Compression Test Results

Well, I've been avoiding it for 9 years because I was afraid of what I might find, but I finally broke down and did a compression test this afternoon. The results were better than I expected. It runs good, but never quite had the "ummph" I thought it should have so I thought that it might have a weak cylinder or two, but they were pretty consistent. It has about 140,000 miles on it.

1st test
#1 - 124
#3 - 129
#5 - 126
#2 - 135
#4 - 129
#6 - 136

2nd test
#1 - 125
#3 - 129
#5 - 130
#2 - 134
#4 - 129
#6 - 139

By taking 75% of the highest reading as the FSM says, that leaves a reading of 102 for the 1st test and 104.25 for the 2nd test to be considered normal. Looks like the ol' 225 is in fair shape.

 

was this a wet or dry test Bob? If it's a dry test, put a few squirts of oil in the cylinders and turn her over again. The readings for wet to dry should not be any more than 10%. That will tell you if the rings are fine. You can also do a leak down, with a few basic gauges, this will tell you how the valves are doing. Abnormally high pressures can also be a sign of carbon build up.

 

It was a dry test. Thanks for the tips. Maybe I'll give it a shot with the oil for a wet test.

 

another thing you can do is if its a running motor, spray a fine mist of water into the engine while running. the cold/hot contrast will break off alot of carbon on the valves etc. and might pick your cyl pressure up a bit more/prevent leak down a bit. must be warm when you do it tho. might do it before you try the wet pressure test for a solid reading. run it, spray it, let it cool, squirt oil and test again. i would love to read the new numbers. keep us posted!?!?
=)

 

Well, I found out today that I didn't do the compression test right. I didn't remove all of the plugs, just one at a time. Here's the new numbers will all of the plugs removed...

#1 - 155
#3 - 154
#5 - 157
#2 - 159
#4 - 157
#6 - 165

How do these look? I ran out of daylight and so I didn't get a chance to do a wet test yet.

 

Those numbers look really good to me. As high as they are, I dought the wet test will be more than 10% higher.

JB