Update: W-4 / H Farmall Dies When Hot. Rings, Valves, Other?

I spent most of this weekend trying to figure out the reason my W-4, which has an identical engine to an H Farmall, (in case anyone didn't know already) keeps losing compression when it's hot. It will run PERFECTLY when first started and operated, but then as it warms up, it will eventually begin to miss and die. Even if you shut if off before it gets hot enough to act up, it will spin over way too fast (for what a normal 6 volt system would do) and not start without a pull.

Anyway, I started by replacing my valve springs, as they seemed quite weak (although the new ones from Case IH didn't seem all that much stiffer).

Then, I tested the compression and it ranged anywhere from 45 psi to 75 psi per cylinder. I then compared that to my H, which works perfectly, I found that it has 110 psi across the board.

This obviously raises red flags. However, I'm uncertain how to know if it's my rings or my valves causing the problem.

The engine does not smoke at all. It also runs perfectly at high or low RPM when it's not too hot. I would have thought that bad rings would cause smoking and bad valves would have caused a rough idle. I could hear air escaping in some of the cylinders when I had them under pressure to replace the valve springs.

Also, it has a mag, which seems to put out good spark.
Sorry for the long novel of a post, but I'm stumped and I don't want to fix one "problem" only to find out it was being caused by something else.

Any input would be greatly appreciated and thank you for your time!

I would start with a valve clearance adjustment and see what happens. Has worked for me couple of times.

If you're losing air pressure when the pistons are at TDC on the compression stroke either the valves are leaking compression or the rings & sleeves are worn. Is the valve clearance set at .020" cold? Has this engine ever been rebuilt? Hold your hand over the throat of the carburetor while someone makes an attempt to start the engine. If there's very little suction on your is a good indication of low intake manifold vacuum which is determined by good rings, sleeves & valves seating without any leakage. You may need to pull the head and have a good shop to go over it. Measure those sleeves to see if they're worn. Hal

Yeah, I forgot to mention that my valves have been adjusted to .020 when cold and I have new valve springs on there.

A few things throw me off still.

1. The new valve springs are not much stiffer than the old ones, and definitely not as stiff as the ones on my H. Could this be an issue?

2. If the sleeves and rings are shot, shouldn't it smoke? Is it possible that only the compression rings are shot but oil rings are still good?

3. If the valves aren't seating right, shouldn't it run rough all the time?... because it really runs nice before the temperature gets up there.

I'm not questioning anyone's judgment, as there's obviously something wrong. I'm just confused a little by what's going on.

The compression rings may be stuck in the ring lans on the piston. The only way you can determine that is to pull a piston with low compression. When the engine spins freely after it warms up is a sign of low compression and the rings, sleeves and valves are all related in order to have good compression. Your engine probably needs to be completely rebuilt. Hal

Get a cylinder leak-down tester; it will tell you where the air (compression) is leaking out of the cylinder.
Bring each cylinder up to TDC on compression, hold the crankshaft so it will not rotate on it's own, and add air pressure with the tester.
It will show the percentage of leakage and by listening to the escaping air (muffler, air cleaner, oil fill) you can determine your problem without any further disassembly.
This is the best tool in my toolbox for internal engine condition evaluation.

You seem to have an odd problem. You may have valves getting in a bind when hot and closing slowly, but I've never seen that happen.

The valve springs are pretty weak.

I am going to suggest the opening up of the valve gap setting. It is supposed to be .020" cold. I think using .025" would be a test of the valve system as heat builds up.
I also agree with the use of a leak down tester. Get the directions for listening to various locations to determine the compression loss. JimN

Well I have some answers! First of all, thank you to all who replied... in hindsight, I was given some very sound advice.

My Dad was kind enough to take the head off tonight after work (I live a couple hours away from my tractor) and found the rings AND the valves to be shot! Turns out everything was the cause

We have a very trusty tractor mechanic replacing the valves and I'll be installing the new rings this week on my day off... as well as putting a set of new Firestones on it (Yippeeee!).

I hope this solves it all, because I'm out of time off before the big Almelund (MN) show.

Thanks again for all your great replies!

Eric