Oil pressure at idle is around 20psi, and 40 - 45 at 2000 RPM - this is according to the in-dash gauge. The knock is easy to hear upon startup (like the video) but after the car has been running and gets to around 60 degrees C or 140 F (again, by the gauge) the knock is there, but would be easy to miss if you were not listening for it.

 

That's fine. Seems the bottom end of the engine & oil pump is healthy. I find myself having to re calibrate with these old cast iron block, very long piston skirt, long stroke engines. Piston slap in the modern aluminium block, Alusil bore, ultra short piston skirt engine sounds quite different. (it's a hollow tapping sound)

A bearing knock (crank or small end) will not reduce as the engine warms up. It will tend to increase.

 

Well, I'm certainly hoping that it is a condition I can live with for a while. The prospect of a rebuild is itself a tad unpleasant, but I'd feel better about it if the engine was also otherwise a ruin of worn parts, sludge-filled oil passages and asthmatic compression - but as it is, I'm continually surprised at the engine's condition. I've never looked at an unknown mileage engine, presumed to be in excess of 100K, and found it so clean. The oil is golden, I can find no hint of sludge, or build-up on any internal parts I've so far examined, the breather tube was clean and free of any oil, compression figures were enviable for an engine in any condition and best as I can tell, it doesn't even leak any oil - nada - nothing - nothing on the ground, nothing from the rear seal (best as I can tell). The only issues I can find are piston slap that diminishes with temperature and a curious volume of white smoke that although lacking all other indicators, makes me suspect a head gasket. I'd really hate to have the engine torn down if its only real problem is an annoying knock that goes away after 5 minutes.

 

I would highly recommend a leak down test to identify the slapping cylinder, then put a boroscope down the spark plug hole to see what scoring there is in the bore.

The piston slap will only get worse and there is a possibility of breaking the piston skirt, if this ends up in the crank (which it will if it breaks off) you can guess the possibilities !

I personally would not continue driving a car with piston slap as this will almost certainly end up with a higher rebuild cost and a possibility of a wrecked crank and other damage should the piston drop part of the skirt in the crank.

Obviously this is my personal opinion and you may get away with it for quite a long time, but I would make sure that there is no bore damage already happening before continuing to drive it at the very least.

 

I would also check that the cam follower sleeves haven't come loose in the block and also check the valve clearances and that the shims are the correct size (width not just depth as I've seen thicker shims from other cars used in the past when the standard jaguar shims weren't enough).

 

Piston slap seems to be one of these issues that has a consensus on how annoying it is, but no such agreement on how damaging it is - with reports of successful mileage 50K+, to dire implications if the engine is so much as started, being equally plentiful. As it stands today, the car is not a driver, but I'd like it to be fairly soon. I have a local mechanic who claims to be an XK expert - he has rebuilt several, and one was a seized motor from an XKE, and he has that one purring like an angry kitten - So I'll get his take on appropriate next steps.

The issue I have with a leak down test, is that the compression test provided no evidence of a problem, if anything it suggested a very healthy engine. My general understanding is that a compression test will indicate that there is a problem, whereas a leak down test will tell you what the problem is. In my case however, the compression test did not indicate leaks or issues at all, so if there is no "leaking" occurring, I'm not sure if a leak down test will prove valuable.


Yes - agreed - if the motor goes in for any sort of work, I'll have them do all the reasonable checks and adjustments while they have it opened up.

 

Obviously this is all my own opinion and best advice I can give you with the information you have given.