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06-20-2003, 02:19 PM
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#1 |
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Formerly yellow72custom
Join Date: May 2001
Location: Austin, TX
Posts: 7,531
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Vaccum reading?
I was playing around with my new vaccum guage, and i found 19" of vaccum at idle from my truck. It bounced up and down quickly between 18.5" and 19.5". Is this a normal, healthy reading? My engine specs are in my signature....
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'72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg |
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06-20-2003, 02:22 PM
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#2 |
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Registered User
Join Date: Oct 2002
Location: Des Moines WA. (Kent, area)
Posts: 668
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I believe thats really good, mine are only like 16-17
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70 chev c10 swb fleet 72 grill, sb 400, 2/4 drop. 68 chev c10 swb fleet Early classic 4/6 drop with 4wheel disc brakes 9"rear 67-8 buckets tilt and A/C Classic GM Truck Club of Washington . |
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06-20-2003, 02:58 PM
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#3 |
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Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,051
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Where does your needle sit when the truck is not running ?
I saw one and it sat at 10.
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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06-20-2003, 02:59 PM
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#4 |
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Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,051
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GMC pauls page has some good info on how to read the vaccume gauge.
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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06-20-2003, 03:03 PM
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#5 |
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Formerly yellow72custom
Join Date: May 2001
Location: Austin, TX
Posts: 7,531
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Good info. My needle sits at 0, so i guess my motor is in good shape.
Thanks for the help.
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'72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg |
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06-20-2003, 04:07 PM
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#6 |
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Glowing since 1978
Join Date: Mar 2001
Location: Lusby,MD,USA
Posts: 532
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Your reading should be steady. The fluctuation between 18.5 and 19.5 indicates something is not acting right. I'll have to dig out one of my reference books to let you know what they think could cause this. I know that a low steady vacuum is typically caused by cam profile. You often see this on a fresh rebuild with a hi lift/long duration cam. Here is the link to GMC Pauls info.
http://www.gmcpauls.com/Tech%20Tips1.htm
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66 Chevy C30 Stakebody Dump, PS,PB, 327cu in 71 Corvette Coupe 454 4 speed 69 Chevy C20 Custom Camper |
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06-20-2003, 06:11 PM
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#7 |
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Account Suspended
Join Date: Sep 2000
Posts: 3,991
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Mine sits about about 20 at 600 rpm
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06-20-2003, 09:45 PM
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#8 |
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Formerly yellow72custom
Join Date: May 2001
Location: Austin, TX
Posts: 7,531
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The truck runs great, so i doubt there is anything seriously wrong with it. In one of my books, it said a steady fluctuation like that can be caused by ignition problems. My timing is on just right, but i noticed my HEI had a bit of slop in the shaft when i pulled it out not too long ago.....
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'72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg |
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