The pre-HE cars used 205/70x15.
HE cars used 215/70x15 for several years. Circa 1988 Jaguar began using 235/60x15 for a few years.
Circa 1992 some cars were fitted with 16 inch wheels and fitments were a bit more complicated ....and too difficult for me to sort out when I'm not yet two sips into my first cuppa coffee

Cheers
DD

 

Entry on-ramps to the main freeways and highways are our friend here in the 'States. Excellent opportunity for a run right up to 6500RPM in first gear to clear the pipes, so to speak. After all, you want to be at highway speed when you merge into existing traffic, right? It's the safe thing to do ! You owe it to society to not dawdle

I use my car as a daily driver and it sees lots of low speed city driving. Poor thing gets congested quite often.

Cheers
DD

 

At least if you hit the freeway running hard, nothing can hit you from th back!

 

the “lumpy” tick over is most likely due to deposits on the back side of the intake valves.
The expensive solution is to do a valve job.
The better solution is to use 10% ethanol gasoline to clean off those deposits. The faster the engine goes the sooner the deposits are washed off.

How does that work? Take a glass ashtray. Or something about that size made of glass. Fill it full of gasoline and carefully light that off. The deposits on that glass are just a tiny example of the crude deposited on the back side of your brake valve. ( remember the injectors are batch fired and the camshaft decides when to open the valve and let that gas enter the cylinder )
Now do the same test with Ethanol.see the difference?

And No!! Ethanol will not hurt your car. It may clean out a gungy fuel tank so you might need to replace your fuel filter a few times.

 

Doug please read my comment above. Ethanol is your friend. It does a much better job of cleaning deposits than Has does.
Remember Jaguar’s fuel injection is batch fired. Only the camshafts determine when the fuel goes in. So the fuel/ air has time to separate. And land on the cool intake valve.

 

I've been using E10 in my Jags for 20+ years.

But the car spends 1/2 its life running on the cold enrichment circuit. Still needs an Italian Tune-up from time to time!

Cheers
DD

 

Well done Doug. Italian tune up on freeway on ramps are an excellent way to help remove those deposits.
I’ve tried most of the EFI suppliments and they don’t help nearly as much as a good romp on the freeway on ramp.
Have you converted your automatic transmission to manual? How can you get it to hold in 1st gear all the way to 6500rpm? It’s a simple task with the Turbo 400 just drop the valve body and follow the procedure on U Tube. While you’re in there you can boost your line pressure up so the shifts are instantaneous.
That does change the car from a civilized cruiser to something more direct?

 

Manually select "1" and shift at 6500 RPM

When I had the transmission overhauled I asked that a mild shift kit be installed. It changed some of the operating parameters.

Not really, no. In gentle or moderate driving the difference in shift quality isn't at all objectionable; it's barely perceptible. Only under heavy throttle is the difference pronounced.

There are a slew of mods and shift kits out there. It's easy to go overboard in this area....as I learned many years ago

Going with the mildest versions works well for most drivers

Cheers
DD