No water or gas in oil so thinking I can safely rule out a head gasket. Engine actually ran the strongest it's ever ran going down the road. Never know there was a problem at all (other than that off-idle tapping) until ya go to stop and the engine would stall (oh, and the mushy brakes).
The oil cap, along with a rubber grommet in the side of the valve cover below the oil cap were actually partially blown out of said valve cover when I lifted the hood, though I honestly can't say I noticed any smoke. With all the crankcase pressure, I'm guessing I knocked a hole in, or at least cracked a piston somehow. It's the zero vacuum condition that has me puzzled. I've never ran across that before on a gas engine. My plan is to pull the guy out this weekend and strip it down for an autopsy. I'll post what I find.
This actually isn't a bad thing. I was planning on pulling this engine apart to get to the bottom of the tapping. The fact that it's so sick now has just really piqued my interest!
Just out of curiosity, how far can the cylinders on one of these 250's be safely bored? It's a 1974 with the non-integrated head if that matters.
Last edited by Dieseldude03; 09/13/2013 2:20 PM.
