LA 360 - 0.030" Undersize Main Bearing Clearance Questions

Desoto291hemi said
D4rt ,

Thank you for the cordial response,,,,,I appreciate it .

Almost 3 clearance sounds pretty loose to me,,,,unless it’s a serious race engine,,,,even then 2.8 sounds fairly open to me. .

I try to keep my mains to around 2 ,,,big block or small block .
It helps the oil stay where it’s supposed to be,,,,,and the pressure too .
Have you done a complete study of all your clearance on each journal ,,,,at several different positions ?
If the crank is not egged shaped,,,,I think you should be good .
I have seen some cranks even polished a little different on each journal to make up for other issues .

I have seen cranks that were true even down to the tenth of a thousandth,,,,,now that’s close !
But,,,it takes an expert craftsman,,,willing to do several belt changes,,,,,and a good touch with the pressure .

It sounds like you are trying to do it right and I believe you should have a great engine when you get done .

Tommy

Yep, I checked both the main and rod journals in multiple spots looking for taper and out of round (egg) with a 2-3 in. outside micrometer. Everything looks pretty good in that regard. Not perfect, but within spec based on what I've read. Main journals 1-3 all have 0.0002 in. egg, zero egg for main #4 and 0.0003 in. for main #5. Zero taper on the main journals with the exception of main #5. That has 0.0003" of taper. The rod journals aren't quite as clean, but still pretty good. Egg varies from 0.0001" - 0.0004". Taper is all within spec on the rod journals too. The shaft diameter for the rod journals are within spec too.

Finally got my machinist on the phone. I'm going to bring the rods, pistons, crank and block back in to the machine shop on Monday. He's going to check my work and then we'll go from there. I might swing out to the salvage yard tomorrow and see if I can pickup a cheap crankshaft. There's a dozen Rams with 5.9 Magnums between the two yards near me. I'll have to pull it myself, but with the sale going on, I should be able to get a crankshaft for ~$30 out the door. From what I've read, the cranks in the magnums will interchange as long as I use an LA rotating assembly, balancer and flex plate, which is what I have. Kind of a PITA to pull an engine just for the crank without knowing whether the engine has been messed with or not.