Pobjoy operations
I think it is fair to say that the 'servicing' and operation of a Pobjoy is more akin to a cross between a sewing machine and a small turbine.
The engine was very small and light for its power,but had to live with materials and oil of the period.
Because the oil has to cope with a reduction gear (SAE 50-60) this is not ideal for good flow through a tiny metering system to the top valves.
As mentioned the cowling system would not have encouraged much extra probing,and indeed the valve design (and material) left little reserve for poor lubrication.
However i changed my valves very early on and ensured the guides got a sploge of lubrication with direct injection between flights.
The Gypsy engines of the time had valves that were 'bathed' in oil due them being downstream in the system.
It is only the top three cylinders that need attention on a PJ so in the 'open' (no cowling) system of a Swift giving them an occaisional squirt is no problem (just like many non aviation engines of the time).
The real benefit comes when you fly behind one,Power,thrust,and that Pobjoy 'growl'. As i soon binned the collector ring exhaust in favour of 'no problem' stubbs the slightly grimy face was a small price to pay.
In non aviation use an early Morgan would be a suitable home for one.
As most of the current engines have the BTH mags fitted it is good practice to open and close the throttle SLOWLY thereby allowing the the mag drive to absorb the input,and giving the piddly little BTH bearing a fighting chance.
Under no circumstances should the 'Gypsy' mag coupling be substituted for the original Pobjoy one, it will not cope with the exta rpm.The original drives may look 'sloppy' but that is the secret of their worth.
Last edited by POBJOY; 16th Dec 2012 at 18:43.