Use of Vacum Gauge

[stevenelle]

Do some of you old hands consider the use of a vacum gauge to be a good diagnosis tool, and if so, what is a good reading at idle for these old engines? The gauge I have shows 17 - 22 to be "normal". Mine is right at 17 on the low side. The attached website indicates that you subtract 1 inch of vacum for every 1000 feet above sea level. At 1600 feet, that would put my truck below the normal range.

Other question relates to use of the gauge when driving instead of just idling. Are there other guidelines to use?

http://www.secondchancegarage.com/public/186.cfm

[greg g]

Normal is about 18 to 20 inches at idle for most engines. Have you tried adjusting your timing to see if andvancing it slightly will increase the vacuum.

On way of setting timing is to establish a good smooth idle, attach the gauge, and then rotate the distributor to achieve the highest reading.

So it may be that your timing is a bit retarded.

Here is a pretty good chart on what a gauge can tell you.

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

As far as driving with one hooked up, your job as the driver is to keep the vacuum as high as possible during opperation. Basically this means you drive by using as little gas pedal as possible. It can help you achieve good fuel economy, if you are even a tiny bit obsesive cumpulsive, the gauge may push you over the edge.