Numbers matching in a driver's car?

Hello all! So, I’m looking at two different xk120 FHCs, and have a fairly simple question: I’m looking for a car to drive (a lot). One of the cars I’m looking at is numbers matching and is in mostly original shape. I’d want to upgrade the front brakes to disc and put in an alloy rad/fan, as well as go thru the suspension, replace the bushings, etc. It has the original moss box, runs well, etc, etc.

The second car is a bit more expensive but has a lot of driver-type upgrades done: swap to a 5 speed, discs all around, alloy rad, shoulder seatbelts, warmed up engine, etc. But it’s a bodge of jag parts. It also runs well, etc.

My question is: is it worth (long term $ wise) getting the numbers matching car and doing a brake/rad swap and going thru everything, or should I get a car that’s got everything done already?

Or, more simply: how much does numbers matching matter for long term value. I can keep the original brakes and rad for the next owner, no worries there.

Thoughts?

Buy the non-numbers matching car. You don’t want to go down the rabbit hole of the whole numbers-matching thing. Buy it to enjoy it. Upon reselling, it may sell for a few grand less than a non-matching numbered car, but that’s only to those who care about such things. Typically a tiny minority obsessed with points at car shows and resellers using the matching-numbers ploy in an effort to extract more dollars out of a potential buyer. Just my take. I have one of each and value both equally well – just in different ways.

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Welcome Ben,
I’ve had my 120 FHC since 1980 and running since about 1992. The body has never been off the chassis. It is a driver, not a show car, and as close to all authentic original as I can get. I’ve put about 12,000 miles on it. I’ve never seen any need for 5 speed and disc brakes, and some conversions may not have been done properly anyway. I’m not a street rodder. It goes fast enough for me. My radiator has been cleaned, also the engine, and it doesn’t overheat. I had installed an electric fan but found I never used it so I took it off. I have an overflow recovery container that recycles the coolant back in when it cools off, so I’m never low on coolant. I have recently changed to radial tires and that has been nice, better handling and stopping distance.

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Thank you both, these are really helpful thoughts.

I guess I’d been told a bunch that overheating was a major problem without an alloy rad/electric fan (and drums are definitely drums… :stuck_out_tongue: ). But if it falls into the category of “nice to have but with some care, you won’t have any worries”, then I probably don’t need to do much at all to either car, and just need to make a decision, do a bit of haggling, etc…

Also, Rob, your car looks phenomenal! I love the ww with the fender skirts. All of the examples I’ve seen lately have the wire wheels/no skirts, but that is a heck of a look!

Thank you both, and I look forward to intoducing you to a new car of mine soon enough!

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What Mr. Potempa said!

:grimacing::+1:t2:

@epicrabbi , I went through similar questions over the last two years of searching for the right XK120. For myself, I value originality, and I did appreciate finding a “numbers matching” car. I had already set my other requirements - it had to be a FHC, and had to be steel wheel + Spats. Then it was a matter of patience waiting for the right one (at the right price) to come along… If I were in your position I would pick the more original of the two, then drive it and get comfortable with it before launching into upgrades… While I have only had mine a few months, my feelings echo those of Rob Reilly.

I guess it comes down to - do you want to experience driving as it was “back in the day”? Then stick with the original mechanicals and brakes… If you want a more modern experience with the look of an XK120, then go with the updated mechanicals. And if you are like me, and hold your cars long, then also think a little about - what is going to make you happy in 20 years time…

Here is what I wound up with. A few teething problems (yes, overheating!), but I’m pretty happy… I added seatbelts as my first upgrade, but other things I am working on are to take it back to as close as original as possible…

@Rob_Reilly , interested if you could share a photo of your overflow tank installation. I think I tracked my original overheating down to a bad radiator cap, but definitely lost a lot of coolant (1.5 gallons) on my first long run.

Chris.

