so , today , i sat down with some feeler gauges, some paper and a pen ( Jaguar pen at that
), i had previously noted all the shim sizes under the lifter buckets under the cam shafts , the shim size was still readable on the shim surface , this was denoted as a '30 or a '26 etc, for all 24 valves , my original shims ranged from #27 to #38 across the 24 valves
then with the feeler gauges i measured the gap between the back lobe and the follower top for each valve, this should be between 0.012" to 0.014" of an inch for inlet and exhaust , ( 12 to 14 thou )
noting each reading under the original shim size for each valve , as can be expected, with some wear and also the lapping of the valves, not many were within tolerance, but most were very close , some 0.0015" and a little more on some (measured at 0.0155" for example + 1.5 thou over max tollerance of 14 thou )
still with me ??
so , now with the original shim size and the new reading of gap , and some calculations i could work out how much bigger a new shim would need to be to close the gap to within tolerance ( 12 to 14 thou ) X24 , lol
so , looking at the parts on Jaguar Heritage, i could work out which new shim i needed , but hold on , not quite that simple, for example a #29 shim is measured at 0.0985" , i need a shim 1.5 thou thicker , so 0.1000" is needed, so looking through the shim table to find the new size, it turns out i now need a #33 reference size shim ,
fun isn't it , lol
so , with some swapping undersize for over size and making a list, i needed x7 new shims of the calculated size , and they should be in tomorrow , cost £4.02 each including VAT , so im happy with that to be honest ,
wish me luck
btw, gap tolerance is between 12 and 14 thou , however it is recommended to go towards the 14 thou side as a little noise is much more preferable to tight tolerances once the engine is at running temperature causing potential galling of metal surfaces....