Engine pistons serve as suction pumps. The quantity and quality of suction/vacuum created is affected by the condition of the rings, valves, ignition, and carburetion. Problems in each of the indicated areas effect vacuum guage readings in a specific manner.
Engine problems that can be detected with a vacuum gauge are:
1. Defective points
2. Ignition timing
3. Spark plugs
4. Weak coil
5. Leakage at the intake manifold
6. Cylinder head gasket leakage
7. Piston rings
8. Sticky valves
9. Valve leakage
10. Weak or broken valve springs
11. Carburetion adjustments/problems
12. Exhaust back pressure
The vacuum gauge post is sort of under construction. Hopefully after we get all the information, photos and comments we can assemble into an easily readable format.
Any one having comments or additional information. - Please add.
Vacuum gauges were commonly available at the auto parts store.
Stewart Warner makes/made the gauges under the brand name of Motor Minder. These gauges should be fairly inexpensive and work well. You will have to purchase a length of vacuum hose and a hose barb to adapt the gauge to the Cub. I have two from the 1960s. Iâ€™m thinking I paid about $5- each at the time.
There are two currently on Ebay for $15.50 each, but these gauges do not have the readings in inches of mercury.
SnapOn sells a vacuum/pressure gauge set for $199.95. Heavy duty mechanics set. Do not purchase this set for occasional use on your Cub. I also own this set. For the extra $170-s you get a metal case, a number of fittings and a booklet on how the interpret readings.
Last edited by Eugene
on Mon Sep 17, 2007 6:17 pm, edited 1 time in total.