Compression Testing

N

Norm M

Member
I am looking for a reference on the proper way to test a Model A engine for compression and what the results should be with a standard, 5.5 to 1 and 6.0 to 1 head. Any help would be appreciated.
 
Engine at operating temperature.
Remove all spark plugs.
Block throttle wide open.
Connect compression gauge for one cylinder.
Spin engine over 5 or 6 or more times, you will hear it grunt on each compression stroke.
Write the reading down.
Repeat for each cylinder.
 
30 Closed Cab PU said:
Add a squirt or 2 of oil to each cylinder? Think I saw this mentioned somewhere but am unsure if it is the correct way to do it.
Click to expand...

The correct way? The short answer is "Yes and no"!:confused:
The first compression test should be done dry. To check for worn rings, a little oil down the bore, then repeat the test will tell you. The second reading would be higher.
 
I recall reading that compression with stock head= 60#, 5.5 head= 75-80# Do not remember the source.
BUT, also see from my file folder scribbling some different numbers???
Standard-60#
Police-70-75#
5.5, 6.1 90-100#
PLEASE, anyone have the correct numbers? Chap
 
wet dry testing..compression low,squirt oil,if it goes up rings are bad,if it stays the same valves are bad..leak down test more accurate.
 
So now you know how to perform the test [ as Katy said].
Try it dry and then wet and see what you get. Let us know.
Rather than expect certain readings, difference between cylinders is the important part. Some of these old monsters will show low readings but run just fine. A compression test does not give any indication of condition of the oil rings.
 
Don't forget cold hot. While you can open the throttle, it really does not make much difference open or closed on a Model A engine.
 
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