Non mopar-I wouldn’t believe it if I didn’t see it. I’m reringing a motor for a friend it’s a 1950 Ford 8N tractor. I took the rods and pistons out yesterday and the bottom half of the bearing was stamped 030 and the top was stamped 010 I can’t believe it was running and probably was this way for a very long time. Any idea why someone would do this?

it is VERY common to find an odd mix of journal sizes in these engines. but different size half-shells on the same journal , never seen that one before, haha that's funny.

these engines turn relatively slow and usually make good oil pressure , but not something I would recommend.

Paul

I mix standards with .001 to creep up on clearance when needed. Never an issue for my stuff.

X2, Ford factory manuals for the “Indy” 255, “Le Mans” 427, and “Trans Am” Boss 302 recommend this procedure.

I had a crank polished, rods sized and machine shop sent me home with 4 standards and 4.001 for the rods,.001 go in top half, been together for 30 years and 114,000 miles.

My Uncle Tony when he was building those SCCA 302s back in the 60's-early 70s it was common practice to "make the upper rod loose" by .001 and the 427FE's if it was going to see high RPM 5500+(lol High RPM) the rods were .001 loose and for the 427s with a 428 crank he would also make the lower mains 2,3,4 loose by.001, idea there was if the crank flexed it there would still be some film.
Every Engine I have ever built has had the uppers loose by .001, some of the 6.1 hemis I've done lately have also had #2,3&4 main lower loose by .001

It's that old saying, if your engine is loose only you will know, if it's tight everyone will know.

A lot of modern engine (at least on the Chrysler side) use a standard bearing half for the block, and different letter or color bearing halves on the caps. I think Honda does this, too.