Ordering parts from Speedway/person on the other end of the phone was an ex-machinist who had worked at speedway for years. Conversation turned to flatheads(I have over 55 years experience)with flat-motors and I was the salesman(friend of the buyer) for the French flatheads that came into Texas in the late 90’s. He asked me if I had heard of the Ford OOPS motor. I said I had never heard of them. When he was a machinist in the 90’s, he was rebuilding a motor and ordered new cam bearing as part of the package.He went to install them and found they “dropped” thru the normal bores that held the bearings. The “tunnel” was .020 LARGER than it should have been. He did some research and found Ford had mistakenly cast around 1,000 engines before discovering the OOPS. They manufactured 100 sets of .020 oversized cam bearings rather than scrapping the “mistake”. All 100 sets were purchased by Red’s Headers out of Cali and he purchased a set to complete his overhaul. He said Ford called it the OOPS motor; something I never heard of!
Back "Inna Day" things like this happened. Another example of this was with Mopar flathead sixes in that you had to be sure of rod and main bearing sizes, as some came with undersize journals and corresponding bearing inserts to match. Sometimes it was only on some journals.
Don't know about Fords but my old boss rebuilt a Rambler 6 for his MIL and came to find out that it had oversize cam bearings from the factory. Chased low oil pressure until he figured out the cam bearing issue. Installed a set of oversized bearings and all was good.
Old Henry didn't believe in letting anything go to waste. That's why parts were used until they were used up, even if they were for last years model. Over the years, I've ran across things that shouldn't be a certain year model, but were, just for that very reason....
Interesting and easier to make a oversized bearing then scrap a bunch of blocks. Thats what I call “plan B “ to a oops
The auto manufacturers regularly repaired mismachined blocks and heads. When I restored the Orange Crate Olds engine I discovered that some of the original lifter bores had been bored .020 oversize by the factory.
I reasoned that out of a thousand or so Motors, maybe 10%or about 100 would be overhauled to make a few more miles. Don’t know for sure,just a guess!