Are these know for retaining oil ?

I have seen a few on bikes and in cars with an external drain back to the sump ?

Useful addition? Waste of time ?

ive also seen this mod done and was wondering the same as Jon. Anyone know?

jason

I believe it may work the the other way round to release pressure from the crank case.

'Busa heads can retain 2L of oil in the head when cold or revving hard. Putting a -8 drain in the left hand side back down to the sump or crankcase breather can release up to 3 bhp.