Here's a simple question for those who know and I realise that I could go and unscrew one to measure it to find out, but can anyone tell me if the thread on PR4/A oil filter housing cap is parallel or tapered?
Isn't there a taper either on the cap or in the case?It's the flange that does the sealing, aided by a good jollop of non setting sealer.
I believe that the flange has a tapered face to seal into a tapered lead around the female thread.