I have a 2001 xkr that i am planning on replacing the chain tensioners on, it has quite high mileage, do i just need to replace the upper tensioners, the chains look good and tight with no stretched areas.

 

Most replace only the upper tensioners but there have been lower failures also. Chains do not appear to be a problem unless affected by the tensioner issues. Some have changed them, most have not. The answer to your question is based on what do you mean by 'higher mileage' and what are your plans for the car over the next several years.

. . . and welcome to the forum!

 

If you have high mileage I would be more worried about the guides, they become brittle and crack, worse case scenario all you end up with is a metal strip as all the plastic has broken away

 

I had an upper tensioner fail, it broke the secondary chain, so I decided while I was in there to replace all tensioners and chains. The chains might have been overkill, but all of the tensioners and guides were cracked and looked like they could fail anytime. I had right at 90k on my XK8 when it failed. Phil

 

Higher mileage means 190k, all highway mileage though. I think that I will replace all of the tensioners and guides, I want to keep the car for a couple years, so I think the peace of mind will be worth it.

Incidentally, while I am asking questions, can you get the valve covers off a supercharged engine without removing the intercoolers?

 

At 190K, I agree, do it all.

You do not need to remove the intercoolers.

 

@XKracer,

On your posted photo, there is nothing missing.
that little notch is supposed to be there.

But looking at the crack, a change out is the only option anyway

 

It was the crack I was referring to, I have worse pics!!

This pic shows what happens when the guides fail, the timing chain acts like a chain saw and starts working its way through the heads!!




As a side note the previous pic was from an XK that had done only 50K miles imagine how bad it might be after 150K

 

Well, under closer inspection, it looks as though the engine has dropped 3 valve seats, (it was bought as a non runner). I have a lead on a used engine that is already out of the car, but has a bottom end noise, could this be anything other than bottom end bearings, and do the ford engine parts cross over to the supercharged engine parts? I will still need to do the tensioners on the new engine I am sure.

 

I do not know if other ford orientated engnines share the same internals, but I can tell you it is not a ford engine, all ford supplied was a sump plug the rest was completely Jaguar made.
The engine consists of 'sandwich plates' to hold everything together, if the bottom end is noisy you would be looking at new crank and bearings, nobody as of yet are doing regrind options for these cranks (AFAIK), they do wear very well.
If I was you I would look for a better engine or make sure you get a really good deal on the way you have found, of course you could get your heads sorted, might be a good time to have some fun.

I know where there are a couple of low mileage heads

 

My new 2001 XK8 has 37K. Should I be worried about the tensioners at this stage or is this something to look at when I get it up in the 80s?

 

Don't wait, time will also make the plastic brittle, I just changed a set on a 2001MY with 36K on the clock and they were just showing signs of splitting.

It is not worth taking the risk

 

If you have plastic second generation tensioners, you should have them replaced with the later generation metal-type tensioners...soon. The consequences (and related expense) when the plastic ones come apart are just too great to gamble with.

 

If you have the plastic tensioners, even with low miles, you should take care of this soon as preventative maintenance. With a 2001, you probaly have the plastic tensioners.

 

ALL '01 engines and some percentage of '02 engines were built with the plastic tensioners. My 'June '01 assembled '02 model year had plastic.

August 13, 2001 was the conversion date.

 

Okay, so does someone know a guy in the Dallas Fort Worth area that can do this and what would it cost?