I very sadly made a huge mistake last week...I drove my 49k miles 1985 jaguar xj6 after its water pump belt broke, with a broken thermostat. Engine overheated catastrophically, I'm not getting any compression in cylinders 2-6 and only 52psi on cylinder 1.
So, I figured this is the best time to do what I've been thinking about since I got the car; AN ENGINE SWAP! I just feel like the xk6 is just slightly underpowered, and the 3 speed automatic transmission in the series 3 is less then favorable...if I were to pair a durable, powerful engine with a smooth transmission in this Jag it would easily become my favorite car I've ever drove. My question for the forum is what engine should I use? I've heard of tons of people using chevy small blocks or ls engines, but I'm not certain these engines will be adequate for my application. Here are some requirements.
1)need to get at least 20 mpg average
2) needs to be within 180-300hp+torque
3)needs to be an engine known for its reliability; this will still be my everyday driver
4) the lower the miles, the better! I have no idea where shop for brand new engines. I'm not about to go through all the time and money for an engine swap just to have to rebuild the 200k miles hunk of metal a year down the road.
5) most importantly, it needs to be affordable. I'd like to spend no more then 4k on this whole project.

Any and all insights are welcome!!

Engines I've looked at:
4.8 ly2
4.8 LR4
Small block chevy
a V6 from a 1990's nissan

 

I would NOT condemn the engine that came with teh car.

The Series 3 4.2 of my Son, survived his teenage era and he still has it at 38yo (him not the car) and 420000kms.
The Daughters S2 4.2, God knows the kms, but a shiiit load, and she still has that.
Our S2 V12 (1976) 652000kms.
Our S2 Daimler 4.2, 380000kms, still fine with its new owner.

We do Serious kms, and the Jags have NEVER failed any of us.

OBVIOUSLY, maintaining ALL the cooling system when the car first appearing in the fleet, and keeping an eye on things on a weekly basis, and when driving, LISTEN, for odd sounds and fix that issue NOW.

ALL these cars have traveled all over Australia, and our summers are HOT, and they have no issues at all.

Guy I know, a long time ago, did the maths to put a small block in a S3, and the $$ simply did not add up, and the Jag engine was rebuilt (overheated like yours) for half the $$, and is still running. OK, LS1, LT1, etc etc were NOT around back then, so he was going carby, so fuel system changes, trans change, final drive change all added up to a no go.

Clearly, it is your choice, and what is out there in YOUR market will dictate what if possible. Looking after that car, Jag engine or not, is the prime failure in my opinion.

I too often hear, "I will get to that later", and LATER is what has just happened to you, SAD, but avoidable, no matter the power plant under the bonnet.

 

New engine? $4000 budget? Probably not possible.

Will this be DIY project or will you be paying a shop to do the conversion?

$4000 will disappear very quickly

Cheers
DD

 

Even though I am rebuilding a 1985 S3, I have zero experience with the XK engine, I've never even heard one run. I do, however, have a great deal of respect for many of the experts on this forum, Grant among them. I'm under the impression that this engine can be made to run forever, if you do your part.

That said, your "requirements" for an engine swap describe the 1990's fuel injected small block Chevy to a "T". Although my experience is limited, I suspect the same can be said for an equal in Ford and Chrysler families. I am swapping a 1994 Chevy LT1/4L60e into my S3 and because this will be my last car project, I have set the bar very high compared to mechanic's that would just get me to the store and most of the way back.

 

Damn! hit the wrong key.

In closing, I will have about $7000 in my engine, $2000 in the transmission and north of $9000 in the car before I get to drive it for the first time. Swapping another engine/trans into your Jaguar is not cheap, but it can definitely be done for something less than my example. The biggest thing you should positively decide is what do you want the car to do for you. Reliability, Speed, Racing, Prestige, Bling, Faithful originality, or whatever.... They all take a different path and have different costs.

Rebuilding the original XK is probably the cheapest and would have $0 swap expenses.

Dave

 

I forhgot alos./

ANY Fuel Infected swap will need an engine management system, more $$, and an Electronoc Trans, another ECU, more $$, then the fun of getting them to talk to each other, more $$.

Rebuild that engine, last one I did was 15 years ago, S2, so extra machining for "stepped liners", and I balanced the whole engine internals. Parts and machining, $2500.
Labour, FREE, I never get paid for doing my own work/engines, bugga.

