Contrails ! Jabiru lube fix # 1

Lubrication problems (finally solved...)

Here is the last update on my Jabiru lubrication woes.

Photo Martin L

After some investigations conducted along with Alexandre Patte from Jabiru France, we discovered that the "restrictor plugs" (located at the base of the oil feed tubes bringing oil from the block to the cylinder heads, valves and rockers) happen to be a little too restrictive on certain engine s/n.

Photo Martin L

It was my case. In my engine we drilled a 0.5 mm dia hole in each plug, which completely solved the problem !!!

So my first impression (that the cylinder heads were not getting enough oil) was correct. But contrary to what I was fearing at the beginning, oil feed galleries in the heads are correctly designed.

Photo John Miller

An oil gallery opens above each valve stem, so (provided oil is fed in sufficient quantity..) each valve guide is correctly lubricated and cooled by fresh oil.

Each rocker box is fed from both sides (gentle oil trickle on each valve) and so the oil can lubricate the rockers and their shaft on its way down.

Then no need for oil spray, as every moving part gets oil permanently.

The corrected oil flow can be visualized on the picture at the top of this web page.

Conclusion

It seems advisable to check the oil flow in the rocker boxes by running the engine with transparent rocker covers. If oil does not reach the exhaust valves, the oil flow must be increased at the restrictor plug.

My "custom" restrictor Tee may now no longer be necessary on a taildragger.
I am quite sure that with the oil flow corrected as mentionned, the "upper" heads are equally fed.

I already logged 60 hrs since this modification, and everything works (knock on wood ;-) perfectly.

Martin L