1993 Del Sol
Great, I knew I wasn't crazy 18 years in the game. I had a friend who spun a rod and decided to just stick in oversized bearings at home, then called me complaining the block was making a really messed up noise lol.You are correct, its uncommon to just slap in oversized bearings and roll haha, unless you had prior knowledge of the crank being turned.
Machining or polishing the crank for new bearings is assurance the journals are straight and flat, and a standard rebuilding practice, because the new bearings going in will be very flat. Even if the crank seems flat, it could vary if its been used and abused before, meaning your measurements of oil clearance might show one reading in one spot, and another somewhere else.
Keeping things even and flat across the board is usually the goal when choosing oversized bearings. The machinist will cut the crank the right amount to stay within OEM spec oil clearance while using the oversize bearings.
Rule of thumb: if the crank has never been turned before, yet your oil clearances are way out of spec and requires the thought of oversized bearings to make up the slack, the crank needs to be turned, and the proper oversized bearings selected to achieve the proper oil clearance.
Just slapping in oversize bearings on a crank to bandaid oil clearances is exactly that, a bandaid, with no guarantee of flatness. It honestly should be turned at the machine shop, and oil clearances restored the correct way, unless of course you have prior knowledge of the crank being turned and it hasn't been used much.
My 2 cents
As for the oil cooling I still want to hear his explanation on that.. Who knows? He might just know something we don't, I seldom dismiss an idea just because it seems foreign to me