While travelling down the freeway today at about 85 mph, I lost some of my power- there was no accompanying loud noise or anything. However on slowing down there was indeed a fairly loud metallic clackety sound eminating from the engine.
"Listening" along the valve covers with a broomstick didn't work very well, it was difficult to discern which side let alone pinpoint where the noise was coming from, eminating from all along the top of the engine (or maybe underneath). Anyway, cylinder 6 is pretty dead at 40 psi, all others 135 or greater. Adding oil to cylinder did not help compression at all. The electrodes on this spark plug were, ah, devastated. The center elecrode appeared to be missing and there was alot of (oily) chunky deposit on outer electrode. Removed the valve cover and the cam lobes appear to be ok, along with plenty of oil. No oil in coolant nor loss of coolant that I can tell. While driving, the noise is quietest when I accelerate gently, loudest when decelerating or idling.
Ideas on what the problem is are greatly appreciated, I am just about to attempt to remove the head to check things out. Anything else I should check first?
Thanks, Greg