Does anyone know of where I can get a set of Cylinder Head Tappet Retainer Plates for a XK Cylinder Head? I will need 6 of them, 3 for the Inlet Side and 3 for the Exhaust Side. I would prefer the type that uses tapped holes in the head with threaded set screws (Allen Head bolts). Also has anyone here have experience fitting the Retaining Plates to a XK Cylinder Head? I am happy to consider a used set of retaining plates if you have some. Thank you.
Not sure where you are but Limora and SNG usually stock them.
And available from almost every other supplierâŚjust google Jag tappet hold down
SNG Barrett or Welsh. I did not use the cheap screws but opted for socket head. Grease the tap to catch filings.
Pat H
Iâm in the USA, Michigan. Thanks!
I watched a video on iTunes and the guy drilled right through the Cylinder Head into the water jacket, tapped and screwed the Set Screw in with Locktite. Is that OK? Or should you use Thread Locker or just avoid drilling all the way through?
Utube! I hate auto spell check!!
I would avoid drilling into the waterways if you can help it.
The Allen Head Set Screws are 3/4â long (18.0mm), so a 20.0 mm deep hole should suffice?
Wonder why he (on the video) drilled the holes all the way through�??
Not needed in a classic XK, The problems started with XJ6 with all kind of exhaust rules and injection engines, they operate on a much higher temperature. But in classic XK engine with Carburetors do not have problems with tappets going loose.
Unless the head has been worked on and the guides not fitted correctlyâŚSteve
Possibly less the thickness of the plate, but as has been said the early heads do not normally suffer from the loose tappet guides
When I got my XK120 back in 1963 I discovered that it suffered from this problem. Given the other evidence the car exhibited, it had clearly âenjoyedâ a hard existence for itâs first ten years of life. My guess is that at some time it had badly overheated creating the issue. Removing the cylinder head a local machine shop resolved the situation, if memory serves the same way the factory did.
Chris.
Usually the worst that happens is that the guide gets hammered, and you hear it and investigate in time. My XJ is one of the last cars without any emissions things, and I chose not to fit anything; on laters and in general it sure gives peace of mind. Not a big fan of these plates, I would try to fit a grub screw from outside (that may weep oil though).
Most kits come as a set intake and exhaust. I got a set through Terryâs Jaguar Parts, it came from Limora.
few notesâit is a tappet GUIDE hold downâŚ(not the tappetâwhich moves within the guide. The guides are installed cold into a heated cylinder headâŚheld by the contraction of the head when not so hot. The issue, when there is one, is that a cyl head may become overheatedâŚif so more so on the exhaust side, thus expandsâŚmore than the guide doesâŚand the guide loosensâŚ(note that in installation the guide is cool) in operation BOTH guide and cyl head are hot. I have not come upon noted issues with this back in the dayânot in race, nor rallye cars, nor did the Factory mention it, issue a bulletin, issue a hold down kit, nor install hold downs later, nor change the method of factory intallâŚso I venture that issues since are when a cyl head was rebuilt with not optimal heat-cold installationâŚor that over very long period of time, somehow the many hot cold cycles alter the holding of the original installation⌠No harm in adding the hold downsâwhen properly done, and swarf removal is doneâŚI guess then one can worry about the hold down bolts and hold down coming looseâŚbut I havenât heard of that either.
Nick
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Sorry Peter Jan, I canât agree - I found out the hard way that you need them on early XK engines when my '55 XK140 had two tappet guides lift on the inlet side. I had only fitted a set to the exhaust side as perceived wisdom had suggested they were not needed on the inlet cam side. Both guides were badly damaged, with large chunks of the rims being bashed out by the cam hammering them back down. Luckily the debris had not gone into the timing chain gear or anywhere where it could have done damage. The warning noise was not actually particularly loud, sounding more like a wide tappet than anything serious.
I had to remove the head and get it back to the machine shop, who pressed out the damaged tappet guides and heat-shrunk in two new ones. I am sure there was no problem with the original work, but am convinced that as these engines now approach seventy years old it is worth doing everything you can to ensure their continued good health. Itâs a very large aluminium head, with iron tappet guides - aluminium expands more rapidly with heat than iron. For ÂŁ40 a side, I would fit these to any early XK head as insurance. Mine came from SNGB - theyâre easy to fit yourself with a little care, but you shouldnât be drilling anywhere near the waterways. The space the drill goes into is just the oil gallery below the cam in the head, if I remember correctly.
Correct.
Were the guides factory original, any known history etc. that might have led to their failure?
Of course it can still happen but it is much rarer with older engines. Increasing thermostat temperature from ~70 to almost 90 degrees might have something to do with it⌠and higher power output, and I bet tolerances got worse too - the older engines feel better and seem to have had more pride in workmanship 
David, thereâs a whole thread about the problem I had with this, so I donât really want to repeat myself over dimensions of parts etc. The head is the original and had never had machining work prior to my rebuild. Suffice to say I trust completely the firm that do my machining work, who have done countless XK engines since the sixties. The tappet guides were supplied by one of the main suppliers and checked for size. The thermostat fitted is a NOS AC TF1 which I checked in a pan before fitting. The problem surfaced after the first 80-100 miles of driving, with the only possible overheating issue being stationary traffic at road works for maybe 5 minutes or so, when the temp gauge climbed to an indicated 90-95deg. Once the thermostat has opened, it doesnât matter what rating it has - if the engine gets hotter it should stay open. The block and head had a full chemical clean by a large company in Northampton who do nothing else, and the radiator and hoses are all new, with a large electric fan behind the radiator. I donât think there is any way this engine could be made to run cooler. The carâs as close to standard performance-wise as itâs possible to build them, no raise in CR, no âfast roadâ cams (although the most âbasicâ Newman cam has slightly higher lift), the original pair of H6 SUs etc. etc. I donât know why this happened, but the hold down plates are now doing their job OK, and would have been cheap insurance had I done both sides at restoration.