Since my engine rebuild, I’ve covered 4000 miles, without problems, but the oil pressure has always been just ok – 60/65lbs normal running and drop to 10/15lbs hot idling. This is within the bounds of the original BMC recommendation, but for a fully rebuilt engine, not so good. My thinking was that it could be the fact that I refitted the original oil pump, having checked the vane clearances and satisfied myself that it was good enough. The choice of living with it as it was, or major surgery was an easy one…..live with it! But last week I was ordering some parts for a spare engine rebuild and needed a new oil pressure relief valve kit (valve poppet, spring and cap) and noticed the additional shim washers along with the advice on adding them to increase oil pressure. Anyway, not being able to wait for delivery, I decided to have a go at fitting shims to my running engine. Access to the relief valve is relatively easy and with a bit of a fiddle I removed the cap and assembly. Firstly I checked the length of the relief spring, which should be three inches…..mine was 1/8th inch short. I found some 1/4inch flat washers and fitted two of them inside the valve, inserted a spare, correct length spring and refitted the assemblage to the block. On start up, the effect was immediate – 75lbs rising to 85 when revving hard. Idling hot is now 30/35, so a great result. I might try removing one shim to drop the max pressure to 75, but I was pretty chuffed. Easy job and cost nothing. Bill.