Are these pistons OK to reuse?

pburchett

Member
1955 Ford 640 134 ci engine.

I started refreshing my dad’s old Ford tractor. I have owned it since 2004 and never had to do much to it except for maintenance. I redid the rear axle seals and bearings, hydraulic piston pump, lift cover, PTO, front axle pin/bushing, spindle bushings and repacked the front wheels plus I have been cleaning and scraping grease for a paint job later.

I have worked on both sides of the engine as I dreaded that portion. Since the clutch was on its last adjustment I split the tractor for inspection. I now need a clutch, pressure plate, main bearings, and rod bearings.

I now need help inspecting the pistons. They are stamped STD and do show some signs of wear but I do not know if they just need new rings or if I need new pistons, wrist pins, and sleeves. I have not taken any measurements yet.

Going on visuals what is the consensus of these pistons? I tried to take photos of the worst looking portions.

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If I need new pistons I might as well replace the sleeves. If I replace the sleeves I will shrink them with the welder.
I found some piston kits on eBay “BUT” they are starting to rust so I don’t know if they are usable. I don’t mind cleaning rust to save some money but don’t want wrist pins that would give problems later or sleeves that I am unable to drive into the block as that would defeat the money savings. What are the thoughts on these?


KIT 1

KIT 2

KIT 3
 
The pistons have been running in worn cylinders. If they were in an engine with no available parts I would use them in new
sleeves that they fit. It needs a kit. A slightly rusted kit when cleaned up will work. Pistons don't rust. If the rust has
pitted/flaked, that deal is bad. I would go for the slight rust if the price was 1/2 of new. This site sells very good kits.
Jim
 
I agree, your pistons could be reused if u had to. the top ring land still appears to not have too much wear also. you could stick a feeler guage in there with a new ring to check , plus stick a new ring at top of bore to see how much ring end gap you have. spec is .003-.004 for every inch of bore. plus compare with the old ring to see the difference, which will be more.
 
If the sleeves look as good as the pistons and taper is with in tolerance I would just put rings in it. If the sleeves have a taper then would change it all. The skirts are more of an issue than that little bit at the top. If the skirts are worn the piston rocks back and forth in the sleeve allowing the rings to wear in a bad way.
 
pburchett, in my experience, what I intended to DO with the tractor after I finish "fixing it" would dictate what I did to the engine. My opinion is that the piston shown would be more than adequate for puttering around in a parade, pulling a trailer to the woodlot and back, plow a few gardens with, etc. Were I going to work 100 acres of ground, plow, plant, and so on, I might rebuild it. On the other hand, I might do the minor "in-frame" and rebuild it next time. It just really depends on what you plan to use it for. In either case I'd make sure the pins weren't too "wobbly." gm
 
Ask yourself, you've gone to that much trouble getting the piston out. Assuming new pistons are available is it worth the risk to have to do that job again?
 
I went out to the barn and run a hone down the piston sleeves a couple of times and done some measuring. The results are below.
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The piston bores have a 0.075 average taper from top to bottom.

The ring lands have an .0025 average gap between them and the ring.

The piston ring gap is all over the place. From 0.032 to 0.068 Specs on the ring gap is 0.002-0.003.
 
plus it depends on what u are using to take these measurements... the average guy does not even have micrometers to do this. also the ring end gap is .003-004 per inch of bore, so on a 4 inch bore the gap can be .016 not as you said ? .002-.003. you take a new ring and install it at the bottom of sleeve where no wear takes place then move it to the top under the ridge and check the difference , this gives a good idea of wear when you don't have measuring tools. but from what I see it needs sleeves and pistons if it will be a regular work tractor.can get away with rings if it is just a yard chore tractor.
 
The tractor will just be used gently around the house. I have a Kubota MX5200 that we use for the work. The tractor will never be a beautiful as she once was, but I could not stand to see her sit around in poor condition. I will just get new sleeves and pistons. Might as well make it as good as possible since I got it torn down to the bare bones.
 
(quoted from post at 17:53:22 03/17/19) I went out to the barn and run a hone down the piston sleeves a couple of times and done some measuring. The results are below.
mvphoto33005.jpg


mvphoto33006.jpg


mvphoto33007.jpg


mvphoto33008.jpg



The piston bores have a 0.075 average taper from top to bottom.

The ring lands have an .0025 average gap between them and the ring.

The piston ring gap is all over the place. From 0.032 to 0.068 Specs on the ring gap is 0.002-0.003.




I think you mean 0.0075" taper from top to bottom, which is way too much!! If this is sleeveless block it would need to be bored 0.010 oversize at least to have a bore with no taper.
 
When I tore my 9N Ford down 15 years ago only reason I got new pistons was the sleves were showing a lot of ware and big thing was a knock dealer said was wrist pin So with that needed new pistons. Later when I was starting to put back together again I found out the knock was too long a bolt in distributor and it was hitting the ridges on the timing gear. If I would have known that I would not have bought the new pistons, just the sleve and rings. When you don't know better and told it was wrist pin to piston fit making the knock I just went along with them. Years ago I rebuilt a Kohler 241 engine the rings were stuck in piston grove, The cylinder wasscored so bad I was told it would never run without a bore job and new piston. I cleaned it up on piston and cylinder best I could and it ran mowing yard for several years untill head of piston broke off and that could have happened with a new piston as well.
 

Those pistons are junk trash them we are not living during the depression if you gotta use them I can answer you next question after the re-ring job as to why you have piston slap/knock and oil usage...

While there have the rods reconditioned both ends...

On several of those pix the oil control rings are worn slap arse out... Its a well worn engine get over it fix it right one time the first time..
 

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