Hi Everyone - I'm new to this particular site but not to Jags,

Over the past weekend I installed a stake-down kit on the exhaust
side of the head. After coating liberally with assembly lube and
buttoning everything up I cranked it over and watched through the
oil filler hole. It took a heck of a long time for oil to get to the
point where I could see it through the hole - creeping over from
the rear of the camshaft. Couldn't see anything oozing out of the
visible front bearings.

I also noticed while I had the cam out that the cam bearings got
successively more worn-looking toward #6. I know that the oil is
delivered through the split tube at the back of the heads and into
the back of the camshaft - through the middle to each bearing.
Stupidly I didn't blow out the oil gallery in the camshaft before
re-installing.

The engine has adequate (well within spec) oil pressure at all
times but I get the impression from the sound coming from the
exhaust side of the valve train that oil is not flowing well in
that area. Cam follower clearances are spot-on perfect (.012
or .013 everywhere) so it's definitely not that. It's not superloud
but it's definitely louder than the intake side. Ever since I
adjusted the clearances a few months back I thought the remaining
sound was because it needed a stake-down kit to quiet a possibly-
loosening tappet bucket but after install no difference in the
sound.

So with that and the evidence of how long it took for oil to wind
up at the front of the cam and the look of the bearings I am fairly
confident that oil is not getting where it's supposed to go very
well.

The car needs an oil change 'cause oil is a little old (very few
miles on it though). This weekend I'm gonna drain it cold, refill
with 5w20 and run it to operating temp then drain again, change the
filter and refill with the correct 20w50 in hopes of 'flushing' it
out. I'm leary of using any kind of oil-flush product 'cause I've never had much confidence in magic-bullet style fixes.

I also intend to remove the oil feed tube and make sure it's clear. Is there any precedence for a clog in the tube? Any other thoughts?

Thanks - Mike
73 Series 1 XJ6 in New Jersey

 

Well..........

The engines in these cars are no longer youngsters so various things can gradually build up and conspire to affect how the engine works.

Clearly a DOHC engine needs a generous oil supply to the head so it can continue working reliably; there are those cam bearings for a start, and the cams themselves to keep lubed. In addition, the overflow from the head is used to lube the camchains and sprockets. If you ever get the chance to see inside the camchain chest, take a look at the ingenious little oil collector for the jockey sprocket, (the one used to adjust the top chain).

Aware of the need for generous lubing, Jaguar provided a pretty good oil supply to the head, the supply being taken off the feed to the rear main bearing opposite to the main oil gallery, so should be at main gallery pressure or near to. However when it came to lubing the head components themselves, over the years from 1948 to 1986, Jaguar had a somewhat schizophrenic attitude when it came to the cams. Some cams had an oil supply to each cam via a hole from the cam gallery to the base circle of the cam. After a while, this was dropped, as it had a bad effect on pressure to the cam bearings. Then, oddly, it came back for a bit, then was finally eliminated, so eventually the cams were only splash lubed giving the oil pressure fully to the cam bearings.

Clearly, after decades of use, the oil passages up to the head, (and those inside the block as well !!), are going to get blocked to a certain extent, so it would be wise to ensure the pipe to the head is clean and free of crud, and also the camshaft oil galleries. I would think the best cleaning tool is a shotgun barrel brush, (a 410 comes to mind), plus plenty of kerosene or maybe cellulose thinners, followed by an airline.

So.........

1. remove oil feed pipe and rigorously clean it out.
2. remove camshafts and clean the oil galleries as suggested.

 

Thanks Fraser - we're thinking along the same lines. Definitely gonna remove and be sure that line is clear. If I'm feeling industrious on the weekend I may remove the cam again and really clean out the passages then flush the engine with cheaper 5w20 oil as described in my first post.

 

BTW how many miles on the engine ?

 

On the newer engines exhibiting varnish, a couple of the most respected techs here recommend flushing by adding a quart of Dexron to the old oil, bringing to hot idle and draining.

 

There odometer says around 80k and I think it's correct. Doesn't burn any oil and compression is even although probably a little low... but it is a Federal low compression engine.

 

I've heard that one before applied to loosening stuck lifters in a pushrod engine and it crossed my mind but now that you mention it and say that it is a recommended method on Jags I think I will try it. Thanks!

 

Today I removed the oil feed tubing. Didn't see any obvious blockage but I did blow it out and cleaned it thoroughly before re-installing. Also used the quart-of-dexron flush method, ran it to operating temp for a while then drained, changed oil and filter.

It has quieted down now to the point that I don't think it could get any better. All I hear is the rhythmic sound of the cams working against the cam-followers. So problem solved!

Thanks!