914-4 2L #3 rod bearing failure Options

[Driver174]

Rod bearings 1,2 & 4 look good, but #3 not so good. This engine has approximately ten race weekends sense it was rebuilt. Has anyone seen this issue?

[Driver174]

Had this happen to my rod bearings twice even while running Brad Penn, a tuna can, and 1/2 quart over. What I found was happening (based on logging oil pressure) was the oil was not draining back fast enough. If you don't want to go dry sump (which I did) you can try blocking off the head vents and enlarging the case vent. The idea is to keep the heads at a higher pressure than the case to increase oil flow (return) back to the case. I run a -10AN line from the chimney to a cheap breather.

I'm using Brad Penn as well in 20W50 viscosity. Is it normal to run this thick of oil in Type IV's?


An AccuSump was suggested in an earlier post, would I benefit from one?

[ChrisFoley]

I'm using Brad Penn as well in 20W50 viscosity. Is it normal to run this thick of oil in Type IV's?


An AccuSump was suggested in an earlier post, would I benefit from one?

20/50 is appropriate in warmer climates.

The downside of an accusump is the recovery period after a long sweeper, where pressure to the bearings is diminished while the accusump refills. They're really only helpful for up to 2-3 seconds of oil pickup exposure.
The oil vs air volume inside the chamber must be carefully balanced or the accusump will be of no benefit.