Would you expect used shims to be reinstalled in a professionally reconditioned XK engine? And I mean with signs of wear on the shims.
Advise please.
Always have, and is typical reuse in all engine shops overhauling an XK engine. If valve stem wear is apparent, turn them upside down, so smooth side now on valve stem.
If your collection of used shims is missing sizes you need, surface grind thicker ones down to size, and in doing so remove side with valve stem were, but proper machinery, impossible to accurately grind by hand/eye.
If you are still short, then find more used ones, or as last resort buy a few new ones.
No issues at all reusing old shims in good condition, so long as not thinner than minimum limit - .085 I think.
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Hi Roger.
Thanks for the reply.
Yes I can fully understand reusing shims by having them linished or turned over so a fresh flat face is present on the top of the valve stem.
Now. How about used shims being reinstalled with a worn face on the valve stem.
Would that be typical when overhauling a XK engine?
This is what I’ve just found on investigating excessive valve train noise in my rebuilt XK engine.
Regards.
No, I certainly wouldn’t personally refit worn shims with worn depression bearing on valve stem, as I would think that could potentially introduce some in service variability to clearance, but I doubt it would cause excessive valve train noise, with the operative word on excessive. But wider clearances give greater noise, thus the original .006 and .008 XK120 Valve Clearances being reduced to .004 and .006 for Mark VII engines, as it was deemed a Mark VII owner would be less accepting of valve train noise than an XK120 owner.
But I always worked on that I would rather be able to hear each valve-tappet, than not hear them, as if any valve closes up, you risk a burnt valve.
Good luck with your investigation – can be hard to find source of certain noises, and indeed when there are quantitative considerations as to what is excessive or not.
Not a good practice: have you discussed this with the rebuilder?
I would never expect to see this. I sure wouldn’t do it. It’s too hard to accurately measure. It might not have been worn evenly. The edge of the dimple might be catching on the stem. I’ll flip just once and when that goes out of spec, toss it. I’ve sanded a couple in an absolute pinch but it’s honestly not worth the hand cramps to save 5 bucks. Plus then there is the question of whether by cutting them it’s cutting through a hardened layer so it will just fail faster.
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I didn’t regrind worn shims even when I had access to a mag bed horizontal grinder and free highly skilled labor.
Many, MANY moons ago, Dad got a PILE of really thick shims, and the machine shop we used let him surface grind his own.
At the time, our shop would have 4-6 Jaguars, at any given time in the process of rebuilding.
Dad put me to work, setting valves.
There’s bound to be someone else that uses the same shims? Are these things unique to Jaguar? I’m looking at your Datsun timing chain tensioner comments and wondering why I didn’t know that.
Alfas and Astons used little “top hats,” that fit on the valve stems, and the Rover uses two pads, per valve, a thick and a thin one, but smaller diameter.
Have discussed it. It is their standard practice to reuse shims but as I mentioned to them this would be in the form of turning them over to a flat face and not reinstalling the worn side to the valve.
Perhaps you’re asking because usual vendors are closed… but I recall the cost of new shims was reasonable, plus when I ordered the ones I thought I needed Armando at XKs assured me he could pop a few in an envelope to me if I needed couple other sizes to dial it in. Hopefully that level of service is still available under the new owners.
Here are the measurements found on my engine.
Note this engine has not yet covered 200 miles since rebuild.
Factory specs are Inlet .004". Exhaust .006"
The excessive noise was noted as being from the inlet side at the front which is where the largest clearances were recorded. No other issues were found so am hoping for a quieter engine when it is returned to factory clearance specs.
Inlet side. (.004") Exhaust side. (.006")
No.1 .006" .004"
2 .007" .005"
3 .005" .006"
4 .005" .004"
5 .005" .006"
6 .005" .004"
You definitely do not want the exhausts under 6: that said, I always set valves at 6 (int) and 8 (exh), and the increase in noise was not noticeable, and that afforded increased service intervals.
Thanks Wiggles.
My measurements seem to be all over the place. I will be setting mine to factory specs of .004 and .006 in the hope that it reduces the noise. I have no issue hearing the valve train from the drivers seat but there was a particularly increased tapping noise, above that of what would be expected, that was annoying.
That’s pretty typical bedding-in, on a new engine, thus the requirement to check, and if necessary to redo clearances after running-in period, I usually allow a 1000 miles.
But as before, .006 and .008 were the original recommended clearances for XK120 engines, but when Mark VII was introduced factory reduced recommendation to .004 and .006 purely to reduce noise levels that are amplified through the polished aluminium cam covers, but after a period of no adverse side effects, Jaguar then standardised on .004 and .006 for XK120 as well, more as a result of the FHC being more prone to customers concerned about tappet noise than were Open Car owners.
Have to say, whenever I do engines I stay with .006 and .008 as the noise doesn’t worry me, but the risk of clearances closing up to minus or zero will burn valves, and that’s a head off job, and start again.
But after 1000 miles, everything likely to bed-in, will have mostly, so you should be safe resetting at .004 and .006, but do check again after more miles - depends how you drive car.
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I’m looking for details of the cam bearing caps. They seem to be missing from the parts book? Do they have dowel pins or only dowel rings for the studs?
Just the dowel rings around the studs.
Not at all. The engineer in me is curious to know if these same parts are used by other manufacturers. You see a lot of stuff show up in unexpected places. Until I inadvertently bought one, I had no idea you could swap the distributor out of a Ferrari 250 GT V12 into a Jaguar XK 6 cylinder. Jaguar was not unique in the British auto industry for using large numbers of bought-out parts.
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Not sure i grok how THAT works…?
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