That was the Daughters S2, and she apprenticed in the rebuild, coz SHE broke it, not me. I told her the bottom LH radiator hose needed changing, "I will do that soon" was all I got.
Thats the one above that has done "shiiit loads of kms", and still sweet as they come.
She learned, and keeps on top of anything that looks suspect, Husband (was boyfriend) can wait in line, taught her well.

 

As mentioned earlier If you're going to do a swap I would go with another XK engine from a SIII car - it's the fewest number of variables to deal with.

It may be worth pulling the head as a forensic exercise. These engines are relatively simple and tough so the problem may be fixable without going through an engine swap.

Don't know where you live but David Boger (Everyday XJ) might have a decent long block assembly.

 

I myself would want to pull the head for a look-see.

But our OP mentioned in the previous thread that this is his only car and he has no place to perform DIY repairs. And also mentioned that the oil and coolant smelled "very burnt"....which doesn't bode well.

Installing a good used Jaguar engine would be the easiest and fastest way to get the car back on the road and should come in under the $4000 budget even assuming paying a shop to perform the work. David can probably come up with a good candidate. Of course, the life expectancy of a used engine...even one that sounds great and runs really well...cannot be positively known or guaranteed. So, there's some risk involved.

Cheers
DD

 

Once an engine over heats that bad it's trash. The pistons grow and skuff the bores then metal get in the filter, clogs it and then and the bypass opens, allowing the oil to bring metal all over then engine wiping out every surface.

The only engine that easily ticks all the boxes is an LT1. Since I'm experienced I could probably pull a running install off for 3k so 4k isnt unreasonable for a 1st timer. Stock B body LT1 with iron heads have very mild cams and are very smooth and sedate and offer up fantastic mileage with just under 300 HP.

Your 2nd best option is a 4.8 / 5.3 LS. You might be able to pull it off 4K only if you had a complete running donor and lots of time and experience with LS swaps.

 

Remove the head and inspect the cylinder bores for scoring. Check the cylinder head for warpage prior to condemning the engine.

If the engine is unserviceable, find a used 4.2 litre XK engine and install it into the vehicle. Less trouble than attempting to lump the car.

Since you want more performance, it may be best to find another car such as an X308 with a V8 engine.

 

It seems to me that the first thing to do with this problem is to lift the head and have a look, before any decisions are made on future remedial action. Maybe all the inlet valves bar one got bent. Bent valves are usually detectable just with the cam covers off - measure the tappet gaps, any that are very large is a bent valve. Bent valves will totally prevent any cylinder pressures from being created. It is very rare for overheating to distort what is a huge piece of cast iron, but the aluminium cylinder head is another matter.
For me, "act in haste repent at leisure" needs to be borne in mind. I managed to remove the engine and gearbox from a Series 3 and rebuild it inside my quite small garage, but the car had to stay outside of course. However, if XJ6baby has no garage, sorting things out will be much more difficult.

 

1. busted thermostat? I see the only way that had any efect was id it was stcuk closed. if so, the temps would sky rocket, fast. Been there, done that. MY ABF survived...

2. One can go ways sans water pump. Rely on thermo siphon alone.

3. The chances of an easy fix of the cooked engine are slim to none. Save the effort.

4. I cooked my XK engine. Zero in all holes!!!! I chose an LT1. but, way over four grand!!! I like it intense;ly. Plenty of HP, torque, mileage...

5. four grand might get a GM rebuilt crate engine. good value. New, not likely.. Then you need a lot more. Transmission. Munts radiator engne management, exhaust....

6. For budget reasons, A decent used XK. David Boger??

 

A professional charges around $20,000 to do a complete swap and get everything working properly.
Dumping a domestic V8 engine in isn’t that hard but getting everything working is massively complex.
That’s why it’s called lumping.

Buying a good used 4.2 is about the same cost as buying a used Domestic V8

Performance wise you are talking about a 4200 pound car. That’s a lot of weight to get moving so even with a lot more power it’s not going to be all that fast.

Finally service after a lump. Good luck. Most dealerships won’t touch it. Independents might do minor stuff but most won’t be bothered. It’s not about purity or anything snobbish it’s about practicality. They don’t have manuals, they won’t have parts, and training ehhhh!

 

Like Carl and Dave, I have the lt1, and after going through motor and transmission, I am way over 4 k as well, do I love it?? Hell yes! But as stated above, it’s not a cheap or quick endeavor! My vote is also for another xk motor to get you running again ( if yours is indeed toast, but even there, I think more digging needs to be done)

whatever it is you decide to do, we are all here to help you along!!!

 

Best engine swaps for an XJ6? Another XK6, a V12 or an AJ16, in that order.