Square four timing side main bush

[Brian.Challinor]

After splitting the crankcases, I noticed that the oil holes in the plain bushes are in the 5 past 7 position. Should they be Horizontal? I think I' ve read that they should be horizontal, but surely with the groove in the bush on the outer edge it won't make a difference. I don't know why the engine top end was stripped so I am starting from scratch. I was surprised to find no wear in the mains or the big ends but I not to sure about the holes in the plain bushes.

[nevhunter]

As part of an engineering course I did at The University of Technology,( NSW) years ago, The location of lube feed holes was covered in detail and Ariel twins and fours were dealt with specifically.
Where oil is fed to a bearing is often absolutely critical. When a shaft rotates in a bearing the oil builds up local high pressure areas as part of carrying the load. If you tried to feed the oil into the bearing at those places, no reasonable amount of pressure would get any in. In fact oil will exit the bearing from a hole in the wrong place. At the opposite point there is no real pressure and you could lubricate it with an oil can (almost)
An oil hole or groove in the wrong place in a bearing will reduce the oil films ability to do the job. I don't put spiral grooves in bearings that are loaded from one side anymore, (unless they are there to let grease through on a cement mixer or such. Nev

[david.anderson]

Brian
the oil supply to the timing side bushes is through two horizontal holes in the crankcase either side of each timing side mains . With the oilway groove around the outside of the bush (as opposed to the inner bearng surface) it doesnt matter if the bush is not installed with the oil holes directly opposite the oilways in the crankcase (or if the bush spins a little in the case). Most square 4s that I have checked have not had the oil holes aligned. As Nev said though there should not be any grooves in the actual bearing surface of the bush. regards David.

[Brian.Challinor]

David
My bushes are in very good condition, thanks for putting me right about the holes.