XJS prep for 24 Hours of Lemons

So this may be better suited in the racing forum here, but since it’s XJS specific I thought I would ask here first.

So I’ve raced in the 24 Hours of Lemons for many years, built 3 race cars all cheap Japanese cars. It’s a endurance road race where the cars “cost $500.” But I’ve recently become obsessed with building a V12 Jag.

Collective wisdom over on the Lemons forums is the Jag V12 is a terrible idea, which they of course encouraged it. The only team that has run the 5.3, at least that I can find, has serious problems with keeping head gaskets together. From all the searching and reading I’ve done, my working theory is that this is probably due to cooling issues inherent in these often neglected motors. It also seems that they tend to lean out causing detonation issues if the ignition and fuel system isn’t perfect. I also read somewhere that the water pump is prone to cavitation at high rpm.

So I would love thoughts on keeping this motor happy under budget race conditions.

Obviously the other issues would be weight reduction, brakes, suspension and handling. But those would all be secondary if I can’t keep the motor alive.

Thanks in advance!

Welcome to the forum Bob, I applaud your madness :slight_smile: there are numerous threads relating to the cooling system of the 5.3, one Norman Lutz has a mod that restricts the flow of coolant to the front of the heads and sends more to the rear which I believe is what you are going to need. One other mod I would suggest is a tow bar for the mini fuel taker you will need to minimise the fuel stops.(said with tongue firmly in both cheeks)
Look forward to the progress reports.

It will be great to prove them wrong !
Sort out the cooling, new rad, Lutz mod, correct thermostats
Sort out the ignition, new amplifier, distributor and advance overhaul
Sort out your fueling, clean tanks, new pump, filter and ad inline filters before the pump
Get rid of all the extra weight and you are good to go !!
When sorted out, these engines are happy to rev all day long.
As Robin said though, fuel sops might be an issue… said with tongue firmly in both cheeks…

I see an IoE in your future, mate…:grinning:

For those unaware of what an IoE is…:wink:

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Run some acid through engine without the stats then flush. Moble 1 oil, striper down, torque the heads, take a lot of gas and she will run all day. They tested the new HE engines by running them at 6000 RPMs in Italy for five days!

Keep us posted! …good to see a LeMons team, flying the Jaguar banner!

Well I’m picking up the car Friday. Fingers crossed it’s not terrible.

Thanks for the guidance. Especially re torquing the head bolts. That wouldn’t have occurred to me.

This brings back memories of a group of guys from the Ontario Jag club that did Chump Car racing a while back.
I was just a tag along.
Here are some pix from Watkin’s Glen.
They have since given up. It was getting hared to trailer the cars around, the guys were getting older, and they were discouraged with the costs: new helmets and seat belts every few years etc.
The XJ40 ran well but was slow. The XJS was fast, but suffered many issues. Swapping to outboard brakes was a must for endurance races, and they did mega-squirt. They encountered the shielded ignition amp-to-ECU wire intermittent shorting issue; that’s something rule out for sure. They used the T400 with shift kit. 3.54 diff. Solid mounts, rear anti-roll bar.
That’s all I can think of at the moment. Good Luck,

Yea: even if MANY bags of money fell on me, the memories of the trailering/upkeep/ maintenance, even of a “cheap” race car like a LeMons, is enough to put me off.

For a LeMons effort, I’d prolly go for a seat buy-in!

@Robert_Laughton… how much to buy a seat in your car? :grimacing:

Since the outboard conversion is a must, what’s the best subframe to swap in? From my searching it seems that there is broad compatibility aside from the handbrake being an issue which doesn’t matter because race car.

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The Ontario guys used a late XJS IRS. They got the 3.54, anti roll bar and outboard brakes in one go.
Alternately, using XJ40, X300 or maybe X308 hubs can be installed, using a 1/2 inch spacer where the disc used to be. There will be lots of info on this. I imagine the latest vented disc units would be best.

If you go ahead, I hope you’ll post pictures here.


For the later hubs you will also need some metric bushings to fit the fulcrum shaft on the outer lower arm. I had some aluminium spacers and bushings made up for such a project, but the handbrake issue (a must for a UK road car) was too big a problem, so a 1994 axle was the best way to do this.

No, I don’t have the parts any more. I sold them to a guy with a De Tomaso who said it was the same IRS :thinking:

The disk was 3/8" thick. Of course, one simple way to obtain a spacer would be to cut off the outer portion of the original disks.

So I pulled the trigger on this terrible idea. May god have mercy on my soul.

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Ye gads, that sounds like fun! We expect not only copious photos, but videos as well!

Roll the rear fenders, and put some WIDE slicks on that baby!

You can do the trick of rolling the fenders with a baseball bat.

Rather than going to the expense of replacing the IRS with an outboard brake setup, you might just rip out the back seat and cut a hole in the floor for replacing the brake pads. Maybe two holes. I presume a pad change will be needed in 24 hours of racing?

Just saw the air horns off the air filter boxes. You can relocate the air temp sensor into the air box proper.

Drop the downpipes and gut them.

Yank the air pump, install a CS130 alternator in its place with a large diameter 5/8" v-belt pulley on it. Eliminate the OEM alternator along with the belt that drives it.

I think I’d add a transmission cooler.

Now that it’s in my garage and I can start giving it a good once over, the first order of business has to be finding the overwhelming smell of old gas that now fills the garage.

Good luck Bob on your racing adventure - even though you may be posting on the racing forum, can you come back here to advise where you find the gas smell coming from, as well as updating your changes (as mentioned by others) - what year this XJS.

This is going to be used as aLeMons crapcan?