Hello, I bought and 89 XJS with the 5.3 V12. For a number of reasons I am considering replacing the engine with something else ie 350. I know it’s happened before, wondering if anyone has any suggestions on things I should consider, best options for the new “heart” and where I might consider having the work done. I am located just outside of Toronto, Ontario. Thanks!!

 

I'll be looking forward to seeing where this one goes!

 

Here's one place to begin reading:

Jaguar Specialties

Others here have been there and done that with V8 conversions and will offer loads of input.

Cheers
DD

 

it’s not easy. Professionals charge $20,000 to do it. Usually there is a lot more needed than just the engine. The number one problem with Jaguars of that era is wiring. It’s a nightmare. Then the rubber fuel lines and vacuum lines. Followed by HVAC issues,
More than 90% of the time the engine is in fine shape. It’s amazingly well built. The Crankshaft for example is a forging (EN40 steel) while most Chevy’s are castings. Chevy rod throws are 2.100 while Jaguar is 2.300 with a much shorter throw. Jaguar has longer rods than Chevy, big beefy forgings again of EN 40 steel! And the going price at junkyards for a guaranteed engine V12 is $500-1000.
Finally people confused the way the power is rated. For example Chevy’s 350 rated the same way the Jaguar is rated is only 160 hp. Compared to Jaguar’s 262 hp. In fact the Chevy 454 is rated at 230hp compared to V12’s 262 hp.*
If you want more power in your V12 Isky will regrind your camshafts to give you an extra 100 hp for $300 It will take you twice as long to replace one Chevy camshaft as it does to replace both Jaguar camshafts.
If the Fuel injection scares you. ( it looks complicated ) swap for an early 4 carb manifold from a 1971-1974 Jaguar V12. Those 4 carbs are bigger than a Holley Dominator and are lawnmower simple.
Plus there is a manifold out there that has 2 Holley 4 barrels. That bolts on the V12. Or if you really want to get sexy use Webers.
There are simple things you can do that will add 80 horsepower. On any V12.
Oh and Jaguar uses inch not metric on all the bolts.
Finally if you like the idea of turbo’s the Jaguar can add as much power as any comparable sized engine. You’ll just have to be clever enough to figure it out. (Hint, Megasquirt Gold)
* A big part of why the Jaguar doesn’t feel as powerful as it is is because it’s tuned for fuel mileage, smog, and top speed. Stone stock a Jaguar XJS will do 150 mph. While most Chevy’s are closer to 120 mph.
Another part of why the Jaguar feels slower is because the car itself weighs 4600 pounds. Most of it is luxury. The front and rear suspension are isolated from the car in their own rubber isolated crossmembers. With sound deadening and heat shields that Chevy doesn’t have.
If you like sporty. Swap that GM turbo 400 automatic transmission for a Chevy 5 or 6 speed manual it’s a simple bolt on once you make a home made adaptor
It takes about a morning to do. Ask I’ll walk you through it, nothing more than a drill press and some way to cut aluminum.

 

Can you give us some reasons why your are considering an engine swap? Has something failed, was the car a fire damage insurance write off and it needs a new engine, you want more power, or??? Knowing the "why" we might be better able to guide you and offer suggestions.

 

Hello Jseaman

Depends on what your end goals are - below photo's are from Doug a little while ago

Old school transplant

New school transplant.

There are a lot of forum threads about transplant - just go in the advanced search function and type in transplant, or 350 (in the XJS/X27 forum) and read up. Some are very successful, some end in heart ache.
Lots of opinions, Example below
https://www.jaguarforums.com/forum/x...s-swap-231308/

I quite like the old school transplant, as you lift the bonnet on the side of the road and get it going again.

Depending on what is wrong with your motor, there is a place in the state we live that reconditions V12 - for approx 11k, there might be a similar rebuild place near where you live.
My advice - take the time and read up, plan, make a budget (and times by 2 at least) and go for it

Cheers
Steve

 

You make a good case for a Transplant. Perhaps you neglected to mention the economics of transplanting Jaguars? Those XKE’s are now all having their transplants reversed in order to capture the resale of originality.
If you’ve noticed the market price of Nice Jaguar XJS’s has steadily gained to the point where prime examples are approaching or has past their original cost.
However I understand some people don’t care about money. So, yes you are free to do as you wish.

 

Thanks for responding. The issue is really about ongoing support and maintenance. Not that concerned about power rating. I just want to know that when i reached the extent of my own limits I can call someone who can help

 

if you’re willing to do the work this site is filled with great generous people who will help you through your problem.
I am not really one of those. I’m a racer and 99% of what gives problems I’ve removed or replaced with alternatives.
There are some things I can help you with. For example the simplest way to find out if all 12 cylinders are firing is to buy a cheap ($25) infrared temperature detector. With the engine warmed up Point it at each cast iron port of the exhaust manifold. If they are all similar temp. You’re good! If one is cooler. Decide if it’s spark or fuel. I have a cheap ($20) pen that I set on the plug wire and if it glows periodically the problem is likely that fuel injector.
If someone tells you something bad is going on in your engine buy a cheap ($50) bore scope and after removing each spark plug stick it in and look. After looking at all twelve you’ll know if there is something wrong inside your engine.
Those simple fast test will save you a lot of money. Knowledge is power. It’s fear that often causes us to waste money doing needless repairs.

 

Is there not a Jaguar specialist in the GTA? I've bought a car from Birkshire Auto in Thornhill and was happy with them. They also have a service side, but I also realize it is a long way from Mississauga.

