Hi all

Good news.
I found the problem. I took my car in for a tappet ajustment because one tappet was making a bit of noise for some time.
When I got it back. The mechanic informed me that ALL tappets were too tight and one was too loose.
He ajusted them correctly. (This is the mechanic who helped a Datsun racing team in the early 80's. They raced a 1200GX).

I also discovered that my tappet cover breater pipe was blocked due to a sharp bend that made the pipe colapse and shut if off. I replaced this pipe. And very important. I went to a exhaust shop to put on a 2" freeflow exhaust as mine started to make some strange noises from the box.

Through investigation, the exhaust box that was removed was starting to cause blockage inside making it difficult for the car to breath. The engine made alot of noise when revved hard past 5000rpm and it also struggled to rev to 6000rpm.

The results.
Car is now as silent as a mouse.
I can rev it to 6500rpm without noise coming from the engine asif someone is strangling it. And it is much smoother than it was.
I cannot believe that such stupid stuff could have caused the problem.

I also discovered that the vacuum advance pipe was cracked near the distributor.
So bad that I doubt there was any vacuum advance taking place. This pipe I have replaced and must still test if it is going to make a difference.
Does vacuum advance make a big difference?