Compression Test

N

nq50

Member
Hi all,
I decided to check my compression. After running the engine for a few minutes these are the results, 58,51,54 and 56. Good?, Bad?, Indifferent?. What do you guys think?
 
Indifferent, next time the head comes off lap the valves. If you like spending money pull the engine and give it a complete rebuild. If mine I would drive it until it presented a problem
 
You didn't say much about the engine. Is it run regularly or has it sat for awhile ? Do you try the test both dry and wet ? Are those numbers the highest the gauge registered after about 7 or 8 revolutions ?
If the test was only done dry, then you try it again wet and see if it makes a difference.
But, I'd recommend just driving it. It'll probably run a good long time.
 
The engine has only been run about an hour in the past year. I started it and ran the engine for about 2 minutes, shut it down, removed the plugs and did the test dry. The readings were taken after about 5 revolutions. Elevation 860 ft., central Massachusetts.
 
nq50 said:
The engine has only been run about an hour in the past year. I started it and ran the engine for about 2 minutes, shut it down, removed the plugs and did the test dry. The readings were taken after about 5 revolutions. Elevation 860 ft., central Massachusetts.
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Drive it for awhile. Maybe add a qt of ATF at each fuel up [ add ATF first and then add fuel].
 
Like Patrick said, drive it around a bit more before doing the test. It not so much the value of the readings but the reading being within a pound or three of the others.
 
What oil are you running, try a 15-40 diesel motor oil (yes detergent) run a full tank of fresh premium gas though her (over a week so any deposits in the system can wash out), then try your test. Also check the head bolt torque during the week of running. And change the oil back to whatever you prefer to run in it after the week. Just another opinion


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I got 65lbs in the first three cylinders and 55lbs in #4 on a cold engine wide open throttle.
My engine is all stock including the head.
Idles smooth.
 
The engine does not look like a new rebuild. The truck had been sitting in a garage with a 2003 inspection sticker on it. Fall of 2013 it saw day light and had limited use until Fall of 2014 when I purchased it. I plan on putting it on the road next Spring.
 
So if it appears the engine has sat for quite awhile and will now sit till spring, I wouldn't mind seeing quite a bit of ATF poured in the 4 holes and let it work its way thru the rings and the cylinder walls.
 
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