Have been thinking.
I do not know the lube system of the XBR, but I am guessing it has plain big ends and probably some or all plain main bearings, these depend on the oil pressure being maintained for the bearing to float on its layer of oil. (As do all plain bearings?). The oiling to the top end then runs off the 'residual' pressure.
To get more oil to the top end we first need to be happy that the pressure fed to the bottom end is not compromised if we send more to the top end. I do not know how marginal the pump is on the XBR, or if a higher output one can be fitted if the standard one is running close to limit to feed the bottom end.
In running more oil off to the top end we need to ensure that the pressure is not allowed to drop. This probably means a restrictive drilling somewhere - an oil jet fitted into the double banjo?
Is it possible to open up any of the current restrictions over the oil to the top end / exhaust cam. Would putting in a slightly smaller oil jet in the intake cam side and a slightly larger in the oil side cause more oil to pass to the exhaust cam, would this be a problem to the inlet?
If you get more oil to the top end, rather than redistributing it, will there be sufficiant area for it to drain back - does it just run down the cam chain tunnel or are there return lines?
On the oil pump front - if it needs uprating and there is not one that will do the job, would a secondary pump to do the scavenge job and using the standard scavenge to oil the top end? - I am assuming here that the XBR is dry sump.
Just some thoughts
R
