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 much 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. Another thought is that there was some sort of corrosive damage there and someone ground these grooves to remove it... It's very strange. Has anyone ever seen this or heard of cam followers on early cars suffering from any sort of serious corrosion issues? Or physical cracking? BTW Those 2 followers fit perfectly in to the buckets and there is no sign of anything happening that could have caused this much damage.

Thanks

 

Looks like a lot of surface corrosion on the insides of those buckets, my theory would be that at some point the valves were sticking as there has not been much oil around that valvetrain dry start after long period of idle and possibly threw the collets, 2 collets and 2 chunks missing ? Was that why work was carried out ? Is there any evidence of any other witness marks anywhere.

I can't imagine that corrosive exhaust gases would cause such localised damage/wear to the buckets, looks more like mechanical damage than has been fettled to remove burrs and refitted rather than replaced. Again only my theory, not seen that sort of damage to the buckets before.

 

Thanks @TilleyJon

I don't know when or why they had the the head off (other than it must've been before the late 80's when my friend got it) but I found that on the intake side 5 out of 6 of the shims were from another brand of car and were smaller diameter and marked metrically. One of them was even smaller than Jags 'A' size shim. Also some rudimentary marks on the front cam bearing caps showing where the camshaft alignment slot should go. Also some ham-fisted turning of the upper timing chain adjuster wheel damaging the holes considerably. So head was definitely off.

Thrown collets and grinding out the damage is a good theory... The thing I find so odd - other than the marks themselves - is the extra blackness on those 2 valve assemblies. I suppose possibly the valve guides were damaged and they are leaking more exhaust than the others...

 

What thickness were the smaller shims ? Standard shims are 85 - 110 thou so would be interesting to know what the ones fitted are, generally the reason some are off size is for out of standard thickness requirements.

Check the valve guides to see if they are oval, this is the most common wear on these valve guides, with what you are seeing I would want to pull the head to see what the hell has happened to that head, I know the car sits a lot but long term I would like to know what state the engine is in if someone has done that sort of thing.

You could do a leak down test to give you a much better analysis of the condition before pulling the head, it will give you an idea what the valve seats, pistons etc. are like

 

Shims on the intake side were in range but near the small end of the spectrum - an A and a couple B's etc... except for the tight one that needs .081" - I think the slackers who did the valves just didn't want buy the Jag shims and used whatever thy had around which were some kind of metric shim. The exhaust side stems were ground so that they are in a more normal range - Q, O, R etc... Not sure why they ground one side and not the other.

If this was my car I'd pull the head but the owner doesn't want to cause he's happy with how it runs. It had to have been like this for a looong time and although it sits alot he has driven it thousands of miles in the 30 years he's had it.

I did a normal wet and dry compression test before pulling the cams as a matter of course. All were okay and very close in pressure. I definitely agree with doing a leak down test but I doubt the owner would pull the engine regardless of what it showed - He just wants it to stop leaking from the cam covers. It irks me since I'd give anything if my Mk2 was as pretty as his

Thanks!

 

Unfortunately you are a little limited if the owner only wants to deal with the one issue, guess you will never really know what went on.

Looks like they have over cut the valve seats if they have ground the stems, but without popping the head you won't know for sure, just guesswork.

Hopefully he has many more miles of happy motoring with the car and you can buy it off him in the future Mike.