth with it unhooked and sucking vacuum with it uncapped.. hook it back up you can see it function til its sucked shut and then it sounds like the motor is "cammed" i assume since its there it needs to be hooked up.. truck runs fine just curious to what it is thanks tim __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796

03-11-2013, 12:53 AM	#2
LODI3QTR Registered User Join Date: Apr 2012 Location: Smithtown New York Posts: 156	Re: what is this and its function? It's the vacuum diaphragm to open the vent on an AC cab.......... __________________ LEFT LANE IS FOR PASSING!!!! SLOWER TRAFFIC KEEP RIGHT!!!! My C20 & Cars... http://67-72chevytrucks.com/gallery/...&ppuser=111212

03-11-2013, 01:49 AM	#3
SS Tim Registered User Join Date: Aug 2010 Location: Edwards, CA Posts: 7,507	Re: what is this and its function? That is for the air recirculation door. The air inlet is from the right kick vent. If you don't have the factory manuals then download them here, as there is a wealth of information. http://67-72chevytrucks.com/vboard/s...d.php?t=558016 Attached Images __________________ Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID Blazer SPID Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders Do you have a 1972 Plaid Pickup? Plaid Blazer ** Plaid Suburban

03-11-2013, 05:49 AM	#4
daves72C10D Registered User Join Date: Mar 2004 Location: Vale, NC Posts: 283	Re: what is this and its function? Not to hijack the thread, mine is sheared off at the firewall. I have not looked at a manual, how hard is it to fix? __________________ 1972 Custom 10 Deluxe- original paint, interior- 72k miles http://www.cardomain.com/ride/2466316 Cheap, Fast or Good. Pick any two. 1990 Eagle Talon AWD 1991.5 W250 CTD 1992 Cushman Truckster- Haulster

03-11-2013, 06:27 AM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: what is this and its function? I did away with mine and sealed it up. The AC works fine as does the heat. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

03-11-2013, 09:51 PM	#7
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	Re: what is this and its function? ok sounds good thanks guys __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796



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