TL;DR

As title states I'm working on my 1989 XJS with the 5.3l HE V12 with marelli ignition

Engine seems very healthy despite being sat for nearly 2 decades. I’ve taken it down to the cams and want to check the valves and head gasket. Would it be advisable to remove the heads on my driveway with no specialist equipment or training. Please bear in mind that this is my first project car and if anything goes wrong taking the heads off I would be unable to afford to fix it. Is it worth risking, I feel like the heads will have to come off at some point as I have plans for a supercharger or two and will need to beef up the internals?

For more detail but optional reading:

First of all, is it necessary? The car was left sat for the best part of 20 years and the engine is horrifically dirty, covered in mm’s of grease, oil and other ***** that has built up in there in that time. However, before disassembly the engine was running an absolute dream, seriously this engine was built well, really well. I never ran it for more than about 5 mins to protect the fragile cooling system but when I did it started on the button every time, even after that big freeze we had in December when temperatures where I live were -1 for about a week. As far as I can tell there is no weeping or leaking of oil from the block, so I’d expect the gasket to be fine. However, when draining the coolant it was, brown, deep rich rusty brown (not oil just rust [I think, or I hope], and yes, the water pump and all hoses as well as the radiator will be replaced). I don’t know if this rusty brown coolant has damaged the gasket when it has been sat in the channels in the block, I’d think not as the coolant is not oily so there is no contamination between the oil and coolant systems, but I just don’t know. The engine has done ~84,000 miles and was serviced every 1500-3000 miles from 1989 to 2006. The last milage figure on the service booklet reads 81,000 in 2006. So its only covered 3000 miles since last service (all of which were done by Jaguar). Upon disassembly, the inside of the engine as well as any seals and gaskets I’ve removed so far seem quite healthy, with the exception of the injector seals (which will be replaced).

 

From what I've read: taking heads off is very tricky. You do need a special tool set to do so to pull the heads up. Go check out Camp Chaos Chronicles on youtube. He does good videos on teardown and buildup of a V12.

I would not take it down that far. Run it. See how it does. Check to see if coolant gets milky. Do a compression test. Avoid taking heads off if you can.

 

Put it back together and drive it. If it was running well, it’s fine.

Most of what touches coolant is aluminum and won’t rust, but there are a couple of steel pipes. That’s probably where you’re seeing brown coolant from. The pipes along the outside of the heads are steel, there have been stainless aftermarket parts available. Also the crosspipe that wraps around the front of the engine is steel. Not sure if there is a stainless one available, but as long as you keep on top of coolant servicing you should be fine.

If you’re serious about supercharging you’ll probably run into some bigger issues than just getting the heads off. The compression ratio is already really high, and the HE heads don’t flow that well. You’d be better off starting with a pre-HE engine. But get this running first and drive the car.

 

Absolutely no need to remove the heads. They will be hard to remove anyway, if not near impossible. What you will need to do is listed in the sticky at the top of the XJS forum page, post number one:
https://www.jaguarforums.com/forum/x...embers-235554/

You need to go over each system, replace anything that ages, and make sure it is OK with a car unused for this length of time (eg brakes, cooling system, injector loom, HT leads, CPS etc etc). If you have ABS brakes for example, these are complex and tricky to bleed, so search for anything under TEVES II most noteably from PTJS1 and Orangeblossom.

Supercharging the HE motor (the version you have) will burn a cyclinder crown or worse as the engine has an 11.5:1 compression ratio already and a combustion chamber that is entirely unsuitable for forced induction; futhermore packaging a supercharger is problematic under the bonnet and controlling the engine bay heat heat and coolant temps would also be very difficult in anything approaching a useable road car, as contrasting with a stripped-out, no-aircon, no-comforts racer. As the above post states, you need a pre-HE engine for that sort of development, which has a more conventional combustion chamber shape and a far lower CR. A guy on the Forum, Mguar, turbo-charges pre-HE engines and gets it to work fine in racing applications, so you can always ask his advice.

I would say that to get the car to reliable road status will be a decent amount of work, and covered space to work in is, in my view, pretty essential, when you need to do suspension bushes and subframe bushes and things of this nature!

I wish you all good luck with the car's revival, everyone is very helpful on this forum and an XJS when sorted out properly is a fantastic car to drive, which amazes people who have never been in a good one.

 

It may be necessary to take the hood/bonnet off to remove the heads, and doing that in a driveway setting would not be advisable. Not that it can't be done, more that it won't come off, work done, back on all in one day and keeping water out of the engine bay is a good idea. Its entirely possible to revive an XJ-S in a driveway, I've done it. I removed, rebuilt, and reinstalled the rear suspension in my parent's gravel drive. It wasn't exactly fun, but it was fine. I did the cooling system, brakes, and front suspension in the same setting.

 

if you plan on supercharging or turbo charging leave the heads alone. If the head gaskets haven’t blown they are sticking better than if you pry the heads off and put a new gasket in place.

Be darn careful with that stupid HE head. You start out at 11.5-1 ( 12.5-1 in England)
and 6 PSI. Is about as much as you can get by with. With the absolute highest octane gas available. Hopefully with ETHANOL. ( that’s the good alcohol). Alcohol cools down the inlet temp a lot. Compressing air heats it up and the hotter it is the closer to detonation you get. If it starts to detonate you have very little time before the engine is ruined.
Plus as you add air you need to add extra fuel or the engine leans out causing detonation.
You can’t modify the stock ECU to adjust for the added fuel so you will need to go aftermarket
Here in the states your 2 real sources are MEGASQUIRT and MAXXECU

The problem most people have with the factory distributors is the ignition curve. Which is designed to reduce emissions HE really stands for Help Emissions but marketing thought that calling it HIGH EFFICENCY. Sounded better. If you look the advertisement for power of the HE was the same with 11.5-1 compression as the pre HE with 7.8-1 compression.
Normally every point of compression increases 10 horsepower so the HE should have an extra 35 horsepower. But it doesn’t.

If you want extra power. There are other ways than SUPERCHARGING or TURBO CHARGING.
I like turbo charging because it adds the most power for the least cost. Supercharging requires careful alignment of the belt. Or you tend to throw off the belt a lot. Plus the added tension can cause issues with water pumps or other accessories.

I’ve done both. Once you go to aftermarket ECU’s and sort them out, turbo’s are a lot simpler. ( Superchargers sticking up through the hood are seriously cool though).