Hi all, just cleaning up my con rods for the 3.4 and see that there is a hole on the top of the con rod which is blanked off by the bearing, did early engines have a hole in the bearing to spray oil to the underside of the piston?
hi robin - i do not think this was done on any xk engine. oil spray on piston required better oils not available widely until 1970s.
Robin
The hole in your con rod is to lubricate the small end bearing. Either the small end bush has turned in the eye of the rod and is therefore blanking off the oil feed, or someone has fitted new small end bushes and not drilled the bushes. If you look inside the rod end you should be able to determine if the bush has turned, in which case it is imperative that the bush be replaced.
Oil spray onto the underside of the piston would in any case be taken from a separate jet or by a drilling in the rod near the top. It is doubtful if any oil that has flowed around the small end would have enough residue pressure to reach the underside of the piston.
The bushes are all orientated correctly with the oil hole lined up with the drilling from the big end, that was one of the first things I checked but thanks anyway.
The hole I am talking about is on the crown of the little end, thinking about it it may just be a tooling hole to meet the big end drilling, means Jaguar could use a shorter drill, there you go 
Robin
When these bushes are supplied they have one hole which has to be lined up with the rod oil supply when they are fitted, the situation you now are experiencing , After fitting they are drilled again through the top end hole to provide further lubrication. In your case the top holes have not been drilled after the bushes were fitted.
Not too sure about that, these are the original bushes, I can’t see a manufacturer introducing a further step in the process when it would be easier to drill the bush during the manufacturing process.
I’m a retired toolmaker and used to work in engineering/manufacturing environments.
Robin
As you say the rods are drilled and unless they changed the lubrication during production I would be fairly sure the bushes would be drilled. Many manufacturers carried out extra drilling to suit all sorts of circumstances and it does not make sense not to drill the bushes. It is possible that they decided not to drill the tops, but only this week I pulled rods from a 1965 3.4 S type and the tops were drilled.
Not drilling would have save them an operation and they could have decided they did not need that extra lubrication as R-R found out with their post war 6 and 8 cylinders. They conducted tests to eliminate the top end oil supply whilst still leaving the rod drillings and found no increase in wear…
I’m a semi retired auto engineer used to working in production plants and on top end cars in 56 countries and can only relate that experience.