I love the comment “matching numbers” you see this comment regularly and the note re matches heritage certificate but more than one of these has become matching numbers after someone has ground off other numbers and stamped matching numbers on!
Caveat emptor

Yes. Sadly, that does happen. When once shopping my block and head out for a rebuild, a potential rebuilder pointed out “flaws” and said he’d be happy to supply a replacement block and re-stamp the numbers so, “No one will ever know”. I scooped everything up the following morning and couldn’t get out of there fast enough. I’m in this for the love of it only and looking back, I still shake my head over the display of blatant greed and dishonesty. Thank god characters like that have been few and far between in my experience.

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I think this will fall into the category of “things you probably shouldn’t lose a lot of sleep over…” I’ll be as honest with my record keeping and let the rest go.

After all, if something I own winds up under the scrupulous eye of a concours judge, I have made a dozen wrong turns somewhere…

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Hi,

In case you just check, you’ll find that I went through the same process only 2 months ago (In the process of buying an XK120 FHC - #39 by LLuis_Gimeno).

I bought a matching numbers car (except the head), that happens to be in very good shape. Although I cannot of course be sure that someone re-stamped the block, chassis and gearbox, everything does seem original.

For me the decision was in part similar to yours, I had three further candidate cars fitted with MkI, II and MKVII engines. The one with an MkI engine was incredibly fast. But now to what matters:

  • Body and Chassis wise all cars were exceptionally good
  • Mechanically all cars were really good (I did now more than 1000Km in mine, no issues, but lots of preventive maintenance
  • Steering and brakes are really good in a XK for anything that normal traffic can give, really much better in any case that what even reputed classic car journalists write.
  • No overheating what so ever
  • Final Drive is short for modern-day highways and the torque of the XK engine. The 5-speed is an option, but it needs chassis-cutting → Why not try a longer final drive (2.88) in case you go for an original car? It would bring 2200rpm / 100Km/h instead of 2800 rpm, which I admit is boomy.

BEWARE or thinking modifications before you own the car. At the end I am really glad I waited. The only change I did (other than an Aluminium radiator for no real reason) is the 123 ignition (and yes, I recommend, from 3800rpm at least in my case it has noticeably improved smoothness).

Buy the best car you can find, matching numbers will inevitably fetch higher values, also longer term, but I would certainly not have bought a matching numbers car in need of major work, rather a well-appointed non-matching, in my case it’s just that I found a matching-numbers that I liked.

Best,

Ll.

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I have a numbers matching xk120 w original brakes, transmission, no alloy radiator and no electric fan. I still have mechanical points in the distributor and positive ground electrical.

The car never overheats in up to 36C in moderate stop and go traffic. It can lock up all four tires anytime I push hard on the brake pedal. It drives easily in modern traffic, up to 145kph.

The only modifications are (1) fresh engine rebuild, (2) fresh restored drum brake system, (3) 3-row recored radiator (4) modern radial tires on modern manufactured wire wheels

I think an electric cooling fan is a good safety feature, as is an alternator hidden inside the body of a generator. For my needs, very few modifications are necessary because I am seeking a modern driving experience with vintage cosmetics.

So, as advised, decide what experience you want and then pick the car. Value, I think a well modified car has similar value to an original car so long as you are below a 99.5 point show car level. At that #1 condition level, original configuration becomes important and the modified car will have less value.

John

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my xk120 has no significant modifications…I drive it a lot. does not need disc brakes…it stops and can lock up if needed…discs help if many stops in quick succession or rain. Does not need 5 speed, tho I do want to have a taller diff ratio…than the 3.54 as I like a tall cruise top end. Has no cooling modifications…yes they heat up in traffic. It has the original engine block…not orig cyl head…not something that matters to me either way. I will drive it until I am too feeble to drive…then will go look at it in the garage and fiddle with it. A thing of beauty is a joy forever…Nick

Hi Benjamin,
Here are my 2 cents (or pence).
I’d dissuade you from going for the modified car, as I find when properly set up, the brakes and cooling systems on these cars are quite adequate for even hard driving. I also find the old Moss gearbox to be part of the car’s charm. I’m the third owner of a numbers matching XK140 MC OTS. I was lucky to find a well cared for and cherished car from a fastidious owner. I tend to drive my cars pretty hard on occasion and spun a bearing while pushing on shortly after acquiring the car. I sent the engine out for a rebuild to Bill Terry of TT Performance Engines that has been building racing XK engines for about 40 years. I asked him for a spicy street/performance build to suit my driving style. The engine dynoed at 250 hp, runs very strong, and is now back in the car. As I mentioned I push the car harder than most probably, and plan on taking it on a few rallies. Below is my assessment of the Brakes, cooling system and original Moss gear box for spirited driving.

