Here's some more info for Bartomas and Pre'68 Dave.
Today I reset the timing and adjusted the idle. The latter is not very important. Also changed the oil to 10W-30.
Knock is still there but does not seem as obvious as before. It's all very subjective so the noise level may not be important. Also, it is non existent when cold. Only when things are really hot does it occur under load at 1800RPM and above. If I go faster it seems to go away.
Do you think it could be the heat riser valve?
Tell you why I'm beginning to think it is not necessarily internal engine related. I live in an area where there is a lab that tests oil and lubricant samples of long term durability test engines. They do this for all the major German auto manufacturers.
As I was going to change the oil anyway, I asked if they would test my oil. They agreed and I just got the results. NO ABNORMAL CONTAMINANTS. Just ash and carbon which are normal combustion by products. The oil had 2500 miles on it but there were no metal (bearing) particles in it.
Now what??
HMMMM
