Late A cylinder wear

Mike(NEOhio)

Well-known Member
Location
Newbury, Ohio
The job started with replacing the manifold gasket. Two studs are still stuck and may need machining the gasket surface so I pulled the head this week. Everything is in real nice shape and I'm going to get the valves ground. Yesterday I miked the bores top, mid-range and bottom. Most measurements showed .0025 to .004 wear with one place .006 at the bottom of stroke, pistons in. I want to check the mains and rods, I know they're a little loose but that will wait for warmer weather. It only shows a couple of puffs of smoke after idling for a few minutes but no smoke running and pulling. I intend to pull the pistons to check sizes and rings. The bores are real clean. I'm trying to avoid mission creep so asking for opinions. Should I leave the rings or re-ring with new standards. Suppose that would depend on how they look and side clearance.
 
I have a 630 that was worm pretty bad. Ran out of project money for boring and new pistols. Scuffed up the more and put new rings on doesn't smoke and blow by is barely a breath coming out. I am cheap so I would do it the same again.
 
The first thing I wanted to tell you is make sure the shop understands " installed stem height". All the older 2 cylinder heads I did at Dana needed to have this corrected! A set of hard valve seats will solve that problem. Questions? J.
 
I haven't looked for an A but I think rings are fairly cheap. Your bores aren't worn too much. When I did my B there was pretty excessive ring end gap (about 1/8") in the old rings. With new rings put in I think the gaps varied between .025-.035".
 
Normally most of the wear in a 2 cyl. is on the top side of the cyl. bore at the top end of ring travel. So this is where you should double check for wear. Are your pistons cast iron and standard bore ? Cast pistons hold up a lot better than aluminum ones like in the below mentioned 630. Those have thin rings that tend to wear and break. An A has thicker rings that hold up better, but I never would reuse rings. New rings used to not be real expensive. Your rods may still be the adjustable babbit style. This would be the ideal time to pop the pistons and install new rings and adjust the rod bearings.
 
That's what I plan to do, Mike. My ser. no. is 671111 so it should have insert rods and babbit mains. I know the mains are loose so rods probably are too. Never rebuilt, was my father in law's and well cared for. I've been around it for fifty years. It is standard bore and CI pistons and from the looks of the bores they should be in real good shape. Any aftermarket inserts I've found are .010 and .020 under but Deere lists -.002 and -.004 in the catalog, if they're still available.
 
I do not think I would put undersize bearings on a crank unless it was turned, good chance it is out of round.
 
Mike, if by chanch you need another set of cast pistons and rings, I have a very good set from my 50 "A". Joe in Chesterland
 
same thing as when doing a valve job on a 390 ford engine heads for example. there is no valve adjustment, you just tighten the rocker arm shaft down. all valve stems must be the same height. chevy for example has individual rocker arms for each valve. each rocker is tightened 3/4-1 turn from zero lash. so the valve stem height don't really have to be the same. as when the valve seat is worn out you will have a higher valve stem measurement.
 
Depends on what you want to do. I recently had the same issue with a 49 A. The tractor was pulling good but on start up would puff a little white. Was replacing the manifold one of the studs broke off, so took the head to the machine shop and found it was cracked, found the white puff on startup. I did not remove the pistons since the tractor still has good power. I did not mic the bore but baced on feel there is more wear in my cylinders than yours. Mine still gets worked hard on occasion just not as long as they used be.
 
pretty sure it is about the valve recession. if you have a higher valve stem hight, then the valve is recessed in the seat which can be worn or ground too much. this decreases the compression. on a diesel , important for starting also.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top