Yesterday the mechanic working on my 1991 xjs, v-12 stated the cost to overhaul my engine would be between $15,000-18,000. His initial estimate was $8,500. He said everything would have to be replaced, engine bored, new harnesses, etc. the list was massive. What I fail to do, and kicking myself…not hard enough I might say, was to have him give me a list of what the initial overhaul would entail. His initial price seemed in line with what an engine overhaul might cost for an xjs. Yesterday,at least I had the sense to ask for a list of the new things he’d have to do which he said he’d provide ( obviously different than his cost sheet ) I know it’s impossible to say what the cost of such an overhaul might entail, but I need an objective opinion, aside from the mechanic. In other words what sort of engine work might warrant such cost. No miracles expected here, just educate guesses.
What’s broken in your existing engine such that you need a full rebuild? A drop in replacement with a known good donor engine would be the most economical move.
Needing a new harness isn’t surprising given the age of these cars and heat effects on them. I don’t know how he’s planning on sourcing one. I know folks are having them built in the $400 range.
What surprises me is that he’s suggesting the engine needs to be bored rather than just honed. That’s plausible, but often these V12’s have so little wear that they cylinders can be honed & any ridge removed. Boring usually = need for oversized pistons & that added costs. Once you’re there (cost of Jaguar Pistons) it might begin to get worth looking at custom machine + custom rods to increase the engine’s displacement (there’s the cost of tuning & ECU changes to consider)…
Near $20K is a price not unheard of at some of the Jag specialty shops. But I’ve seen DIY rebuilds for the very low thousands.
It’s quickly cheaper to source a junkyard V12 engine.
Here’s a very non-exhaustive list just based on searching costs:
Gaskets:
Upper Gasket Set $270
Bottom Gasket Set $60
Misc Gaskets $100
V12 Bearing:
Mains: $130
Conrod Bearings: $170
V12 Timing Chain $40 ->$300
Dampers: $45 + $85
Tensioner $300
Rings: $145
Oversize Jaguar Pistons?!? NLA I’ve Heard. $2000 TeamCJ set.
EFI Harness $500?
Machine Shop Costs:
Headwork:
Cleaning: $70
Skimming: $150
3 Angle Valve Job $500->1000
Seats? 12 X $25 + seat cost & machining
Guides? 24 X $5 to $10 + Guide Cost
Block:
Cylinder Resize: $500? (means new pistons needed).
Just Hone Cylinders $200
True-ing/Decking?
Align Honing?
Head Assembly? HOURS & HOURS!
Engine Assembly? Hours
Boring/Stroking = Very cooperative mechanic or DIY
Custom Rods $2000 + Ford sized Bearings + Machine Shop Work on the Crank
Custom Pistons $1500 + Rings
ECU Retune: $500 - AJ6
6.0 to 6.7L depending on bore/stroke changes.
A lot is being left out of guesstimates above… . Labor. Additional machine work Lots of misc items… Machine cost vary.
Best of luck
~Paul K
Or lumping it if you didn’t feel the “need” for the v12. I’m half tempted to try to figure out how to put in my spare xk8 engine if my 6 goes out. At least it would still be a Jag engine 
What you have been given is a ”guesstimate” of the costs to rebuild your engine.
You are entitled to an “estimate” for this work…this should include a breakdown of the parts involved with costs …and labour estimates for the work involved with costs.
If the mechanic provides you this it means that they have researched what is required and you should not get any major surprises. If you accept a wide range “guesstimate” you will be charged what the mechanic thinks can be extracted from you…this will surprise you!!!
It is fair enough to provide an initial guesstimate to set an order of magnitude…but important to get a detailed estimate for the reasons above…and it also provides a basis for deciding if the offer is reasonable and should be accepted or declined.
Chaz, I don’t believe this guy knows what he is doing. There are no oversize pistons available, if the liners are that badly worn then you have to replace the liners and pistons.
I don’t know how many miles your engine has done, but I’m just rebuilding one due to a dropped valve that has done only 139K and all I had to do was deglaze the bore and fit new rings.
There was no measurable bearing wear so the bearings were reused, valve were reseated and new valve springs were used due to the overheat.
As you can see, parts cost was minimal, but labour including R&R was about 70 hours.
