When did Ford use 13/32 bores on the tappet?
I don't find any evidence that the push rod ever went or had smaller than, 7/16" (14/32") + option of 1/64" OS. in parts books.
Frank, they made 'em. I've run into a couple of blocks with them in my travels. The one I'm working on right now is a 1918. The holes are 13/32" and have never been sleeved or modified as far as we can tell.
I've seen cases where the tappet boss itself was replaced with a separate boss kinda like a replaceable valve guide, but not a smaller lifter. And this appeared to be a factory replacement.
All the same eh? Not.
Tom, may be a mystery never to be solved ??, checked several parts books in your time frame, late 17 though 18 and early 19, no change from 7/16"
I worked on two different blocks just in the last year that I had to ream to standard. They are out there. I would imagine that factory issues occasionally produced undersize tappets and they just used them up.
You would think it would play havoc on the production line, the blocks are drilled for some 40+ holes at once. To stop and set up a run for a few blocks for undersize tappets doesn't sound like Henry's style, but seeing that a few are out there, anything to save a dollar, well that's Henry's style.
There were all sorts of non-standard mechanical parts, repairs, and fixes. I have heard of people doing research at the Benson Ford and finding prints for various “nonstandard parts” that were made to salvage other parts that are undersize, etc.
Ford did re-work many parts and use them up.
I believe that tappet guides were broached, all eight at a time and not combined with another operation. Ford had dozens of machines for most every operation that were all the same, so occasionally setting one machine up with 8 undersize broaches to salvage 10,000 tappets likely was a good cost saving measure.