Lubrication of cam followers

[Napolean (Michael Wilding)]

Hi Guys
I was cleaning up the blocks that hold the cam followers and noticed that the centre block does not have lubrication holes for the follower stems. There is an oil gallery just as for the 2 other blocks which are lubricated. At first I thought my centre block was faulty but on inspection of another found it to be exactly the same. This means that the centre 4 followers are operating on very limited lubrication.Do you think it would be worthwhile using a small carbide drill to add holes as per the other 2 blocks?

[Roger_McWilliams]

Oil from each rocker flows down the outside of each corresponding push rod to lubricate each valve tappet and the camshaft surface in contact with each tappet.

[Napolean (Michael Wilding)]

Immediately behind the centre block is an oil gallery - so 4 small holes would force feed lubrication to the follower stems like in the other 2 blocks. Seems a better lubrication method to me rather than relying on oil dripping off a dynamic push rod.

[Peter_Scott]

I wonder if the decision not to feed the tappets at this point was because they were more concerned by loosing oil pressure to the centre main. I can’t say that I’ve noticed any particular problem with wear on the centre four tappets but the centre main bearing is really vulnerable.

Peter

[Ed_Nantes]

Yes , the oil doesn’t just 'drip’óff. If all is done correctly quite an amount of oil runs down each push rod The wear factor on cam followers is the surface that the cam lobe runs on , not the stems.

[Rob_Reilly]

We discussed those tappet blocks once before, in connection with the holding screw lengths.

2.5 litre engine anomalies

Hi All, As a relatively new member of this much valued forum, this is my very first post. I am on a very steep learing curve and I would very much appreciate any help and advice. Shortly after buying a 1948 MkIV 2.5 saloon (barn find) I discovered the Jag-lovers forum and have become a frequent reader of the interesting articles in the Pre-XK section. I eventually made a start on the project early this year and decided to first strip and rebuild the engine that hadnt run since 1975. I was v…

I have two sets from Mark Vs and none of them have any holes through to the stems.

and there are no supply holes in the block.

[Napolean (Michael Wilding)]

Thanks for the input guys. If all the holes have been deleted in the Mk5, then Jaguar must have deemed them unnecessary. Will bolt it back together and leave it as standard.

[Ed_Nantes]

@Napolean

Will bolt it back together and leave it as standard.

Now that you mention 'standard"I wonder… the holes would have been needed on the sidevave SS1 engines as there were no pushrods or over head ear to supply oil
As the OHV engines started out as a conversion, One might think the holes were just an historic carry over,like a persons appendix.
Until someone though , we do’t need these and can save tuppence halfpenny per engine by omitting that step.

[twojagsjohn (John Mellor)]

When I was overhauling my 2.5 engine earlier this year I came to the same conclusion and decided to seal the feed holes in the block with brass plugs,in order to eliminate any internal oil leaks / pressure loss (albeit relatively minor) from between the tappet blocks and crankcase.
I suspect the side valve versions may have had a gasket fitted here previously.