Home » Public Forums » GMCnet » Vacuum gauge (Where to measure vacuum?)
| Vacuum gauge [message #99519] |
Mon, 13 September 2010 00:25  |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
Karma: 0
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I finally have gotten to the point of finishing small projects, and would like to finally hook up the vacuum gauge I had purchased and installed in my lower dash panel. Where should I install the T to get the most useful reading? I assume that the line that goes from the manifold to the two way valve (at the front of the manifold) would give a good reading, but I would like to know what others have done. If there is better access point that would give helpful readings, I would use that one instead.
Thanks for any advice!
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] Vacuum gauge [message #99545 is a reply to message #99539] |
Mon, 13 September 2010 08:29  |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Bruce, you said you have "electronic spark control"......can you share the
details on that ??
Thanks
Ray
Ray & Lisa Erspamer
78 Royale Center Kitchen
TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMC-Royale@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/
________________________________
From: Bruce Hislop <bruce@perthcomm.com>
To: gmclist@temp.gmcnet.org
Sent: Mon, September 13, 2010 8:04:14 AM
Subject: Re: [GMCnet] Vacuum gauge
I connected mine as close to the manifold as possible. There was a dual
connection on mine, one output ran to the heater controls and the other was part
of the vacuum advance through the temperature vacuum switch.
Since I have electronic spark control, this is no longer used so I picked up the
vacuum there.
Also, since the cruise control was not working, I cheated and used the hose
going up to the brake pedal vacuum switch to connect to the gauge.
Here is a good page on interpreting vacuum readings.
http://www.bdub.net/vacuum.htm
--
Bruce Hislop,
S. Ontario Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: Vacuum gauge [message #189768 is a reply to message #99524] |
Fri, 09 November 2012 20:10 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Senior Member |
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| g.winger wrote on Mon, 13 September 2010 05:51 |
Vacume gages can be very usefull for diagnosing as well. Like it can help show why you have a miss at idle, or maybe a bad rocker arm. it will even help show that you have a bent valve right before a big trip you might have planned. Don't ask me how I know,,,,,
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Paul,
Your Cad 500 had a bent valve?? Have you figured out yet how that happened? What cylinder? I bent one also on #7. The intake. The only witness marks were when I pulled the head I found all kinds of brass colored pock marks on head of the piston, but nothing on the head or valve.
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Vacuum gauge [message #189789 is a reply to message #99519] |
Sat, 10 November 2012 08:13 |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
Karma: 0
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Senior Member |
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Larry,,,,yes. Right before the Int. rally in Ill. Was pulling out of the garage and it had a slight miss. Thought that was odd???? hooked up vac. gage and it was low and the needle was moving alot???? Had made a copy of the vac. gages off a web site(Barracuda) but could't find it. Went online,,,HOLY COW,,,bent valve!!! Can't be. No way. Compression test,,,can't remember but it was arond 50-75. Pulled the left rocker cover and a rocker arm had failed.(Larry,,,,remember what you said about mods,,,KAOS) This was a high quality Probe set up from Potter. Probe replaced the rocker and purchased a new SS valve(2.18 dia.) from Potter. Time was tight and the Boss was unable to lay on the floor and turn the crank even with my largest breaker bar. So adjusting the valves was tough.( Adjusted in the shop the first time,,,full front pull). Also,,,you get any snow yet,,,,,,PL
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| Re: Vacuum gauge [message #189790 is a reply to message #99519] |
Sat, 10 November 2012 08:15 |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
Karma: 0
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The pin on the roller nose had walked out and cocked sideways. I,ve got full roller ,pivot and valve tips,,,,,,,PL
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| Re: Vacuum gauge [message #189828 is a reply to message #189790] |
Sat, 10 November 2012 18:18 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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| g.winger wrote on Sat, 10 November 2012 08:15 |
The pin on the roller nose had walked out and cocked sideways. I,ve got full roller ,pivot and valve tips,,,,,,,PL
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And Paul, why weren't yall in Amana with us? that is as close as it gets. We missed you.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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