Hi, this is my first post and I'm really glad this site exists.

Recently got my '77 264, with the notorious PRV6 B27F. At 40,000 miles and perfect exterior / good interior condition, it was really quite the find. After rebuilding the fuel distribution block, replacing plugs, fuel tank, and thermostat, it performs very well with good power and no color in the exhaust. There's a little valve pinging, but nothing extraordinary for an older car.

HOWEVER, I have found coolant in the oil--that grey-brown sludge. It is most apparent under the oil filler cap--in the cap's filter and in the pan just below the filler cap. It's also starting to show up on the dipstick. Oddly, sludge is present in the tube leading from the air inlet manifold to the filler cap. The other tube leading from the filler cap is absent of oil. This makes me wonder if coolant (or water-vapor?) may be invading the crankcase from the air intake manifold. I've noticed that the excess coolant reservoir is tending to burp out coolant onto the hot engine, and wondered if this, combined with the fact that the filler cap had a bad seal, might somehow be related. The temp gauge has remained at or below "N."

Or am I tripping and this more likely your typical head gasket or block seal problem?

Any input from those familiar with the B27F would be most appreciated.