I needed to move the '88 XJS from off the lift, over to a different part of the garage where the engine/trans could be pulled.

I had already removed the exhaust system while it was up on the lift. I figured just drive it over to a place where an engine puller could be used.

So, i get in, and am ready to hear the thunder of a Supermarine Spitfire MkIV Griffon V12 , engine fire up, and instead I get a putt, putt, putt out the open exhaust manifolds, though some what louder that thru the mufflers. LOL

I guess being shy about 1400 cubic inches makes it a little quieter.

Doug

 

The exhaust valve is the muffler. It opens late and closes early.

 

And only opens 3/8ths of an inch at max lift.
On top of that the piston is only 3&1/2 inches and the stroke is a mere 2&3/4 inch.
But it’s massively overbuilt. Connecting rod bearings are a relative massive 2.300 and the main bearings are 3.00. ( those are big block V8 sizes ) further proof that William Lyons intended to take the engine out to 500 cu in.

As a result these engines really don’t wear out.

 

Those crank journals are larger than big block chev journals. BBC is 2.20", and 2.75", IIRC

500 cube overhead cam V12, wow, that would make for a fun XJS.

Doug

 

The 5.3 goes very easy and cheaply to 6.0. Offset grind the crankshaft to 2.100 then bore out the sleeves to as close to 3&3/4 (94mm) as you dare.
There are racing Chevy 6” con rods that very affordable. The rod end and bearing will need to be narrowed to the Jaguar width.
94mm is a pretty common piston size. If you find a Chevy piston you won’t even need to worry about pin size.
Make sure they are dished pistons. You’ll want to use the early pre HE heads they flow massively better than the HE heads do.
Both ISKY& CROWER will regrind the camshafts. ISKY’s XM3 is a decent 3/4 race camshaft that still idles smoothly at stock RPM
The XM. 4 is as aggressive as you should go with a regrind. If you want serious power though, aftermarket billet cams are the only way to go and they are more expensive than they sound.
If you’re looking for the 7-800 horsepower area, good port work, bigger valves ( intake and exhaust) Are required.
Weber 44 IDA’s are required but will not fit under any stock hood. The IDF’s will but they are too short. Unless you’re looking at 9,000 rpm as peak power.
One other solution is you can go as large as 48 DCOE’s if you’re using E85. Instead of gasoline.
Fabricating the manifolds will be up to you though. Those can fit under either the XKE. the XJS, or XJ12 hood ( bonnet).
The cheapest and easiest way is to put a pair of EBAY, or AMAZON T2 turbo’s. ( $130 ea. ) They really work well with the preHE heads and lower compression. If you’re going to use them with the HE heads you will need either an air to air intercooler for each side and 105 octane race gas or E85 in either case you will need a boost limiter for each one ( $55 ea) if you’re racing you should put blow off valves.
Stone stock. Untouched engine you can get around 600 ho and tremendous reliability.
Cams and a few other minor things can get close to 800 horsepower. With a pair of turbo’s.

 

What would be your top 5 items if you were to acquire an absolute stock HE V12? Remove a bunch of the OE stuff like air pump etc.?

 

Wow! That’s a lot of work to make the V12 louder…

 

Depends on your goal. There isn’t very much power to be gained by their removal. But it sure does clean up the look of the engine.
For power gain, the camshafts are the first and easiest item to deal with. But like everything they are a trade off. They won’t gain you anything at low stop light drag racing sort of RPM. The power gained happens at 3500 rpm and above.
The next item is a pair of cheap EBay turbo’s. They easily double the horsepower. But to work you’ll need to replace the ECU. The cheap ( and easy to work with) is the Megasquirt.
I know they are scary. I was working with carbs and mechanical fuel injection back in the early 1960’s. But if you want just some of the power available, in the end that’s the cheapest and easiest way to gain it.
Every other approach gets too expensive, too fast. Weber carbs and manifolds are about $3000 new but require at least another $2000 in tuneup parts. Plus time on a dyno to get things to work together. Those used sets you see for sale occasionally are because the owners didn’t understand what it takes to make them work. ( hint; it’s not just bolt them on).
I’ve seen manifolds with a pair of Holley carbs. Yes it will run. But no real power gain over the stock manifolds and carbs. (( ask me why if you want). Stromberg carbs are lawnmower simple.
Get someone who actually knows them and you will learn everything in 15 minutes.

 

The goal isn’t the volume of noise. But rather the power gained happens which as a by product of those changes starts to make a beautiful sound.

 

I guess my personal goal would not be horsepower but more giving the engine a better appearance. Reduce the crap bolted onto it. Reduce or hide wiring etc.

 

Opening the hood of a late '80s XJS engine compartment is like going into the house of hoarder,and you know that there is Loius XIV furniture somewhere under the piles of junk.

Doug