BIG QUESTION I have is whether performing modifications on a 12 year old coupe with 94,5000 miles is a bad idea.
Two areas of consideration:

1. Handling improvements: larger rear anti-roll bar and lower frame braces front and back from Ultra Racing ($750 in parts alone), and lowering springs (if someone can attest they really help handling vs are just an appearance preference).

2. Supercharger upgrade via lower pulley from a vendor that maintains "harmonic balance" function that AVOS has warned is deliberately dismissed by at least one vendor.

 

I have a 2002 XKR (only 55k miles) that I have modified (LSD, 3.27 rear axle ratio, lower s/c pulley, s/c inlet/outlet ports bored out) and I'm very happy with the results.


Mark

 

It's up to you how much it's worth spending on your car, but don't let age or mileage deter you. Plenty of guys on this forum have multiple upgrades done to cars older than yours.

To get an idea of how well it can go, read thru this thread: https://www.jaguarforums.com/forum/x...kit-usa-82598/

The suspension upgrades are a no-brainer. The engine mods are different, but these are pretty solid cars.

 

I do not have any metrics about lowered handling vs. std. ride ht. but the laws of physics apply as a lowered center of gravity is preferred in most instances. Additionally most, if not all, lowering springs are progressive so the ride quality is not diminished but stiffens when pushed. My seat of the pants metrics tells me it handles better. Also do not over look the tires, they may be the single most important element of your handling upgrade.

 

 

It's not a bad idea if you want to do it... and you have been asking WAY too many questions for anyone to believe you don't want to do it.

I put a twin screw on a 10yr old car with 70k miles. It is now within a stones throw of 80k miles and I couldn't be happier.

+1 on what Marc said about tires, if you are running 18s with soft sidewall tires, you can get a lot of benefit from different tires or changing wheels to a larger diameter.

1) I'm interested in your experience here as I'm looking to do something similar.

 

If your plan is to go insane you'd be better off swapping for a newer car say a 2004-06 XKR. Even if you were to drive your existing car off a cliff and not resell it the improvements will cut the overall price of your project significantly. I started with a 1999 XK8 and swapped for a 2004 XKR and estimate I saved a ton by doing that. If not tons of folks upgrade older cars just fine and my old XK8 was rather nice in the hills with minor mods (wheels etc.).

 

Weisberg,
I think a lot depends upon how long you intend to keep the car. If the answer is forever or close to it, why not? I have 135K miles on my 2002 XKR, and although it has had its share of maintenance over the past year or so, it runs as well as it has at any time since I bought the car with about 60K on it.

So, if you're really wondering whether or not the car is up to going another 95K miles, so that you can enjoy those upgrades, I would say, "Go for it!" The car will take it If, however, you're thinking of selling in the near future (as I believe you previously were thinking about), you'll not recover the expense of the upgrades in resale. The reality is that as beautiful, classic, and well performing as they are, a 100K mile XKR is just not going to bring you much over $10-13,000, not very much compared to the cost of new cars. But very few new cars will give you as much enjoyment, luxury, and attention as yours.

Good luck with your decision.
Ted

 

Thanks to all of you. I am familiar with nearly all of your car stories but was not sure if I had joined the party too late to amp it up for mine.

I put my car up for sale for a month and decided against it when I realized what I would get for it versus the costs and benefits of cars 5 years newer. Factoring in the low cost of insurance, and doing modifications looked very attractive as long as I wasn’t doing anything to greatly diminish the life of the car.

CC fulton: YES I have been asking a lot of questions, there IS a reason :-)

Marsden: thanks for the information on other cars you had perspective on, you can see I decided to stay jag xk100

tberg: I did not realize how many miles you’ve put on yours but that helps, especially in view of your Panterra and weekends of racing in an Audi S5

mjlaris: your modifications cover everything before crazy $ level

enderle: I cannot afford to go "insane" like you, ccfulton or Jeff in Tucson but all of your modification stories have been great vicarious experiences.

 

I guess you could say as far as modifications go, I can probably give the best aspect from my customer base....... I have mild "modders", I have some lunatics, but I also have "Mad Bob", he is the nicest to guy to meet, just has some crazy ideas as far as body to powers enhancements go

The point is ...... The range of cars go from the very earliest to the very last, mileage also from the lowest (2004 XKR with only 21k) to the highest (1996 XK8 180k). I do not believe there is a cut off point, no matter how old or new. If there was ever one factor, it would be condition, IMO it is pointless modifying a dog, something that requires a helluva lot more than bolting on a few goodies, rattling engines and badly corroded bodies just cause the bill to escalate...... You need to do your mods on the "best" XK you can afford.... After that, fill your boots

 

Another key point for all is the importance of a proper 4 wheel alignment. It seems obvious but if the car isn't set up right all the mods in the world won't help and proper alignment of the X100's rear is more important than you'd think.

Charlie:

I know this is unsolicited but for more insight on this topic you may want to talk to Gregory @ British Auto, he knows my car well and can tell you about the handling, he once stated he preferred my XKR to an AM Vantage V8. In 2007 my car was the first car he installed Powerflex bushings into, I sourced them from the U.K. back then. He now keeps a stock of them at his shop.

 

My car had extensive maintenance throughout 2012 by the previous owner and then me. New CATS shocks in the front plus nearly every bushing except the lower control arms, which I then had done (that made a big difference) along with new brakes, new Michelin Pilot Sport A/S tires and 4 wheel alignment, 3rd brake light, coolant reservoir, 2 oil changes, transmission fluid change and then another 4 wheel alignment because I wanted to double check the prior guy's work 12 months earlier... Then I did the rear muffler delete. It's in good shape now, rattle free.

So this is about modifying a solid, well maintained coupe.

XK Racer, thanks for contributing.

 

+1 from me

 

Ok, so how about my first step be the larger 20mm rear anti-roll bar from UltraRacing along with PowerFlex bushings on that anti-roll bar?

Anything else that begs to be done at that time so as not to have duplicative labor by my mechanic?

Is the rear frame brace by UltraRacing important to do then or can it wait?

Lowering springs? If so, whose? Mina springs are half the price of Arden and I get the impression the labor cost for any springs is going to run $1,000. Is that correct?

LSD and rear axle ratio change look too expensive for me to do so that's out of consideration.

I won't bother with power upgrades until the handling is better. I figure after handling the blue top transmission solinoids would be next.

 

The sway bar is more or less independent of the other things, so if you want to see the incremental benefit of each new part, you could probably do them one at a time. Or you could go for broke.

Probably should replace the sway bar end links at the same time and since you are ordering from powerflex, might as well get the end link bushes too. The Jaguar parts are a silly price, but Rock Auto and some other sites carry end links from other manufacturers.

 

If you go with all poly bushings you get the end link bushings in the kit.

 

Any scraping issues with the lower frame braces?

 

If you're starting off with an XK8 versus an XKR, you might want to consider an engine swap to an LS-6 or similar Chevy motor. Others have done that and it's a great upgrade - was thinking of doing that to my XK8 before it got totaled. This time around I got an XKR.

 

More importantly - any noticeable difference in handling?

 

my 2002 xkr coupe has the ss super sport option BUT the R handling pack was not available until 2003
Stevinson Jaguar in Denver called me yesterday to inform me that

R PACKAGE ROLLBARS & BUSHINGS are AVAILABLE: $811.00
I will post part numbers and labor costs in a few days in a separate post, so now we have some choices besides UltraRacing rear bar and do it custom by adding a second rear anti roll in parallel vertically