THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

Alfa was similar to Jag. Shim was under bucket but small & capped over the valve stem. Cams out. The only easy OHC on follower engine I know of pre hydraulic lifters was the Alfa Sud boxer engine. Twin cam lobes per follower/bucket. Hole drilled through cam between lobes through which you stuck an Allen key and directly clicked a mechanism in the bucket to adjust lash. All you required other than the Allen key was a fancy Alfa twin pronged tapered feeler gauge. No stripping required other than removing the cam box covers. A very neat design.

I think Fiat did build a 1.6 litre TC engine where the cam ran on the shim pad on top of the bucket/follower. Do not recall the adjustment procedure.
Fiat 125/125S TC ??

John

I cannot remember much about the last FIAT engine I worked on. I do know it was circa 1962 and it was a 1600S Cabriolet twin cam with a fantastic efficient oil filter mounted on the crankshaft nose.

You had to remove the cam chain split link and split the chain to remove the camshafts otherwise the procedure was about the same as a Jaguar XK. Most probably you have much more recent experience as there is some very ingenious tooling out there to cut down the working hours.

I can remember buying a “Craftsman ”tool that you have described, in the USA. On that occasion it was employed replacing springs and seals on an OHV with an F type head.

Better get back on track talking Jaguars or Rob will have us shot at dawn!

Norman, Thanks for your reply which makes sense. Perhaps I was thinking of how Fiat did valve setting on their OHC engines. Anyone know about Fiat engines in this regard?

John

The idea of magnetising any of the valve gear parts would be out of the question for an engine maker. In fact the ones I know use de-magnetisers on major moving parts and certainly all gears to prevent attraction of metal debris.

Given that valve clearances should not need resetting that often, if well-chosen materials are used, the existing system is probably the most economical and easiest.

No doubt the materials may have been improved to retard valve seat recessing, valve stem stretch and valve shim pocketing. That is, if that were possible! Even in 1956 R-R could not obtain EN33 and EN34 material for making camshafts, never mind Jaguar.

If I understand your proposal correctly it involves forming a depression or pocket in the tappet barrel face that is (would be) an expensive part to produce. Trying to machine the bottom of that pocket depression and keeping it parallel to the top face would be a nightmare.

I think the shim would stay in place until the first high speed deceleration when cylinder gas pressure would drop and out would come the shim at high speed……That is if you were lucky. In about 1980 the Rover 2600 model suffered from shim displacement and these shims where in the usual place. The problem, as with your suggestion, is ok until the shim only comes partially out of place and then a forced marriage occurs between Piston and Valve.

Most owners are only interested in valve clearances because of noise but there are a couple of other noise abatement methods available which I will discuss later.

Norman

Thanks everyone, will certainly investigate further, before any action on head removal.

JCS wrote: ↑Mon Nov 30, 2020 9:33 pm
Rob, the tool you saw, do you think it was being used to replace valve stem seals or valve springs by removing the camshafts but without removing the cylinder head?

Possibly Norman it was a long time ago in my hazy memory. It was a clamping tool that I remember, sitting over the bucket with arms either side which depressed the spring and allowed you to take the bucket or shims off the top of the valve without removing the cam. Thinking about the design of the XK now I do not think it was a Jaguar engine so sorry if I miss led anyone. It started a discussion though.

In all my years with exposure to the XK engine I never understood why Jaguar did not design a bucket tappet with a recess on the top that would accept a shim. The he shim would have to be hard enough to not wear as the cam depresses it and magnetic so not to fly out when on the back side of the cam. The advantage is, would be possible to change shims with the cam in place. Is my idea completely unworkable?

The tappet clearances can most certainly be re-shimmed without taking the head off. It is necessary to lift both camshafts. To do that, it is sometimes necessary on the S Types’ to remove the No 1 cylinder camshaft bearing studs on the exhaust side. I think much depends upon the resting place of the engine in its mounts as to whether a foul occurs with the studs at that position.

I am presuming that the garage owner who suggested removing the cylinder head does a nice line in top end gasket sets.

Rob, the tool you saw, do you think it was being used to replace valve stem seals or valve springs by removing the camshafts but without removing the cylinder head?

I have a R-R tool used for valve spring / seal replacement and I reckon it would also do the six cylinder XK Jaguars and Aston Martins.

You might be right Nigel I just remember seeing a video once and they had a tool which depressed the cam follower/valve so when the cam was facing up there was enough room to lift the cam bucket out but that said with my memory it might not have been a Jaguar engine.
At least we are clear though that the "CYLINDER HEAD" does not have to be removed but the cams need to be released and lifted free to get to the buckets. Even the rear buckets on cylinder one are accessible as the back of the engine sits above the bulkhead not under it. The heater box might get in the way a little on the exhaust side but does not block off access to the buckets.

Rob, are you sure about this? The only way to remove the cam followers and shims is to remove the cam. This requires dropping the chain sprockets off the end of the cams then removing the cam bearings. All of them can be done without removing the head. The engine must be first set to TDC with the cams in the correct orientation (slots upper most) checked with cam alignment tool, the engine must not be turned with the cams out as the valves will clash with the pistons and bend them The cams must be refitted ensuring the slots face up again checked with the cam alignment tool.

I stand ready to be corrected on this but I've never come across a Jaguar tool used as described, there is one that depresses the valve once the cam and bucket have been removed but is used too remove the valve when the head is off.