Part of the problem with a transplant is that everything is custom and unique to that vehicle. Wiring especially can become a problem, as there are things that new wiring needs to be created. It will come down to how well it is documented, and if a proper wiring diagram is developed that someone else could follow and troubleshoot down the line. The cars are old enough now that every problem that will develop has developed and the collective wisdom here can narrow it down fairly quickly. Even if you don't do the work itself, you can have a knowledgeable conversation with a shop that will do that work.

If, however, you've had another engine transplanted (no matter what it is) then none of us can say what was done or how without being there looking at the car. In a sense the car actually becomes less serviceable and more expensive to maintain because a mechanic will have to start from scratch every time and start tracing wires because the car has become a one off. When it's non-factory you would need a complete list of all the part numbers that were used on the conversion and keep a master list, as no-one will be able to search by application anymore.

If you do have problems with the car, do you know it's a component, or a problem with the conversion itself? To give an example, I have a 1966 S Type that has a Ford Mustang 5 speed transmission fitted. I have been chasing vibrations for the longest time and it turns out that the driveshaft angles across the driveshaft universal joints was incorrect and that was what was causing the vibrations. It was a result of doing the conversion, rather than keeping things original created the problem. To fix it I needed to have (another) custom driveshaft made and also get a machine shop to custom make a transmission joke that a CV type joint could be fitted to. It was lots of extra work that was created by the conversion.

If keeping your car serviceable by others is your objective, then I'd strongly encourage you to keep the car original. Making modifications introduces so many unknowns before any problem can even begin to be diagnosed

 

You’ve hit the real nail on the head. Take your Jaguar to the Chevy dealer he won’t want to work on it. Same with the Jaguar dealer. It doesn’t have anything to do with originality. Rather business.
Even with a complete set of new wiring diagrams, part numbers and the most basic components, without training and prior experience nobody can tell you what it’s going to cost. In effect you are opening up your banking account and telling them to take what they would like.

 

I put a lt1 with the 4l60 trans in my '89 xjs 21 years ago. It's been virtually trouble free for 50k miles. It wasn't that big of deal to me because I have the mechanical ability. If you can't do it yourself, I would not recommend having someone else do it. $$$$. However, the end result still puts that ear to ear grin every time I drive it. When I bought the car, the engine was already gone so it was just a roller. Your average '89 coupe body. Alot goes into it to make it complete.

 

If I was in a situation where I HAD to replace my V12, I'd call Jaguar Specialties then bite the bullet and get this. 430HP, 6 speed transmission, wiring harness and all the engine/transmission bits you need. It's not cheap but it's ready to go.

 

Well said. It is your car you can do as you wish. But accept the consequences if you do.
I’ve bought 20 new Chevy’s over my lifetime owned 4 used ones. Even built a Corvette race car.
My personal opinion is the Jaguar V12 engine is really tough and durable. It really takes a lot of neglect or ham fisted mechanics to hurt the engine.
The rest of the car isn’t so great. Wiring is terrible due primarily to labor issues. although a serious effort was made to design it well.
The HVAC is terrible. Radio? Nah!!!! Upholstery is really pretty great. Properly maintained its a wonderful quiet cruising machine capable of speeds up to 150 mph. That for what it is gets decent fuel mileage.
If you want to race stoplight to stoplight you will lose. American cars (Chevy’s) are better at that.
the Jaguar can change it spots. But it will then lose much of what makes it a great cruiser.

 

Want a high performance V8 just buy one - just sayin'

I have that - and an XJS - there isn't much staying with the XF if I choose hooligan mode and it is 100% more comfortable than the XJS.

Never understood the mentality that buys a car fully intending to chase HP and spend twice as much doing it as buying the HP in the first place - the XJS is as reliable as the maintenance and it needs a lot of it even if you replace its heart all its other quirks remain.

 

Sometimes a person doesn't have the free cash to afford the horsepower all at once. So they do it in stages, buying things as money allows, and they do it themselves. Neither way is the right way or the wrong way. It's just what the person can do at that place in time.

Jack

 

Well, not everything in the car hobby has to make perfect sense We'd all be driving Honda Accords rather than 20-30-40 year old Jags !

A lot of people love the Jaguar style and road manners....but want more power. I have no problem with that and, in fact, I personally think that's the most legitimate reason for a V8 swap. But other people have other motivations.

Yes, it easier and really makes good sense to just go out and buy a car that already has the level of performance you're after. But, mark my words, a lot of conversion guys will tell you how much they've enjoyed the process. And most conversions nowadays are very nicely executed and my hat's off to them for their dedication in doing a nice job. In the years past many were cobbled-together messes just to keep the car on the road. I think those days are pretty much gone.

A conversion is the right choice for some people, not everybody. Keeping a the Jag engine is the right choice for some people, not everybody.

I get a lot of satisfaction from running a V12 as a daily driver. I feel a sense of accomplishment and I enjoy the weirdness of it all. I enjoy telling people it has a V12 when they assume it's been converted. I'm sure that the lumpers we have nowadays here on JF have an appreciation for the route I've taken even though they went a down a different path.

Cheers
DD

 

Your car is beautiful! Nicely done!

 

Hmm. I would imagine that unless you were able to use the exact SAME guy that installed the new engine, another mechanic coming after (even finding one) might get pretty nervous about going into a job on an XJS with a custom engine set up - especially if it were a mysterious issue or something other than regular maintenance...

Is there more ah compelling reason why you think a custom engine set up would make life easier? I promise the intention isn't to criticize or second guess, I'm just wondering. It's such a big undertaking, and can be so so expensive, especially if you'd need to hire someone to take the job on.

 

Good point. The vast majority of mechanics and repair shops are not the least bit interested in working unique/rare/modified/unusual/hobby cars. There are a lot of good reasons for this.

Cheers
DD