I was looking at a friends El Camino today with a 454. It has an HEI distributor in it and when its running it has a pretty loud knock. Sounds like a lifter but, it appears to be coming from the distributor. I could even hear it when it was being turned over before starting. Sorry I don't know any details on the internals of the engine but, I thought maybe somebody has had a similar experience?? Any ideas?