I removed the left-hand main bearing outer race.  The bearing bore in the case has some very unusual defects.  I’ve never seen this before. Have any of you ever seen anything like this? Totally weird.  It’s definitely not a crack.  You can clearly see the bottom of the defect.  Something has been going on here.  BTW, that’s a steel insert that has been cast into the aluminum case.  They did a beautiful job of casting the aluminum around the insert.  If it hadn’t started to flash-rust, I probably would have never noticed the steel insert.

8/25/23   I think this was caused by the outer race turning in the bore.  The inner race had failed and I suspect that it would grab the rollers and cause the bearing to bind up at speed.

Looking at the outer race I don’t see any clues.  Something tore up the shoulder in the left-hand main bearing bore, but it wasn’t the outer race and there are no indications that the outer race was turning in the case.

The case bore for the right-side main bearing has some unusual indications too.  These indications don’t look anything like the left side main bearing bore.  Again, I have no idea what these marks are all about.  Any of you ever seen anything like this? I found some literature on the internet that suggest tracks like this are caused by vibration.    I guess they could be the results of vibration.   The excessive crankshaft runout certainly caused a lot of vibration, and I’ve been running pistons that were significantly heavier or lighter than stock (that didn’t help).

The spacer that resides behind the drive pulley looks unusual.  There is a ridge around the circumference of the face that bears against the inner race of the output shaft bearing.  I wasn’t sure if that was normal, so I asked Dave if he had any spacers to inspect.  Dave’s spacers don’t have a ridge.  Then I found some spacers in my junk and none of them have the ridge.  Looks like the output shaft has been flexing and the resultant cyclic stress is causing the spacer face to fret away.  The ridge is formed because the inner race of the bearing has a large radius, so the spacer doesn’t contact there.  As Armen says, “you find your limits by exceeding them”.

You can see that the inner race of the left-hand output bearing also shows signs of fretting.  Also note that the bearing is sealed.  That’s an important feature.  The seal forces the pressurized oil to go through the hollow output shaft rather than just dribble through the ball bearing.  That oil lubricates the gears that run on the output shaft.

But once the bearings are removed, you will see that each has a seal on the outboard side of the bearing.

And this is the oil feed hole for the left-hand output shaft bearing bore.