Brakes:
I rebuilt the master and slave cylinders, turned the drums and replaced the brake shoes. The drums do take more pedal pressure than a disc brake system but pull the car down nice and straight and will lock the tires up if pressed. I find them perfectly adequate, once you are accustomed to the required pressure for a hard stop. Don’t just throw the keys to a friend and say have fun though.

Cooling system:
I had the original radiator cleaned, flushed, repainted, and pressure tested and it works completely fine. I also replaced all the hoses and thermostat. The car actually runs a bit on the cool side staying below 70c, which I verified with a handheld pyrometer as I was suspicious of the gauge in the dash. My car came from the prior owner with a modern coolant overflow tank on the left side of the engine bay and also an old E-Type style electric fan in front.

Gearbox:
I enjoy driving the car with the original Moss gearbox. 1st gear is non-synchro of course and I only use it from a dead stop. If I’m still rolling at all it’s 2nd gear. The car has so much torque that’s never a problem. I love the whine of the straight-cut gears in first. With my sporty engine the car really gets lively above 3,000 rpm. That combined with double clutch downshifts really makes it engaging to drive. It’s really rewarding to go up and down through the gears the way the car likes without a crunch. To me, this is all part of the charm. It’s how it was in the '50’s and I personally wouldn’t want to change either the brakes, gearbox, or cooling system on my car. We’ll see what I think after a few extended rallies though.

Other modifications:
I’m 6’3" with long legs and am making some modifications to improve legroom a bit. I removed the period Blaupunkt radio, which hung below the dash and interfered with my right leg when braking. I’m also getting some shorter brake and clutch pedals to try. I upgraded the brake and tail lights to LED circuit boards which are much more visible. I feel this is a very worthwhile safety enhancement. I’ve also installed a positive earth alternator within a generator shell. The car now charges nicely at 14v and gets me home comfortably at night.

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Thank you, everyone. These are really helpful thoughts.

I wasn’t really thinking about swapping out the trans. It’s just that the other already had the swap, so it was a thought. (tbh, if I was gonna swap the 4 speed box out, I’d probably look for a sequential shifter. They’re definitely my favorite kind of manual trans… :slight_smile: )

And it’s great to hear that so many of you are able to drive without too much worry about overheating or stopping. That makes me feel a lot better.

My thoughts, for now, are to go with the more original car, mostly because I think the body is in slightly better shape and the price difference (the numbers matching car is actually a bit less expensive) will allow me to do some preventative maintenance…

I’ll probably still do an electric fan on a toggle, just because I will do a little driving on sunny days in traffic, a gen/alt swap. And I can spend a bit of time with the drums (I have drums on all 4 corners of a '54 Hudson of mine, and have always found them to be adequate, although I suspect I’ll be driving the jag a bit harder than I do the Hudson…) and if a swap is necessary, it’s all bolt on stuff, so no long term loss of ‘original’.

Any advice for a thorough cleaning of the cooling system?

Any any other weird niggles I should look for as I do a final inspection, specific to these cars? I’ve done a compression/leakdown test, no leak from the rear main seal, trans shifts well without grinding, and the body is remarkably rust free. Anything else specific to XK120s to look for before buying?

Thank you all!

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Cooling: If In doubt, I would record the radiator with a three row HD core. Make sure you have a proper thermostat and consider a flow restrictor in the bypass hose.

Stopping: If the drum brake system is working correctly, your limitation in braking performance will be tire traction. Stickier tires will give you shorter stopping.

Did you check for wear in the door hinges?