Fully groves mains
Bob,
Some BS creeping in here. There is no mention of your crank material, but since you are talking about increased oiling, I assume it is a performance engine & using a forged steel crank. These can be Tufftrided or Nitrided, both extremely thin chemical treatments that are gone if the crank is ground undersize; some have neither treatment & are just plain ole steel...Same with cast iron crank, plain ole CI.
The steel brg shell is as hard as the f/steel or CI. It is a 'springy', hard, steel, because when you insert it, & then remove it, it springs back into shape; mild steel does not do that.
Unless you have some method of accurately checking for raised metal, as I described earlier in this thread, you would be better of not attempting this mod at home.
The crank journals wether a steel crank or a cast crank are induction hardened.
An outline of the process is:
1) crank journals and mains are cut to size + a few thousands using normal cutting tools
2) the pins and mains are induction hardened, basically a heat and quench.
3) the pins and mains are then ground to size.
The reason they are ground is they are too hard to be cut with normal cutting tools.
The backing steel on plain bearings is dead soft. The backing steel is soft so it conforms to the round shape of the block bearing bridge-main cap or the big end of the rod.
If one wants to verify this, take a sharp hand file, place it on a edge and using hand pressure run the file across a crank main or rod journal. The file will zing across the surface because the surface is hard.
Using the same file and the same pressure, run the file across the steel backing of a plain bearing half round. The file will cut into the steel backing because the surface is soft steel.
Note: on crankshafts, only the machined surfaces and nearby radius of the pins and mains are induction hardened, the counter weights and machined flanges are not hardened.
it is true that nitride and tuftride treatments are thin, but those treatments are typically used on HD crank applications and not automotive applications, even automotive preformance cranks don’t always get those treatments.
Ask your local crankshaft shop if they send all crankshafts out for nitriding or tuftriding after the journals and mains are cut undersized. The answer will be only if the customer pays for it.
That is because the tuftride - nitride adds additional hardness to the very top of the already hard induction hardened zone. The induction hardened zone goes into the crank .060 to .080 thousands, that is why one can have .010, .020 ground from a crank main or pin and not have to re harden the main or journal.
