Some have improved it by using oil instead of grease, with deeper rocker box covers used as oil sumps. The oil, splashed around by the rockers, lubricates all the parts as soon as the engine starts, and drips back down into the sump, transferring heat from the valves stems and springs to the outside. They are happy with it, and engines opened after 300 hours show no valve guide wear.
Josef Rosenberg (Germany) sells the deep rocker cover kits.
or (better):
Phone/Fax: 00492131601394
Though this was a very interesting improvement, it was not perfect. The actual oil level in the rocker boxes was unknown: one had to add oil until it dripped from the overflow pipe, on a systematic basis (typically every 7 to 8 hours, the sumps being designed for 10 hours maximum). This was a tedious and dirty work, with locking wires to remove then replace and a difficult access to cylinder 1 inside the noseball. Moreover it sometimes proved useless as almost no oil was to be added, and sometimes it made you consider that you'd better do it earlier, probably depending of your ratio of aerobatics and the condition of your rocker axle plugs and push-rod tubes seals...
I tried to improve it further: I aimed at checking the rocker boxes oil level at a glance at each pre-flight check, and if necessary - only if necessary - add the requested oil quantity in seconds.
I made a visual gauge from clear Teflon tube, and an easy-filling pipe. The Teflon tube is the same as in the oil circuit, without the braid so that one can see the oil inside. It comes from the previous outflow pipe (drilled at its base to let oil in) up to the previous refill fitting (replaced by a new one, lathed out of a 10 mm brass hexagonal rod).
To add oil I replaced the rocker axle plug by a banjo fitting at the rear of each cylinder: happily, very light aluminum 20° banjo JIC fittings can be found with the same thread as the original plug. JIC aluminum plugs tightly close them.
Now:
- Checking the oil level is easy, even in cylinder 1
- Access to the oil filling pipe is easy, even in cylinder 1
- Adding oil is easy through the filling pipe, using a plain plastic medical syringe (even better with a female JIC fitting-equipped piece of tubing added to the syringe)
- The filling pipe is easily plugged tightly: finger-tighten the JIC plug, then add 1/8 wrench turn. It will neither get loose, nor leak.
Waiting for warmer skies, have a good workshop season!