Here are the rod journal to shell clearances. White coded shells, they give the loosest fit, are recommended for racing. It seems I installed red coded shells based on measurement. The damaged shell was on the left journal which had the tightest clearances. I always install white shells and my records say this. Maybe the shells I installed were mislabeled.
The machinist showed me a special micrometer for measuring shells. It has a flat and a round anvil. This is what I need so I can check the rascals to make sure they are the correct size before I install them.
You don't need a special mic to measure inside of a radius. You can get balls to attach to your existing od mic so that it can measure on a radius. You then only need subtract the diameter of the ball. In a pinch, a ball bearing and some tape gets the job done.
You need to be very careful when measuring the thickness of "tri-metal" bearing surfaces. The plated, overlay, lead/indium layer on Vandervell/Mahle Motorsport bearings is easily dented and can give an erroneous reading. The bearing manufacturer calls this: embedability. It is to trap foreign particles in this layer. On the other hand, bearings made from Clevite 77 material have a much higher surface hardness.
The best method I have used to measure bearing thickness is to use a special micrometer with a flat anvil and a ground rod. In a pinch, a regular micrometer and a hardened and ground dowel pin can be substituted. I tend to use a .250" or a .500" dowel pin to make the subtraction math simple. Industrial supply houses occasionally list them as "die pins", for stamping dies. They are typically available in std size, +.0005" o/s, and +.001" o/s and various undersizes, just to keep it complicated. I have a buddy who does centerless grinding of gages, for tool and die machinists. I get any size I need from him.
Fordboy
I would think so long as you used the clutch on the mic you would be good. We do babbit friction bearing repair at the shop, and while you do have to be careful it's not THAT fragile. Then again.. when you're doing it every day it always seems more simple. The issue I have with using roll pins is that they are a BASTARD to hold in place while your trying to find the high spot and get a good reading. That said spreading the force over a wider area is always superior.
At work I have a calculator in my pocket at ALL times. I've found one I really, really like for doing machine work for both their durability and just the right selection of functions, multiple memory positions (so you can say, store the pin diameter in a memory slot and recall it to the tenth with a button push, makes it hard to get it wrong) and a scroll back function so you can scroll back and double check the numbers you punched in as a second check of your math. TI-30XIIS. They are only like $25, and I get a year out of them between stupid incidents. Generally they get smashed, droped in a bucket of oil, set fire too or some otherwise mangled or maimed before the batteries go dead.
The plastic holds up well to hot chips, oil and coolant though so that's a big plus!