Vacuum gauge
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Joined: Mar 2018
Posts: 66
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From: Davenport Iowa
Vacuum gauge
I installed a inside the car vacuum gauge in my 77. Can I tee off the vacuum line going to the headlight pull down switch, or should I pull vacuum directly from the manifold? I was thinking..vacuum is vacuum, but there I go thinking again! I know there are valves etc in the system, so I would like to do it right the first time.
Thanks
Thanks
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
Those light switches can be finicky about vacuum and working properly. I would stay away from that and maybe find a manifold vac source elsewhere. If you have an automatic there is a vac line going to the tranny you could "T" off of. All the other ports are likely being used for priority systems like brakes, distributor and PCV.
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Joined: Mar 2018
Posts: 66
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From: Davenport Iowa
Ok..and I DO have a automatic...th400.
Last edited by John Swift; Jun 23, 2018 at 08:43 PM.
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Well thats the convenience of a vacuum gauge. You can monitor whatever system/process you want. But be careful of crankcase pressure as often the crankcase has positive pressure that could allow gasses to enter the passenger compartment - for those gauges you would want to mount them outside and more likely use a combination vac/press gauge. But that will show you the effectiveness of your PCV sys.
Normally for engine diagnosis you want to connect to the manifold vacuum. With this you can see the smallest of engine loads and can observe a bad/burnt valve in real time.
But you can connect on the downstream side of the little check valve to monitor accessory vacuum (head lights).
Hope this helps.
Normally for engine diagnosis you want to connect to the manifold vacuum. With this you can see the smallest of engine loads and can observe a bad/burnt valve in real time.
But you can connect on the downstream side of the little check valve to monitor accessory vacuum (head lights).
Hope this helps.
Thread Starter
Advanced
Joined: Mar 2018
Posts: 66
Likes: 1
From: Davenport Iowa
Well thats the convenience of a vacuum gauge. You can monitor whatever system/process you want. But be careful of crankcase pressure as often the crankcase has positive pressure that could allow gasses to enter the passenger compartment - for those gauges you would want to mount them outside and more likely use a combination vac/press gauge. But that will show you the effectiveness of your PCV sys.
Normally for engine diagnosis you want to connect to the manifold vacuum. With this you can see the smallest of engine loads and can observe a bad/burnt valve in real time.
But you can connect on the downstream side of the little check valve to monitor accessory vacuum (head lights).
Hope this helps.
Normally for engine diagnosis you want to connect to the manifold vacuum. With this you can see the smallest of engine loads and can observe a bad/burnt valve in real time.
But you can connect on the downstream side of the little check valve to monitor accessory vacuum (head lights).
Hope this helps.
Thank you guys!!
Last edited by John Swift; Jun 24, 2018 at 09:24 PM.
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Thread Starter
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Joined: Mar 2018
Posts: 66
Likes: 1
From: Davenport Iowa
Yes Bob and Derick, I have found it to be extremely useful for a few different things. That's why I decided to install a full sweep one inside.
When I first got this beast I was getting 9 mpg, It needed a lot of tuning. Last I checked it was 17 and now waiting for the weather to improve to see what I am now getting.
As someone told me, "mileage.. who cares, it's a vette", and I agree to an extent, but why throw money out the window for nothing! With every MPG I get a little bit better performance as well! Thx
When I first got this beast I was getting 9 mpg, It needed a lot of tuning. Last I checked it was 17 and now waiting for the weather to improve to see what I am now getting.
As someone told me, "mileage.. who cares, it's a vette", and I agree to an extent, but why throw money out the window for nothing! With every MPG I get a little bit better performance as well! Thx