Im looking to swap my 86 xj6 over to a 350 instead id its 4.2 I6. The I6 already has about 165k miles on it and the engine has never been able to work for more than a week before something goes wrong on it. Im young and dont have money to pay for mechanics every time I want to use my car anymore so doing a 350 swap would be easier for me as I can work on that myself. I was wondering if anyone here has any experience in doing so and what to expect with it. Ive seen the conversion kits for sale as well and am considering to get one.

 

I have read some fourms on this already, but none have really gone into any detail.

 

It’s certainly doable, a few of us here have done it, and a few bought their cars already done! Be aware, it’s not a cheap ordeal, there’s also a lot of fiddle things to sort out, like getting all gauges working again, etc, are you thinking of going carbureted or fuel injected, you’ll see both here, carburetor is the simplest way, but it’s a bit of a backward step, you can do a search on my threads and read about my swap, there’s also lt1jaguar (Dave) he recently did same swap, good luck, people here will help you no matter which you decide great bunch of people here!

 

Thank you it’ll be much needed, and Most likely a carb due to the fact that I have always used carbureted vehicles and I just enjoy the simplicity of it. And expense is not too much if a concern, as I know a few buddies of mine who are good with wiring and general engine work as well as myself. The only real cost for me would be the kit and accessories as I pretty much already have a good engine for it.

 

Here's some reading; perhaps you've already visited, I dunno

Jaguar Specialties

https://www.johnscars.com/

What problems are you having with your 4.2 engine? Sometimes there are known, easy fixes. I'm not anti-V8 swap, but I'd hate to see someone go thru the effort, time, and expense of a V8 swap when easier alternatives might be out there.

OTOH, if you just have your heart set on a V8....nuthin' wrong with that, either :-)

Cheers
DD

 

Another option is JTR (Jags That Run). https://jagsthatrun.com/
Husband used these guys when stuffing a Gen 1 350 (which is what you're thinking about) into his 240Z so he, of course, thinks they're the Best.
(';')

 

I'm seeing a bit of a contradiction here, you don't have money to pay a mechanic, but you can do an engine swap yourself? I'm in the middle of doing a swap ( to the supercharged XJR engine) and I can tell you it's far more complicated, expensive and time consuming than I ever though it would be, and I had access to cars that had been converted before and took all sorts of photos and was told what the trouble spots were.

If you want it do it for the sake of doing it, that's fine, but expect it to not be quick, simple or cheap.

Another consideration is when you're done you've created an one off orphan that few mechanics will want to work on. A Chevy shop isn't going to touch a Jaguar, and a Jaguar shop knows nothing about Chevys. Which wiring colour codes are you going to use? Jaguar or GM? Where will you cross over, and are you going to draw your own wiring diagram for the car? If you don't, then only you can start tracking wires when something doesn't work. In many ways an engine swap forces you to be your own mechanic because you have created something unique. Unless of course, you have your own mechanic who will do the swap and maintain it, but that's not in the "I have no money" story

There is nothing particularly difficult about the 4.2, if you have sufficient mechanical skills to do a swap, then you have plenty of skills to maintain the 4.2. All the knowledge and help you could want is here.

 

You don't say how young, but when I was younger, (in the late 80s), I removed the engine and gearbox of my 1980 XJ6 and stripped the engine right down to a bare block then rebuilt around a replacement block which had no cracking. Either way you go, (rebuild the Jag engine, or insert a GM "lump"), is going to cost you money. I would expect an 86 engine to be basically OK, but with that mileage, almost definitely in need of an overhaul. It's not a particularly difficult job to do but you do need the facilities of course.

 

+1 on refurbishing the XK engine already in the vehicle as the best and least expensive method to make the car reliable.

Where is the vehicle located? Find a Jaguar specialist who know what they're doing instead of creating a lump no one wants to touch.

 

Logan,
Read my thread, if you haven't already. It will bring up some of the issues that need to be solved doing a Chevy lump. There were many more that didn't get posted.

There is about a 60/40 split in advise to fix your existing 4.2 or do a 350 swap. Jagboi64 posted a good set of issues/questions you will need to consider when doing the swap. But it was just the short-list of the many, many things that will need to be addressed. To do yourself proud in a swap, you need time, money, skill, a dedicated place to work, and most importantly, the long term commitment to see it to the end and make it a reliable car, better than what you have.

The other side is suggesting to figure out what are the issues with the 4.2 and correct them. Fraser's point of a complete overhaul would be the obvious route for me, given the high mileage. "Rings/bearings/valve job" might do the trick, provided everything else still had life left. This path would, of coarse, solve all the interconnect problems of a swap.
I don't know anything about rebuilding the Jag XK engine in particular, but there are many very excellent members on the Forum who do and would be willing to give any help you might need. There are also many knowledgeable members who are willing to give you any help you'll need if you decide to "lump".

