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#1 |
Registered User
![]() Join Date: Dec 2012
Location: Los Banos CA
Posts: 2,705
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HVAC Vacuum Reservoir???
I searched and could not find an anwser, so thought I would ask the question.
Do you have to use the stock Vacuum reservoir for the HVAC? and if so can it be mounted under the dash? Thanks Scott FYI 1970 C10 CST with factory AC LC9/6L80E
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1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: HVAC Vacuum Reservoir???
You don't have to use the factory vacuum reservoir and you can mount it under the dash. You will want to use a good canister that is made for vacuum and is at least as large as the truck unit.
Jim
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#3 |
Registered User
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Location: Los Banos CA
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Re: HVAC Vacuum Reservoir???
So you have to use a canister???
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1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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#4 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: HVAC Vacuum Reservoir???
I did not mean to throw you with the terminology! Plastic or metal can be used as long as the part is made for vacuum.
Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#5 |
Registered User
![]() Join Date: Dec 2012
Location: Los Banos CA
Posts: 2,705
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Re: HVAC Vacuum Reservoir???
Jim so you HAVE to use a canister? As in a canister is needed and will not work and will NOT work without it?
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1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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#6 |
Registered User
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
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Re: HVAC Vacuum Reservoir???
Hi firstc10, I went to auto schooling in the 70's and remember the vac tank well. It's purpose is to check and hold vacuum, because when you step on the gas manifold vacuum drops off, and the vacuum that was in the lines would be bled off into the intake and there would be no vacuum available. 2 lines hook up to the tank, engine supply, and the other line goes to the controls inside the cab. It can be hooked up wrong (backwards), so here is the test. Use 2 vacuum hoses, install them on the tank, put your finger over the open end of one line from the tank, then suck on the other line that is hooked to the tank. When you release the vacuum that you put on the hose, there should still be vacuum present on the hose that your finger is on. Another words you are acting like the engine would with vacuum present, then bled off, but there should still be vacuum remaining on the other line. Good luck, Brian Fuller
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#7 |
Registered User
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
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Re: HVAC Vacuum Reservoir???
I believe classicparts.com has that tank very reasonably priced. It mounted on the engine side of the evaporator housing in the engine compartment. 2 screws were used to mount the vac tank ball.
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#8 |
Registered User
![]() Join Date: Dec 2012
Location: Los Banos CA
Posts: 2,705
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Re: HVAC Vacuum Reservoir???
Thank you for the explanation would I still have a vacuum problem with a stock 2011 LC9? I was wondering if I could just eliminate the reservoir all together. If I need to keep it where is the best place to get vacuum from? Maybe I need to ask in the lsx area.
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1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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#9 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: HVAC Vacuum Reservoir???
The reservoir is an important piece for your controls in the cab of a vehicle. It holds enough vacuum in reserve, to make up for those moments when your engine does not make good vacuum. This keeps the heating and air conditioning dampers from cycling to a different position, when the vacuum signal drops from the engine while climbing a hill or driving in heavy traffic. The newer vehicles have electronic controls on a lot of their dampers and controls and do not require as much vacuum as the older vehicles used to. If nothing else, put the reservoir under your floorboard to keep the volume of your vacuum available but the reservoir is out of site.
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#10 |
Registered User
![]() Join Date: Dec 2012
Location: Los Banos CA
Posts: 2,705
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Re: HVAC Vacuum Reservoir???
Perfect thank you.
__________________
1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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#11 |
Registered User
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
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Re: HVAC Vacuum Reservoir???
Hi firstc10, as far as an available vacuum port on an ls goes, i know my 2001 5.3 has a unused port on the intake. If nothing is available, dodge, plymouth, and chrysler, into almost 2000's had a spare port that was capped off right at the vacuum line at the brake booster. The thick vacuum line went from the engine to this round check valve assy, and that pushed into the booster. The capped off line was used for cruise control, hence this is your vacuum supply and check valve all in one. You could install this check valve in place of the gm check valve (if it fits) you would not need to get a vacuum tank and add it to the vehicle. I hope i'm not confusing you in the process, but if the check valve fits it would be a clean install with minimal sized parts only needing the vacuum line from inside the cab to plug into the check valve at the booster. If you care to venture into this, take your old check valve out and go to a junk yard with this post printed in hand and i think they would help you. Good luck, Brian Fuller
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#12 |
Registered User
![]() Join Date: Dec 2012
Location: Los Banos CA
Posts: 2,705
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Re: HVAC Vacuum Reservoir???
I used the 1/2" port on the back of the intake that was for the brake booster. I put a tee to the vacuum reservoir and to the brake booster. So far so good.
Thanks for all the input guys.
__________________
1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR *SOLD* GO ![]() |
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