Sexton R975-C1 a mess

[LRDG]

Interesting info, David. Thanks.

I see the manual specifies minimum 30 psi at 800 rpm immediately after a cold start. That's pretty low for a cold oil pressure. With hot oil I could see that dropping to 10 psi, and even lower at 500 rpm. That's not much to keep the big ends floating on the pins, especially if the engine is loaded.

Hard to say which domino fell first, but one guess based on the badly worn master rod big end is the master rod brg clearance increased to the point the end leakage starved the articulated rod bearings and they started seizing on the pins. The rods that broke all broke by tearing the big end apart, which looks very thin-walled and weak to me. But I'm not used to engines with 5.7:1 CR and 2400 rpm redline.

The crank feels looser than it should in the rear main bearing so another possibility is that it wore out and starved all the rod bearings.