420 engine compression tests

[notmeu]

I recently noticed a small amount of white smoke coming out of my oil filler tube so since we are having some warm then cold days in Pennsylvania I figured it was condensation, especially since I haven't been using my 1956 420 much lately. So I did a cylinder leak down test and a compression test so I could sleep a little easier at night. I had around 113 pounds of compression on the front cylinder and around 110 pounds on the rear cylinder. I checked for oil in the coolant and there was none, and there is no sign of any water or foam in the oil. The leak down test showed a 35% loss in the front cylinder and about a 38% loss in the rear cylinder, both readings were in the low loss side but 40% begins the moderate part of the gauge, there was a lower amount of compressed air coming from the dip stick and the filler tube. The oil pressure gauge always reads HIGH and there is never seems to be any loss of power, no white smoke coming out of the exhaust, it always starts up instantly. There seems to be a small amount of water/condensate on the inside of the oil filler tube cap while it is running. Also I was about a 1/2 quart overfilled in the engine so I drained it out. Which it did seem to smoke less. I also set the valve clearances on all 4 valves. I'm thinking everything is pretty normal for the age, although the piston rings are somewhat worn. Am I thinking correctly or am I missing something? All opinions are greatly appreciated. Thanks for your time in advance!

[DukeofDeere]

Most Debuque tractors should read full if you pull the dipstick very soon after shutdown.
If you wait longer it will read one quart over full due to the filter can draining down.
If this machine has some temp fluctuations from change in weather there will always be some moisture in the crankcase that will take some running to evaporate out. (White steam) nothing unusual. Newer engines have the crankcases breather going back into the air cleaner then carb to burn it off.
The close readings sound very good on your compression test!
Sounds like a strong machine.

Duke

[notmeu]

Just re-did the leak down test and I made the changes on the original posting above.

[DukeofDeere]

What made quite a difference for me was putting in a new thermostat in my '56 420.

Duke

[notmeu]

The thermostat on mine is literally a year old. What temperature did you go with? I want with 160'

[boler76]

I also have a 56 420 and to eliminate the moisture problem I went with a 180 thermostat and a jute bag over the rad for winter operation, they should be run at the top of the temp range to eliminate the condensation in my opinion

[DukeofDeere]

The stat in mine is 180.
15+ years old.
Still have moisture though.
At least it gets warmed up when used.

Duke

[Lavoy]

A lot of the time you will have moisture in the breather cap and pipe, but not in the engine itself. You have hot air escaping the engine through the pipe and breather which are cold, so it condenses there.
Lavoy

[notmeu]

A lot of the time you will have moisture in the breather cap and pipe, but not in the engine itself. You have hot air escaping the engine through the pipe and breather which are cold, so it condenses there.
Lavoy

That makes sense Lavoy, Does the compression tests sound good? I cannot find any information online, or in the service manual.

[DukeofDeere]

In my neck of the woods with all the temp fluctuations there is almost always condensation certain times of the year.
Spring project at my uncles with 40+ antique tractors in cold storage is to open the crankcases and transmissions and drain off the condensation. Usually a cup or more before clean oil comes from around the threads of the drain plug.

Compression test is really good.
Being that close to equal is great.
If I remember right 120- 130 is perfect.

Duke

[Lavoy]

You are within 10% difference, and the overall numbers is good.
Lavoy

[Paul Buhler]

checked my notes, and my 420 has compression of 110 on #1 and 115 on #2. I used an inexpensive rubber cone type tester, so numbers may be off somewhat, but it gave me an idea of the balance between the cylinders. Paul

[notmeu]

checked my notes, and my 420 has compression of 110 on #1 and 115 on #2. I used an inexpensive rubber cone type tester, so numbers may be off somewhat, but it gave me an idea of the balance between the cylinders. Paul

Thanks Paul. I'm surpried that the compression isn't more of a published data for the 420, either in the manual or service manual. If it is I surely missed it!