Since swapping heads and adjusting my valves using the "rock" technique, my engine has begin to sound like a quiet well-oiled sewing machine.

The idle is so smooth I can hardly believe it, and after my initial test-drive with the initially noisy replacement M40, the car seems to have settled down to a nice smooth purr on the road. The car starts up easily and shuts off without a hint of the dieseling I had previously experienced.

I'm hoping this will lead to a drastic improvement in fuel economy. I fueled up this morning, so we'll just wait and see (the last tank was again 13 mpg).

So... I know from my experience putting a B20E into my 67 wagon, that the little black plastic disk-caps on the top of the valves is not necessary. I noted that a few were missing when I put my original (but once-rebuilt) B18B cylinder head onto my 1968 B18B engine block.

After my commute today I found some oil leaking out from under the valve cover. I removed my valve cover and cleaned/scrapped the surface and re-glued my nitrile rubber valve cover gasket.

During clear up I found broken pieces of at least two of those bakelite-like caps lying on the top of the head. They were not there before, and I'm missing about four total now.

The engine still runs smoothly and I think I retrieved all the pieces, but these things breaking has me a little concerned.

Why did they break? Valve lash is still in spec, nothing else loose in there. Is this common or "normal"?

Should I remove the other caps? Seems like a bit of a hazard if I'm risking bits of black plastic circulating in my oil...