Who has done this?
I've replaced rod bearings with engines still in cars but I don't think that I've replaced a full set of main bearings before. Rods are easy, pushing the rod UP a slight amount allows adequate clearance to slip the top shell out.
The mains though...it isn't as if you can pull the crank away from the block to give the upper shells room to move.
20+ Years ago I did replace a few bearings in a Honda 1.5 4 cylinder but that was a LONG time ago.
I've changed rear main seals in LA and Big blocks. That upper section just rotates around when you push it with something soft enough to not scratch the crank should it slip.
I'm thinking that a firm plastic stick could be used to clock the bearing shell a bit, then a pick could be pressed on the back side of the bearing that sticks out, slowly rotating it until it slips out.
This car.....
View attachment 1716305152
Looks like crap but is a fun dirt road drift car. It has a fairly stock mid 70s 360 with a stock bottom end, a 280/474 Mopar cam, #308 heads, a Weiand intake and Holley 600 carb. It runs strong but the oil pressure is low. The cheapo aftermarket gauge actually reads zero at idle. During a cold start, my 440 Power Wagon reads 70 psi. Another car reads 50. This was at 25 at fast idle. That is simply too low.
I'm hearing some rattling inside. I pulled a valve cover and let it run. The rocker arms are somewhat quiet. It seems like it is down low. I thought maybe the oil is just tired and maybe thin but it is clean. It does have a little smell of gasoline but I can't be sure. It has literally been YEARS since i changed the oil. The car sits until I decide to bash around dirt trails, then I park it for months. I might change the oil and see if that increases the pressure and eliminates the knock/rattle. If not, I can pull the pan and check the condition of the crank bearings.