Electrical upgrades for a '52 XK120

[Tim_Creger]

I've got a friend here that recently inhereted a 1952 XK120. It appears to be very original, save for one repaint job 10+ years ago. He would like to tune up the electrical and carburetion system to help it start and run better. Could anyone tell me if electronic ignition is a regular modification, and what else should I be thinking about to "liven up" the old beast? I've got good experience with older Sprites, but not Jags.

I'd also like a good link to any online manuals you all might know of, and a parts house wouldn't hurt. I've only seen the car once, and don't even know where the dang battery is at!

Tim C.

 

[mikespain]

If the engine mechanically is in good condition then if its been sat for a while I would clean out the fuel system,including carb strip,make sure the distributor is in good condition renew the points and fire it up,and tune the carbs in,these engines if tuned properly start easily and run very well and smooth.Personally I would not put electronic ignition cos if kept up to scratch the original system is very reliable.There is a lot of info about them on "jag lovers forum"The batteries (should be 2x6volt)are behind the seats

 

[Exotexs]

I too would stay away from electronic ignitions, Pertronix in particular appears to cause electrical harness meltdowns.

No manuals online, as in "free". it is prohibited by Jaguar. You need to buy one, around $25.00

try: https://www.lbcarco.com
click on books, then click on Manuals on CD.

Parts for the XK-120: Moss Motors has a nice catalog:

https://www.mossmotors.com

SNG Barrat USA too.

https://www.sngbarrattusa.com/


there are other vendors I do not recommend due to bad experiences like bad quality parts and bad customer service,
so Caveat Emptor.

Ex

 

[Tim_Creger]

Thanks for the reply - I'll look behind the seats for the batteries. As for the car and engine, the current owner immigrated from South Africa 10+ years ago and this is her father's car she recently inherited. She decided there were many fond memories riding in it as a youth, so wanted to keep it in the family. They shipped it over last winter after having someone there prep it for transport. They did everything right except forgot to drain the radiator, which subsequently froze and split open in transit (lucky it was only the rad and not the block!). That's all been repaired and the car, once it starts and warms up, runs well. The issues it has right now are hard to start and rough running until warm. Sounds like standard carb/dizzy issues. I am totally unfamiliar with the "pre-start" carburetor this thing has, so that is why I am looking for a manual. Is that thing made by SU like the main carbs, or someone else?

Tim - Lincoln, NE

 

[Tim_Creger]

Ex:

Thanks for the reply, and MAN! THANKS for the heads-up on the Pertronix EI unit. I've not heard of that happening before, and since I am a fan of the systems in other cars, I would have spent the bucks on one just to watch it let all the smoke out of the wires! :shocked:

I looked for a Moss catalog but didn't see one, so must've been looking in the wrong place. Guess I can call them if I have to. Also appreciate the lead for the manual, that should really help me understand the differences between this car and what I already know.

I agree about the point you made about avoiding poor parts sources; they are to these cars what off-shore telemarketers are to customer service.

Regards,

Tim - Lincoln, NE

 

[DrEntropy]

Tim, is this the electric solenoid choke device you're calling a "pre start" mechanism?

I've a factory manual here and may even be able to FIND it.

 

[jessebogan]

First, check the "ottrt" switch on the intake manifold water rail, near the outlet for the top hose. It is held on by 3 little screws.. It should have a single lead attached. If not, it may have been converted to a manually operated switch under the dash. A VERY common conversion.All the starting carb is, is a solonoid that is activated electically. It opns an air passage, and inlet mainifold "depression" pulls the fuel up past the needle that you see. It shares fuel with one of the float bowls on the carb.

I have a friend/customer with a 54 120 that he drives all over the place to shows as well as for entertainment. He fitted a pertronix several years ago, and has had no problems with it at all.

I have some luck watching Ebay for NOS lucas parts. They fit, and they work like they should, all Lucas jokes aside. I HATE repro parts with a plu perfect passion, so I am relly glad to have the amazing internet as a resource. Real parts beat fake parts every time, so be patient, and see what turns up.

Happy motoring

 

[Tim_Creger]

I don't know if what you describe is what I am calling a pre-start carb - that's just what the owner called it. But just from the name you gave it sounds like it might be the thing. If I can get my hands on a shop or owners manual I will probably be able to figure it out. I'll get back to the list once I figure out just what the heck it is I'm talking about!

Tim

 

[DrEntropy]

Tim, it's almost certainly the solenoid giz Jesse and I are talkin' about. I'll scan th' relevant pages (SHHH!!) and we'll get 'em to ya.

 

[MGZT260]

Pre-start carb certainly sounds like it may be an electric choke. Some method of enriching the fuel misture at start until warm-up is required.

As for simple breakerless ignition I have had nothing but success, whether changing a 'B' from cranking for almost a minute to firing off within literally seconds, or even on a farm tractor where it successfully countered the ravages of time that left us with a sloppy distributor shaft that had caused bouncy timing. It is the best improvement for my money that is so easily returned to stock for concours.

 

[Exotexs]

it is called the AED (Automatic Enrichment Device) and it is also called ASC (Auxiliary Starting Carburator). Also called
an AC (Automatic Choke). Jaguar used them through 1973 in the Series 1 XJ-6 and 12. So for the first time in the history of mankind, EVERYBODY is correct!

My '65 S type has one. They spit on you as you get near them when they start "hissing". They come on even when not needed (car has already warmed up!). Some modifications include an under-dash switch to turn it OFF. Some Jaguar owners take the Pull Cable Choke from an MG-B and adapt it to the Jaguar carbs. (my first car was a 1969 MG-B so I know and love those old manual cable chokes). Yes, they are powered by the Temperature Sender, (otter switch), as stated before. Yes, they were an SU/Lucas invention. They do get clogged, they are adjustable if you know how.

The man to fix it is called Joe Curto in NY.

https://www.joecurto.com

He restores SU and other carburators.

On the rough running symptoms, it could be anything, including a vacuum leak, a bad ignition condenser or points, rotor, cap, loose spark plugs, coil, stopped-up fuel filter, sticking carb floats. Ad infinitum.

But one thing is sure, these cars are very simple to fix )

Ex