Hi,
I’m helping a friend with Mk2 that he is working on and I came across something I’ve never seen on any of the many XK engine powered Jags I’ve owned over the years.
Car is a 1960 3.8 that he’s owned since the 80’s. Has about 75K miles that he says is original. It runs fairly well although it does do alot of sitting. Compression test is good and all the cylinders are very close to each other. He pulled the cam covers to change the gaskets and while in there we did the cam-follower clearances. I can tell the head was definitely worked on at some time prior to his ownership.
After pulling the cams I popped out the cam followers and I found something strange on 2 on the exhaust side – #1 and #3 both have these strange grooves/chunks missing in the bottom of the skirt (see pics). I also noticed that on those 2 valve assemblies there was more black gunk than on the others.
The grooves look more like corrosion than wear and with that and the extra black gunk on the springs, valve stems and retainers make me theorize that those 2 valve guides are worn more than the others allowing blow-by exhaust to get past the guides and condense onto the follower skirts, the corrosive elements in the exhaust doing their work on them. Just a theory of course - I am wondering if anyone has ever seen this before - I have never heard of this kind of wear. It was hard to get great pics with the flash but the areas of the grooves have pits in them like corrosion.
Thanks,
~Mike
I would be more concerned with the missing pieces of the skirt?
Definitely wonder where the pieces went but this doesn’t look new - it coulda been like this since before whoever rebuilt the head in the 80’s - they could’ve even put it back together like this. My biggest concern is that I can’t see anything that would have caused this. The followers sit in the buckets just like all the others - don’t feel strange or tight… it’s mysterious.
If the damaged happened with the tappet in place , I would have thought the parts would still be there !
They look like grinder nicks to me .
As you say the head has been worked on , maybe there was some damage , or even cracks some one ground out !
They certainly look like grinder nicks, chamfered and all. (Balanced tappets surely, because why not?). The wear in general; a bit much but I think the pattern makes sense. The tappets rotate in use and so the wear pattern is even, but maybe they have a bit too much play? The corrosion matches that of the inside and didn’t get rubbed off by running.
Hi @residentalien and @davidsxj6 - They do look similar to grinder marks but a few things make me think that they aren’t. One is that there is sort of pitted corrosion in them that’s hard to see in the pics. Second is that some of them are thin in the inside of the follower near the groove. This is also a little hard to see in the pics. The third thing and possibly the most telling is that both of those valve assemblies are much blacker than any of the others - like more exhaust gas is leaking past the guide on those 2.
I’ve personally never heard of cam followers cracking (has anyone else?) but I suppose it’s possible someone did grind them many years ago to relieve a crack. I thought that I read somewhere that the metallic composition of cam followers in XK engines were changed at some point… Possibly early versions were more ferrous and prone to corrosion?
I don’t know… it’s really odd. As I said before they fit into the buckets perfectly and there are no other outward signs of something broken or anything outside of normal wear going on. I guess the mystery continues.
