Posted by MicahKev (IP: 152.205.243.9) on July 17, 1999 at 22:17:16:
In Reply to: ENGINE "KNOCK" posted by DAB on July 17, 1999 at 10:00:33:
I a '71 that I put a 250 in. I removed the EGR valve, added headers and a Weber carb to get better air flow. I had a lot of problems with pinging at acceleration and while trying to climb hills. I also thought it was a problem with low octane and timing. I poured a lot of money into octane boost and super gas with no effect. I adjusted the timing also without any effect. The problem was that the main jet was too small causing the engine to run lean. This will cause the pining along with overheating and burning of the valves and valve guides.
Often this can be caused by an EGR valve that is not working correctly. The EGR valve adds exhaust gases to the intake manifold. If the exhaust gases are not being mixed in, the engine gets more fresh air. The carb is jetted for the lesser amount of fresh air. When it gets more than it should it runs lean.
I suggest that you have the vehicle placed on an emission testing machine and determine if it is running too lean or replace the EGR valve if it is equipped.
If this is in fact the cause you need to correct it as soon as possible. It took me a while to realize the problem. I have rebuilt the cylinder head three times. If you start to burn a lot of oil or your spark plugs get oil fouled, the cylinder head neads to be rebuilt.
Let me know how it goes.
MicahKev@aol.com