I just bought a 1978 XJ12L. It was originally bought so that
I could de-lump my 77 XJ12C but I kind of like it. The
fellow that I bought it from was a pretty nice guy. He is
selling it on behalf of the wife of his late boss.

He's a one owner car and he remembers putting a water pump
on it back in 1985. He said his boss stopped driving it in
87 when he bought a grand wagoneer (which he was also selling).

The car is complete and straight but has some surface rust
on the roof and obviously has not been run in 25 years.

As I already have a V12 engined XJ12C, I thought this may be
a nice compliment to it so i'm debating whether to sell my
chevy powered car and keep this one.

With all that said, where do I start?

 

You'll likely need new coolant & heater hoses too, maybe a new belt/s.
I'd begin with ALL new fluids. Brake fluid, Coolant, Engine oil, Re-lube the wheel bearings, Tyranny lube, Drain the gas tank & the fuel lines, if the old gas is still in there, ya gotta get rid of it.
Refill the tank with fresh gas, with 0.4 oz per gallon of Marvel oil mixed in with the new petrol. After you run a tank or two through it, I'd change the fuel filter too.
I'd remove the spark plugs & squirt about 4 tablespoons of Marvel Oil in each cylinder & let it sit over night.
Then remove the plugs & disable the spark.
Then crank the engine for maybe two 15 second periods, (so as not to overheat the starter) to distribute the Marvel oil in the cylinders, build oil pressure & prime the fuel system.
Then replace the plugs & enable the spark & start her up.
Don't try to roll the car, as the wheel bearings may be welded from all the vehicles weight being on them this long, clean & re lube them first.
i don't know what to tell you about the tires, as we don't know under what conditions it's been stored.

I found all this on answer dot com but couldnt get the link to work

 

I'd suggest that the first thing to do, is to post some pictures of all three. Then we might be better able to help with your decision process.

Whatever you do, you do not want the engine to fire until you know it will spin and good oil is getting around the place.

From the above, after 25 years the tyres are goosed, even if they still contain air, they are out of date for safety and insurance purposes and need to be junked.

 

Thanks guys,

First thing will be getting the engine running and making sure that can ran and does not knock. Then I plan to go through the brakes, belts and everything else in order to make it into a driver. Marval mystery oil (or ATF) in the spark plug bores and the gas tank is a great idea.

For pictures, here is the car the car:


This is my silver 75 XJ12C, also with a V12 but has been converted to run on propane.

The red one is now on ebay, this is the car with the small block chevy.

Jaguar : XJ12 | eBay