I just swapped from Erson to Harland Sharp rockers on race W2s. They oil through the head just like a standard LA head. The harland sharp stuff is very nice although not cheap. I had to re-shim the side clearance on one head several times to get the side clearance right and the other side bolted right up. When I asked them about extra shims etc they gladly sent shim kits to me. Good product, good service.