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#1 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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how to correctly use a vacuum guage..
I bought a vacuum guage awhile back.....im not really sure how to use it. (I understand you plug it into the vacumn line,but which one) Ive heard you can tune your motor to get better mileage with it..
Can somebody tell me if I should keep it or return it or let it set in the box. Shine some light on this subject please.
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#2 |
member #16
![]() Join Date: Dec 1999
Location: Yuba City Ca.
Posts: 3,618
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Re: how to correctly use a vacuum guage..
Heres a diagram chart.
http://www.classictruckshop.com/club...ts/vac/uum.htm
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john http://67-72chevytrucks.com/vboard/showgroups.php board vendors ![]() http://www.flickr.com/photos/1745471...7602865984234/ |
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#3 |
Big Red - Now its a SWB!
Join Date: Jun 2009
Location: Oroville, Ca
Posts: 1,624
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Re: how to correctly use a vacuum guage..
you can use these to help tune the carb, mainly the idle mixture (and on holleys you use it to find what power valve to use). The specifics of how to use it depend on the carb you are running......so what you got?
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68 3/4 ton ![]() ![]() 41 3/4 ton ![]() 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's |
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#4 | |
Big Red - Now its a SWB!
Join Date: Jun 2009
Location: Oroville, Ca
Posts: 1,624
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Re: how to correctly use a vacuum guage..
Quote:
I forgot that you can use them as a diagnostic tool, I thought he was more interested in carb tuning since he mentioned milage. Oh yeah, you connect it to a vac port that has full vacuum (one that is on the intake manifold or one that is on the base plate of the carb)
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68 3/4 ton ![]() ![]() 41 3/4 ton ![]() 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's |
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#5 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: how to correctly use a vacuum guage..
edelbrock 500cfm electric choke (not hooked up though) its running nearly pefect.
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#6 |
Big Red - Now its a SWB!
Join Date: Jun 2009
Location: Oroville, Ca
Posts: 1,624
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Re: how to correctly use a vacuum guage..
sorry I'm more familiar with holleys, but I know that if you go to the edelbrock website you can find tuning guides in the tech section. Good luck!
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68 3/4 ton ![]() ![]() 41 3/4 ton ![]() 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's |
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#7 |
Registered User
Join Date: Jan 2006
Location: Take Off
Posts: 1,908
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Re: how to correctly use a vacuum guage..
I once hooked one up to my carb and taped it to my windshield so I could find out what power valve to use. Not too smart, would not do that again.
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#8 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: how to correctly use a vacuum guage..
ok
Is it worth bothering with? And which vacumn port do I plug it into?
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#9 |
Registered User
Join Date: Jan 2006
Location: Take Off
Posts: 1,908
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Re: how to correctly use a vacuum guage..
Yes, it's worth it but you have to study the vacuum gauge directions and possibly consult a carb tuning guide to really understand how to use it. You would hook it up to full manifold vacuum, (i.e., below the carb throttle plates). It is a device for the person who really wants to spend some time tuning his engine and has the patience to really study it, IMO.
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#10 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: how to correctly use a vacuum guage..
so its really not worth a 17 year olds time lol...id like to understand it but am not very good at carb. tuning lol
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#11 |
Registered User
Join Date: Jan 2006
Location: Take Off
Posts: 1,908
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Re: how to correctly use a vacuum guage..
I consider it a somewhat esoteric tool for the carb tuning nerds that really want to make a study of it, like me. I like that kind of stuff but many backyard mechanics don't have the patience or the time to really understand how engine vacuum can be a window into how your engine is performing.
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#12 |
Active Member
![]() Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: how to correctly use a vacuum guage..
If you have several vacuum ports look to see if you have below the butterfly valve- that's manifold vacuum and it's the one to use. Ported vacuum is above the butterfly valve.
Keep the gauge. I bought one many years ago and it sat in a box for several years. Then I started having problems with the carb and had to put a kit in it. Needless to say, the gauge came in handy again. I've used it several time since to refine the carb for maximum vacuum at idle. Theoretically you can isolate different problems from bad valves to ignition problems with these gauges. I've ownly used it for carb adjustments. |
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#13 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: how to correctly use a vacuum guage..
ok well if i go hook it up
ive got a hose going from dizzy to carb.(which would that be) ive 1 port high on the left, and 1 low on the right (i THINK the dizzy goes to the lower one on the right)which one do i hook it to?
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#14 |
Registered User
Join Date: Jan 2006
Location: Take Off
Posts: 1,908
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Re: how to correctly use a vacuum guage..
Lower is full manifold vacuum. However, if the vacuum advance canister was hooked up to it, you may need to use a T so you can keep vacuum going to the vacuum advance canister while you tune the carb up with the vacuum guage installed.
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#15 |
sharp as a marble
![]() Join Date: Jan 2007
Location: atlantic beach,florida
Posts: 1,082
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Re: how to correctly use a vacuum guage..
vacuum gauges can be a wonderful diagnostic tool if you let it.
you can use it to adjust timing, by watching the gauge and turning the distributor until you have your highest vacuum reading. Sometimes you will have a gas ping, and will need to back off the timing a bit use it to know what power valve you need diagnose a burned valve make sure you have enough vacuum play with it, understand it, the gauge is a powerful tool |
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#16 |
Registered User
Join Date: Jan 2006
Location: Take Off
Posts: 1,908
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Re: how to correctly use a vacuum guage..
"Luke, my son . . . may the vacuum force be with you."
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#17 |
Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: how to correctly use a vacuum guage..
Ok i'll try to play with the vacumn guage this weekend (gotta fix my wheeler first, so i can sell it to buy more stuff for the truck
![]() so i want the most vacum reading on the guage as I can...without pinging GOTCHA any more replys??...
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John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4 |
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#18 |
Registered User
Join Date: Mar 2003
Location: Cheboygan, MI
Posts: 998
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Re: how to correctly use a vacuum guage..
When you're driving, they are also a good idicator of potential gas mileage. If you're running a lot of vacuum, your mileage will suck...
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Tony Johnson -- '71 Blazer w/L-31 Vortec 350, SM465, NP205, performer intake, edelbrock 1406, HEI, 4" lift, Boyd EFI tank, Vintage A/C My Blazer -- |
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#19 |
BlahBlahBlah
Join Date: Feb 2002
Location: Wa.
Posts: 19,881
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Re: how to correctly use a vacuum guage..
Here's one I have, I got it off the 72 C10 Burb I gave to my son.
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#20 |
Senior Member
![]() Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,285
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Re: how to correctly use a vacuum guage..
This subject came up last year in a thread titled: _Vacuum Cluster_ by Its70 on 4/03/2008. Sorry I don't know how to link threads.
Anyway I use a vacuum gauge [Mooneyes 2-1/8"] in the dash of my daily driver. It tells me a lot about my engine's internal condition while moving. I have another hand-held Vac gauge in my tune up kit and we use it for tweaking up the carb. It's a great instrument, once you get the hang of it.
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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