Vacuum Gauge

[profaqualung]

I pulled my vacuum gauge out a few years ago when I went to a 383 engine - filled the hole with a oil temp gauge.

This past week I put the vacuum gauge back in its original hole and hooked it back up.

But the readings while running down the road, do not seem to be what they were before I took it out - as near as I can remember.

My questions -

What should the gauge read at idle with a carburetor engine?

What should it read at around 70?

What would the reading be under "passing cars" type acceleration - not pedal to the metal?

Currently, all the gauge readings are way to the right hand side. I know I have a little carburetor issue which will be addressed tomorrow, but am just curious as to what the vacuum gauge should be reading once the carb is retuned.

Thank you

[Gunslinger]

At idle, you should see 17"-21" of vacuum and hold steady. That can change with a different camshaft profile. If you have a "bigger" cam, you'll see lower vacuum readings. If you have a cam that gives a lopey idle, you'll see a very uneven vacuum reading.

It's possible your gauge needs lubricating after sitting in storage. I've seen where some people recommend a drop of brake fluid or penetrating oil into the gauge's working parts to free it up. I don't know how good or bad that might be for the gauge but they say it works.

Vacuum gauges are one of the most useful tools in engine tuning...at least for non-computerized engines. There's lots of information online about vacuum gauges and using them and how to read them.

[profaqualung]

Thank you Gunslinger. We adjusted the carb and the gauge is still reading further to the right than I remember. Will try the lubricating trick you suggested and see what happens.