Ongoing investigation …oil

Having now plugged the oil vent holes in each rocker head and waited for the massive cold snap to go …and the rains that followed to ease …I’ve finally managed to get out and get 2 ground runs in to check for ongoing oil leaks.

Block and surrounds all degreased and dry I run her up to 50’ then 60’ oil temps .. then ranges from tickover to 2,000 rpm then up to 2,300 before the brakes creak at me that they can’t hold on the wet grass.

Taxy back from the power check area and whip off the now warm cowls to check

3 of the 4 cylinders are showing signs of oil smears and even drips starting at the base of the push rod guide tubes .. on checking the Jabiru maintenance manual these have a double line of rubbers as they locate into the block .. rubbers 11 and 17 in the diagram below as it exits part 13 .. the adaptor

It’s cold outside ….

I have noticed how much colder it is living up in the winter wilds of Norfolk … and the engine doesn’t burst into life as rapidly as she used to … ok it’s still within say 6-8 revolutions … but used to be 1st or 2nd

Ok .. it has been really cold … but this coupled with reading how Jabiru engines configured in a tailwheel aircraft ..mean that at low revs and cold startups .. the oil is sitting in the rear of the sump and may not get ‘efficiently’ to all the parts that it should

In fact an Australian article went as far to say that the front rockers may not get much lube at all in the initial stages of starting and warm up

Ever, and now MORE conscious of the engine (following the rebuild), I’m keen to be aware of more than I was before and so invested in a heater I saw on Machine Mart to allow pre warming of her in these cold cold months

You know that problem .. you look at something in a picture .. expecting it to be much smaller in real life .. heater duly ordered and delivered and it’s way bigger than I’d planned ! … I’d planned to make a neat little hanger and cowl to hook on the prop and direct nice warm air directly to the sump base and fins.

He heater is about 15” diameter and pretty chunky ! Great for warming me whilst I do the rocker cover removals but not quite petite enough for the ‘hang and blow’ design … will resort to plan B .. the Oratex heat gun in a cradle and running low speed

Anyway – following long discussion with my engine specialist .. we have decided to block off the pre drilled rocker breather holes (these were a mod when hydraulic lifter valves were in use)

I’ve moved from hydraulic to solid lifter … so one suspects you probably need to reverse the mod ! And… after 4 shortish flights … that’s what I’m doing …. Stop spraying oil and electrics with oil over the bulkhead !

The small grub screws were provided and the special Loctite Si gasket cement ordered and then warm the hangar up .. degrease everything and apply and screw in place

Each head has a small hole angled upwards and egress into the fin heads
Not bad at about £9 for the tube .. small self tappers provided
Job done
Next .. test what effect this has .. ground run followed by circuit up to 3,200-3,300 rpm

The useful see through rocker cover will let us run it and see exactly what the oil is doing inside the cover …it’s good to make sure they are getting fully lubed and the return flow …not under pressure, goes back down the pushrod guide tubes into the sump.

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