I made a specific and committed decision nearly 4 years ago to build another car, one that I would put a different engine in. I didn't plan for a Jaguar, but the one I found fit the bill and I liked the look. I have a shop, truck-load of tools, unlimited time, and allotted a certain amount of $$$$. But most importantly, I really wanted to do this build (swap included) and my commitment saw me to the end. If you start and then stop anywhere short of completion, everything becomes a waste and you have a completely disabled car.

Anyway, that's my two cents worth based on my experiences with lumping.

Dave

https://www.jaguarforums.com/forum/x...j6-lt1-211881/

 

I will echo Dave's comments above. Even with a dedicated facility, tools, knowledge, and a crate full of pre-fabricated parts ready to go and paid for, it's still a challenge to get a project done. You will inevitably run into technical challenges that will incur additional cost and labor (read: downtime).

My past projects (a handful of LS engines into foreign cars) always started with a few questions:

-Why am I doing this, and what are my goals?
-Perhaps reliability, but know that upon swapping a car you become its "caretaker", as you will be the only one that knows the ins and outs such as wiring and plumbing details unless you thoroughly document that.

-Is it in my budget and allotted timetable?
-Also examine your current skillset. If you can't repair the existing Jag motor due to either lack of finances or knowledge, it may not be as easy to swap the Chevy motor as you think.

-How I am getting around while this car is down?
-When I swapped my BMW 540i 10 years ago the first thing I did was buy a reliable daily driver (cheap Subaru Outback).

-What else needs to be swapped to support the new drivetrain?
-Significant costs can be expected from the various engine mounts and hardware, engine management, wiring harness, fuel system, cooling system, exhaust fabrication, driveshaft, shifter etc...everyone always think it's dirt cheap to swap in a Chevy motor because "they're only a few hundred bucks at a wrecking yard". Also consider any costs associated with refreshing your new powerplant/transmission.

The worst thing you can do is jump in without a plan and start dumping money into the project without understanding the true scope of work. That is how projects end up sitting on jackstands for years or rotting in backyards.

 

My swap bewgan in 2001. It passed CA SMOg in 2006. I was working then, time to work on the car was on week ends.

I hve twisted a lot of wrnches. Including buiding a 50 Hot rod from scratch. and rebyikdig ghe IL6 in my FJ40. Twice!!!

The jaguar swap was the most chalenging. WFI, Never before!\\There were aboput 5 outfits to deal with as to a kit. I chose Johnscars in the Fworth Texaas area. Most complete. Not cheap either. I vought a harness. Mistake. should have modified the existing GM harness.

Ging carb makes it simper. Swap in a fuel pump as the Efi delivers too much PSI. Add a regulator, Not sure as to tht one.

Guages not comlex Use Haf sensors in the Gm. Tach and speedo a bit more complex.
Basics. Engine mounts. Transmission mounts. Gm radiator. Jag radiator not enough.

Then exhaust. .

Most Gm maniflds will not clear the steering tower, GN Rm hornbs are the usual fix.

The muffler shop will want about a grand to do a god job.

but they sure do run ne.I recall my frst trip around the block. Open manifolds. No bonnett!!!

Carl

 

I agree that rebuilding it would be easier, however that being said, finding parts for them is insanely difficult and expensive. And the vehicle is in IL, I have contacted a few jaguar dealerships and a specialist. Most of them said they dont even have anyone who would know where to begin with a car this old. And the ones that do charge 230 bucks and hour. And overall, the XK engine is just plagued with problems since it was made and although an engine swap would be costly, itd save me a lot of money in the long run as I can work on a 350 motor myself. I had the car at a mechanic for 6 weeks and even after that they still couldn’t get it, and ive been going to these guys for years and have yet to be let down.

 

Not set entirely on a V8 swap, just in general it makes more sense for me. The engine is currently not getting fuel, at first there was no fuel pulse. I tracked down the wiring and found it all to be okay. Then determined in might be a computer. Got one and after that still nothing, after chasing the problem for days ive come up short. New ignition switch, injector, and wiring have not fixed the issue. And just generally this engine has always been a problem. It needs every single seal to be replaced as it leaks everywhere, it sounds like there may be a rod knock on cylinder 5 when it was running, I also need all new sensors and wiring as it is just a complete nightmare. I would have to do a total engine rebuild, with every hose and wire apart of that, and hope that it would solve the issue, and generally the XK engine can be reliable, but it always will breakdown at some point, where as a small block chevy is usually durbale and hassle free as long as it has been maintained. But time will tell. That is why I came here looking for advice

 

Thank you this actually helps alot!

