Late 20's Ford parts books after the production of T's had finished.
First list is of piston sizes available for Canadian export T's.
Second list is for USA T's offering only these somewhat odd sizes!
Those are for machinists that miss the mark. ;)
Ford (and probably every other manufacturer) has always offered pistons in tiny increments oversize, up through the modern era. This allows a single out of spec cylinder to be used without having to overbore all of them. Or a hone job on all four, measure the cleaned up diameter and order pistons to match.
About all the shops used to have a portable crank grinder too, drop the pan and grind one throw then match up with an undersize bearing to fit. They finally figured out there was more money in a tear down and rebuild rather than fix something. Now days hardly anyone fixes anything just replace it. I'm poor I still have to fix things or repurpose something. KGB
Dad had a shop in Saginaw Michigan from 1946-1991. He had a guy that would come out and cut one rod journal with the engine in the car. It had to be a manual transmission, and it could not be raised on the hoist. He had an electric roller he would put under one rear wheel. The cutting tool had a handle that he held, and follow the throw of the crank. When it was cleaned up, he would go out to his van and make a bearing to fit.
Fast forward. I moved my family to Grayling Michigan in 1998. It turns out that when the crank shaft guy retired, he moved up here and started Carlisle Canoe Livery.
Hi Royce. Years ago I bought a Chrysler 413 motor for a project that I was working on. As the engine had been sitting outside for a couple of years, I pulled the heads to have a looksee. The gaskets were all factory - there was no evidence that the engine had ever been apart. One of the pistons had .010 stamped on it. I checked the shop manual and found that if in minor imperfection existed in the block, Chrysler would machine the cylinder slightly oversize and install an oversize piston marked with the oversize. Throwing away a block is expensive.
OT, but Chrysler would also install oversize lifters in one or more locations in a block if the lifter bores weren't in spec. Several engine rebuilders have wondered why their oil pressure was so low when they didn't look at the stamped markings on the block and installed standard size lifters in the oversize lifter bores.
Here's a picture of a piston in a T I recently removed a head from, ford script .031 OS
Removed these to rebuild, had been in a while.
BMC, when building Morris vehicles in Australia, would stamp a small map of Australia at the start of the engine number, to indicate that somewhere in that engine, some component was not to standard spec. That alerted the mechanic to be on the lookout when doing a re-build. Of course, the customer was never advised of this.
Allan from down under.