Morris Minor Owners Club

I can't see that the fact it's working OK at low temps with thicker oil, means that it can't be having a problem at higher temps when the oil is thinner.
What symptoms would you get if the seating wasn't up to scratch?

By all means have a look..... I suppose it's possible a thread of swarf is straddling the seat - but I doubt it. I often used a ball bearing relief valve in the past if having problems - although not in my current engine.

Virgil,

Did you fit a new oil pump when changing the crankshaft bearings?