 

Yes I have considered alot of this as well and you make a great point. My main reason for a swap would be reliability and repair ability. Jaguar engines in general are not reliable and parts are hard to come by. Chevy motors are reliable and simple, as there arent many sensors or wires in general, and everything is easy to access. Changing the battery cable alone took over an hour whereas in a chevy its a 2 minute job. I also have a couple friends who have done engine swaps before and they are good with electrical work and such so it wouldnt be me alone on it.

 

I will definitely give your thread a look and see what you have written there. This particular jagaur has been in my family since I was born. It actaully is what started my love for classic cars (Ive been daily driving a 64 buick electra since I was 15) and have no intention on giving up on the car, as if I did it would have been long ago. My main concern with the current engine is that I am a novice with most work on efi cars. I can work on a carbureted V8 all day as I have for many years. The current engine has always been a hassle since my grandmother got it many years ago. Most if not all the wiring under the hood would need replacing, as well as every hose, and every gasket. I really would like to enjoy the car and use it, and I just don’t see that being entirely possible with the current XK engine. I have much more experience with american V8s and this heavy of a car could use a little more torque than the 4.2 offers anyway. I havent entirely ruled out a rebuild, but a chevy motor seems to make more sense for me and I have a few buddies who are skilled with engine swaps who do know what to do for the most part. My one friend completely restored a 85 Blazer and put a Ls2 motor in it and it runs like a dream.

 

You make many valid points and I appreciate your advice greatly. This issue I have currently is that no mechanic in general wants to touch this car and even a couple jagaur dealerships said they have no clue on what to do with it. I have a lot of experience with carbureted american v8s, and a few buddies of mine have done engine swaps on their cars and they are generally very good with EFI systems and electrical work in general. All of which said they would help me and teach me along the way with that stuff. I like the idea of an engine swap because this 4.2 is on its last leg and would need a complete rebuild along with a complete electrical teardown. I have alot of experience with 350 motors so if something were to go wrong, I could fix it in a day versus waiting weeks for parts to show up and hoping I found the right problem. On the other hand this fourm has given me alot of encouragement to want to learn more about the 4.2 so perhaps I may just drive into it. Much appreciated!

 

Don't forget that reliability is the entire system, not just the engine. As you are seeing , it's typically not the engine itself that is the problem, but all the supporting things - fuel, ignition and cooling. You would have to do a swap to a very high standard to get close to the reliability of a factory system. Simply changing to a 350 without everything else being properly done isn't a guarantee of increased reliability. As an anecdote, I used to have the V12 version of the car you have. It uses a GM ignition module ( as does your car, it's an HEI ignition system), GM AC compressor, GM transmission (TH400) and GM power steering pump. Every single GM component failed on my car, while the Jaguar engine kept on going, so in my experience "General Motors" and "Reliability" are not words that naturally go together.

You talked about changing the wiring under the hood (why? Is it really that bad?) and hoses, but if you do a swap you're forced to do all that anyway plus a lot more wiring and plumbing to convert the fuel system from EFI back to a carb system. If you're really serious about going to a Chevy engine, going to TBI would be easier as all you would have to change is to a low pressure GM pump.

Parts for the XK engine are easy to get, you can get plenty on Rockauto, or any of the Jaguar specialists, either in the US or UK. I generally order my parts from the UK and they come DHL in 2 days.

I understand that you're comfortable with GM engines, but consider than it might be an easier path to learn the Jaguar and keep it as it was built. All the knowledge and guidance is here and there are plenty of members who will guide you in diagnosing and repair. The engine and EFI is actually very simple, I think much simpler than tuning an American carb - changing metering rods, jets and power valves? Ugh, no thanks, what a nightmare.

I have seen many swaps that kind of, sort of, work but very few that actually have everything work, like the gauges, cruise control or air conditioning. For example, can you calculate driveline angles in multiple planes and fabricate engine and transmission mounts that support the engine at the correct angle relative to the differential? You'll need to, to do a swap that doesn't tear out U joints on the highway.

As was mentioned by another poster, you must have sufficient resources to see it through, including skill, time, money and workspace. If any one of them run out before you're done, then you have a shell that you've sunk a lot into and may end of having to pay to get it taken away.

 

Yes there would definitely be some things to work out no doubt. And when it comes to the conidition of the electrical work, yes every wire is crunchy and spliced. 90% of the sensors and relays need to be replaced or redone. Which is odd because the body and interior is in very good condition. I know at this moment, I would need new transmission mounts for the XK. Entire new fuel system, ignition system, all new electrical work. The starter needs to be either rebuilt or replaced. A full engine rebuild will be needed as the piston rings dont seal right and the oil turns to almost 70% gas after a few hours of driving. In general the 350 I have in mind would be a almost 100% mechanical. Mechanical distributor cap, mechanical fan, belt drive ac pump and everything. Cruise control is no concern as it would cost way too much to fix (ive had it looked at before). But yes there are many things to consider which is why this forum has been very helpful