There has been some discussion lately about using full groove bearings.

Below is a pic of a full groove main cap bearing. These were in my used 401 when I tore it down for rebuild. Also shown is the number 7 rod bearing that had spun, the stock nylon timing gear, and a blown out lifter.

Note the chipped nylon teeth at the lower right corner of the timing gear - many more teeth were chewed up than those shown in the pic. IMO this is the number one cause of oil system failure. This stuff gets ground up and distributed throughout the system and clogs up oiling passages. In this case I found nylon stuck in the pan pickup strainer and elsewhere - I suspect it had everything to do with the failed lifter and spun #7 bearing. Engine was full of dino oil sludge as well. Sorry guys, but a valley bypass line is not going to fix what caused this bearing failure.

All main cap bearings looked like the one shown and all other rod bearings looked normal for wear, no signs of scoring on any crank journals including number 7 rod. Crank cleaned up 10/10 under.

In contrast, my 390 had been run on Mobile 1 most of its life (115k miles), looked clean as a whistle, and bearings looked good for another 100k miles. The 390 also had full groove main bearings (looked new).

I'm really torn about using full groove bearings. I know they provide half the oil film strength of non-grooved cap bearings but these seem to have held up well under the circumstances, and I like the idea of oiling the rod journals through a full 360 degrees of crank rotation that full groove bearings provide.

I already have a set of new Clevite half groove bearings for the rebuild - but.....

PS: You can see an oily gritty paste stuck to the spokes of the timing gear, the top of the left lifter, and down in the groove of the main bearing. This is the kind of stuff that was cloggin things up.