Ok so decided to have a go at adjusting the valve clearance on the old girl. Followed the manual step by step and made the adjustments in the correct sequence. I set them to .38 mm as per the specs. Put it all back together, got it running and went for a drive. It ran like a complete dog. Took the rocker cover back off and double checked everything and it all seemed fine. After checking everything else and finding no reason for it I started again but this time set the clearances to .48 mm. Is now running heaps better but still not perfect so I've come to the conclusion .38 mm clearance isn't right for my patrol. I have no idea why and want to know how to work out what they should be set to. Any ideas??