For that kind of money some of us probably would sell you our low milers and you will be just as happy
That fact was what tipped me off that this mechanic may not understand these engines.
i just do not understand some mechanics and there pricing!
it is just a simple two valve ,single overhead cam engine, just more cylinders, as far as engines go its antique engineering!
its the JAGUAR name that puts the price out of space!
sure wish i was younger , i’d jump on that in a heart beat!
ron
ron
I guess we first need to know what happened to put your car in the shop and why the engine needs rebuilding. Maybe it does not need a total rebuild.
I have rebuilt 3 V12s although it is not my regular occupation. None of the engines had serious wear and tear due to normal use. The last one had badly corroded heads due to POs never adding inhibitor.
One liner and piston had a few dings due to the PO dropping a screw into the manifold.
A set of brand new heads was reasonably priced, and very easy to get a 2nd hand liner and piston.
From there on just a normal rebuild. All the other liners were honed but they had close to zero ridge in the bores. Unless they are thrashed or poorly maintained the engines will do a lot of miles before needing a rebuild.
I think Norm Lutz’s report of 70 hours plus parts would be about right. However, if other things need fixing at the same time costs will escalate.
As suggested already, a 2nd hand engine in good running order might be reasonably priced, say US$2k - 3k. On top of that money for taking out the old engine and putting the new one in plus bits and pieces. Maybe US$5k - 6k all up.
Unless the general condition of your car is spectacular might be better buying another car which does have a running engine.
I thought about asking him to look into another engine possibly, but one never knows how much wear and tear an older engine has. He thinks it best to do the rebuild even with the cost because he says he’ll use the best parts and at least I’ll know it was done right. Obviously there some validity to is statement.
Thanks…Much appreciated
Car is in good shape. Just spent $4000 on differential. I’m heavily invested. If the value rises in value, maybe worth it, juxtapose to a car decreasing in value.
Thanks
That thought crossed my mind but just got the bad news yesterday.
Thanks
That just seems so expensive to me.
I would expect him to remove engine and polish all the bits for that price.
Would love to see photos of your car and engine please share.
Mine even asked for 21K for a total rebuild and his list was also excessive 
(V12 carb) … I did it by myself with parts @2k
The worst that can be is that the crankshaft is heavily worn (i heard it is very unlikely). Even with new pistons and liners it can’t be that expensive and the job is easy. Investing 18K for this won’t increase the value of your car more than investing 5K. You can have most parts new (valves, pistons, liners, bearings, chain …) at reasonable prices.
Sorry Chaz, but anyone that charges $4K for a diff rebuild is not lookong after you.
A $4k bill for a diff is mighty steep.
If the whole back cage, diff, brake and suspension parts including anything and everything was replaced, then you might nudge $4k. For all that being needed the car would have to be very high mileage or a bit knocked about.
Still be interesting to know why the car is in a shop with a suggestion the engine needs a rebuild.
Yes, As I recall, there were other considerations, not just the differential alone. Don’t recall off hand what they were but, it was something when presented, I felt it was necessary.
Thanks for your input. You jogged my memory. I had a moment when I thought the people I trusted screwed me, but after you jogged my memory, there was other factors.
Richard, I had numerous oil leaks, an output exhaust pipe that burned through and was impossible to repair due to its condition. I had two mechanics look at the oil leaks and given their severity felt that the cost for just these two items would be extensive, plus one of my valves was noisy. But the big reason was I’d had work done five years ago, only to find it was a god awful terrible job. The mechanic had his helper pull the head and the aftermath wasn’t pretty, even costing me and additional $5000 because the wires on the passenger side shorted and had to be replaced, a few weeks after the work on the head. I was relocating to another city, things were hectic and didn’t think I had enough evidence or knowledge to pursue a claim. Once the engine came out it was a mess, not only from that episode, but from years of bad serving and sloppy repair prior to my owning it. There are people who have cars like this but don’t have the money to keep them up to speed. I’ve had it for 20 years and always felt it wasn’t a 100% right, aside from numerous costly repairs.Once the entire engine was revealed, it was obvious why. The entire engine had to be pulled to see the numerous issues, ergo the rebuild which is now obviously much worse than a customary rebuild. There you have it. There were moments I thought there were few things left to replace.LOL
Obviously you, unlike me, have mechanical skills. I also have several physical limitations that would not permit me to undertake such a project.