Chevrolet Repair: 83 Chevrolet van, chevrolet g20, indicator measures

Question
I have a 1983 Chevrolet G20 van with a 350 4 bbl. and 159000 miles. I am the second owner and as far as I know there have been no major repairs other than the transmission being rebuild at about 100000 miles. I'm having problems with the timing and engine power. When I set the timing at the recommended setting, the engine has a major spark knock and no power. I can set the timing by ear, which is higher than the timing indicator measures and it runs strong for about 1000 miles then loses power and starts developing a slight spark knock. I can clean or change the plugs due to carbon fouling, maybe have to reset the timing and it runs strong again. Any idea on what may be going on? Any help would be appreciated.
Tom

Answer
Hello Tom, There are a couple of things to check here. The advance in the dist. Make sure that the weights are free to move....make sure the vacuum advance works and doesn't leak vacuum. Spark knock can also come from a EGR that doesn't work so you might want to check that too. If your plugs are getting a lot of carbon on them then the combustion cambers are too. This will make the compression go up, this along with hot spots in the carbon will make it ping. Hope this helps you out.

Have a Nice Day      Mark