Do valve job or leave good enough alone?

Brooks E. · Dec 2, 2017

Good morning, I have a '51 model A that had sat for a few decades before I got it. After doing what it needed to get running, I decided to tackle
the job of replacing the exhaust manifold. It was cracked on the LF corner, the only hole that's not solid all the way down. I got the manifold
off, found some minor pitting around exhaust ports(no surprise there), but the ex ports are about .020" lower than the intake ports. I've been
filing on it and it's got a good enough surface that I believe it'll seal up. The engine makes 60 lbs cranking compression on both cylinders,
doesn't blow blue smoke, doesn't overheat.

My dilemma, I own a cylinder head shop and could do anything the head needs, including milling the HG and manifold surfaces. What might I discover
if I remove the head besides pitted cylinder walls, possibly broken head studs, pitted deck, etc? I really don't want to get into the bottom end to
do cylinder work if I find something I don't like.

It's not a show tractor or even a restoration, just a project I took on after my great uncle died and left this in his back yard.

Thanks

erskine2017 · Dec 2, 2017

That is very low compression unless it is an all-fuel tractor. If you own a machine shop, why would you even consider not doing a valve job and putting in new piston rings?

BushogPapa · Dec 2, 2017

I would want to run it , use it and see if it needs more work...you may decide to replace pistons and bore the cylinders..

Would be a shame to do it all twice..!

Ron.

John T · Dec 2, 2017

Sure, that compression is on the low side, but if its not an oil burner or overheater or uses/leaks coolant and runs fine and you're ONLY going to use it for light duty and parading and piddling, you can get by a long time absent a valve job and more. Of course, if you go the full route you may run into stud or head or all other sorts of problems (nothing you cant handle, we all have) but likely will end up with higher compression which is great if you're gonna use it hard n long. ONLY YOU can make this decision.

John T

old · Dec 2, 2017

As long as it runs ok and does not use a quart of oil and hour I would leave it be. I have a 1935 JD-B that was my grandfathers and if the engine ever was opened up it would have been while he owned it and I'll not open it up since it runs ok but yes does smoke a good bit but hey it is very old

coonie minnie · Dec 2, 2017

I'd do the cylinder head. A fresh valve job won't hurt anything. If you don't want to go further, don't!

J. Schwiebert · Dec 2, 2017

YOUR compression is even, but why not do a cylinder leak-down test before you take it apart.

Old Farmall Fan · Dec 2, 2017

This would be a good time to stop and clearly identify just what problem you are trying to solve. The answer to that question will help you determine what action to take.

620 John · Dec 2, 2017

Like the others said as long as it doesn't smoke like crazy and use a lot of oil I would leave it alone. Just pulling the cylinder head can lead to a can of worms. I would also check the oil pressure. That can kinda determine how wore how the bearings are.

ss55 · Dec 3, 2017

It could be like just about every other restoration project - a potential money pit if you are not careful. Prices for pre-1960's tractors have peaked are falling. For maximum enjoyment, fix only what you need to fix starting with the simple fixes and enjoy your tractor as-is. Get to know the tractor for a few years before committing big money for major repairs. Buy an shop manual and study it. An IT manual is OK for pictures and a basic understanding, a factory manual is usually much better when it's time to do the actual repairs. Your tractor sounds like it's already in better shape than many. Enjoy it!

Brooks E. · Dec 6, 2017

You're right about the money that can be spent on this kind of project. I've BTDT with other vehicles.

I decided to pull the head and have a look-see. I was down to the head anyway with the manifold off, and getting back to it after it's put back together would be doing the job twice. It actually came off fairly easily, and I was blown away with what I saw. Still some original JD green paint inside the valve cover. There is NO pitting in the cylinders, and this engine was stuck several years ago when this tractor came home. I've been in the machine shop business since 1978 and have seen lots of engines and engine damage. I really expected to see deep rust pits from the elements getting in the ex stack while it was parked under a big oak tree for so long, uncovered. This iron is so superior to any light duty automotive iron used. Every parts I've work on seems to be much harder iron than what I'm used to.

Anyway the ex valves have been leaking (even though I had set the lash according to specs) and it looks like the head gasket might have been leaking between the 2 cylinders. Maybe fixing those will bump that compression number up a little. I might add some more details as the job goes on. Thanks for the feedback.

PS What' that little hole that's on the bottom side of the cylinder about 1-1/2" down from the deck? It looks like a coolant passage.

620 John · Dec 6, 2017

(quoted from post at 06:10:53 12/06/17) You're right about the money that can be spent on this kind of project. I've BTDT with other vehicles.

I decided to pull the head and have a look-see. I was down to the head anyway with the manifold off, and getting back to it after it's put back together would be doing the job twice. It actually came off fairly easily, and I was blown away with what I saw. Still some original JD green paint inside the valve cover. There is NO pitting in the cylinders, and this engine was stuck several years ago when this tractor came home. I've been in the machine shop business since 1978 and have seen lots of engines and engine damage. I really expected to see deep rust pits from the elements getting in the ex stack while it was parked under a big oak tree for so long, uncovered. This iron is so superior to any light duty automotive iron used. Every parts I've work on seems to be much harder iron than what I'm used to.

Anyway the ex valves have been leaking (even though I had set the lash according to specs) and it looks like the head gasket might have been leaking between the 2 cylinders. Maybe fixing those will bump that compression number up a little. I might add some more details as the job goes on. Thanks for the feedback.

PS What' that little hole that's on the bottom side of the cylinder about 1-1/2" down from the deck? It looks like a coolant passage.

Those little holes are for the petcocks. Yours might have pipe plugs in place of the petcocks because around '51 (I think) the factory started putting just plugs in. It's also not uncommon to have the petcocks replaced by plugs if they started leaking.

Brooks E. · Dec 6, 2017

What was their purpose, to drain rainwater from the cylinders?

620 John · Dec 6, 2017

Opening the petcocks relived some of the compression so the engine could be turned over faster if needed. The petcocks were more common on hand start tractors though.

The electric start start tractors could also be hand started (in case the battery was dead) by attaching the steering wheel to a small drive shaft and inserted into the flywheel end of the crankshaft. Opening the petcocks made hand starting easier.

Do valve job or leave good enough alone?

Brooks E.

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erskine2017

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BushogPapa

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John T

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old

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coonie minnie

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J. Schwiebert

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Old Farmall Fan

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620 John

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ss55

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Brooks E.

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