Mystery pistons?

I have four Aluminum overbore pistons (3 7/8") out of an F20 I have started working on that I might or might not need to replace depending on how successful I am getting the rings off of them. One is eroded on top due to me screwing up not cleaning them thoroughly enough after a short dip in muriatic acid a few years ago but might be usable. I have no idea who made these pistons. They have three compression rings and one oil ring with the top compression ring being narrower than the next two compression rings. Inside the piston skirts is the letters MWM or WMW on one side and then the numbers A1002 on the other side. The rings are stuck very tight. I got the rings off of one piston in pieces but It took an hour and I still put a few small nicks in the piston in the process. The pistons were rusted and corroded in the bores very tight too but I don't see any damage on them from pounding them out after soaking them with every magic elixor known to man for a year. No water had sat on them as this tractor was shedded. I am not worried about finding rings, I'm sure Hastings can fix me up with new ones, but if I have to replace pistons I might have a harder time.

The sleeves and pistons have very little wear and the piston sidewalls are nice and smooth yet. The crank and crank bearings are fine.

Does any of the information about the pistons ring a bell with any of you guys? Of course the MWM makes me think of M&W but it might not be from that company. Thanks

Your question got me to thinking . Many, many yrs ago, I had some alum. pistons for M -M tractors that were marked WMW. Someone told me that stood for White Machine Works. No sure where they were located, but mite of been somewhere in Wis. HTH, clint

I Googled White Machine Works in Eau Clair Wisconsin. They changed their name to Strataflow in 1941 and it appears they made valves for submarines when they started business in 1941. I have the impression they stayed with making valves but I didn't read into their product line very far.

What about soaking them in a product like CLR ? I have used the works toilet bowl cleaner on rusted stuff before but it will eat alum.

Will CLR eat aluminum? Maybe I should try it on some scrap first. I have thought about vinegar since most of the problem is white oxidation from steel on aluminum. When I cleaned out the ring grooves in the first piston I scraped out that oxidation. The sidewalls of the sleeves have a combination of rust and white stuff on them.

If those pistons are aluminum, just heat them with a propane torch & let them cool. Do it as many times it takes to break the rings loose. Use atf when they are hot too.

I heated them once then using PB blaster. Maybe I should do it again? How about heating them and dipping them in a can of ATF? It looks to me like that white oxidation has squeezed the rings in tight.

fixerupper we have a f 30 been sitting for over 50 years an now would like to fix her up the motor is stuck got any ideas on how
to get the engine to turn over i have dumped diesel fuel in it a year ago with no luck your ideas will greatly be appreciated I
would soak the pistons in diesel fuel for 3 months then see what happens

If your F30 has been sitting that long you are going to have to bite the bullet and tear it down. The pistons are probably rusted too tight to let the diesel fuel wick down alongside the pistons. It's probable the valves are stuck too. Where do you live? If you are in a dry climate like Arizona the rust might not be real bad but if you live in a humid eastern state the rust will be worse.

bteny,If it's sat for that long,and the diesel hasn't helped.You need to tear it down tear down.The diesel trick wont work on something stuck that bad,or long.I know you dont want to hear that,but that's just the way it is.I have an MD that sat on the side of a mountain at 9000ft for 35 years.Stuck hard. Soaked for a year too.No movement. One piston was rusted solid.Had a can over the muffler,too.

Keep at it. The aluminum expands more than the cast iron rings, so it will give a little each time. I have done this with Wisconsin pistons & got the rings loose.