Harry's V12 XJ Coupe - new engine issue

It seems a shame that Harry’s fresh engine needs work already.
What do you think?


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Looks to me like Ole Mobeks kit is much simpler, more complete, and easier to install than that contraption Tom Lenthall is installing.


The basic system that Harry fitted to his car has in its basic form has been fitted to V12s since 1975/6 - sure a few issues but basically still works.

I think Harry has been sold a pup with this new system - sure it will work but at a cost of over £20,000 I think the mechanic is pushing his own system. Any half decent V12 mechanic would have been able to sort the old system for very much less cost.

Harry seems locked into this guy, maybe he also needs to look elsewhere.


I think it should have been presented not as a remedy but as an upgrade/modification.
Like this he seemed silly and being sold to a completely unnecessary expense.
And even worse if you think that it wasn’t an issue with the intake manifold to begin with, as it had new injectors and all… it was either the ECU, or its wiring, or ignition related.
And many stand alone systems to choose from at a fraction of the cost.

Otherwise it’s not a bad modification if you have £20.000 to burn on top of the £70.000 you’ve put in already, or if you want to make a show on YouTube…
I liked the distributorless ignition though.

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Yes, that is nice, and the two Ford V6 coil packs are what the 6l x305 is equipped with by Jaguar.


I really like the distributorless ignition too! But for half the price, mobek gives you all that plus a real wiring harness, plus new injectors, plus AAV delete.

It is so tempting…


Completely unnecessary in my opinion. For the requested outcome of a nice running car, the original system is fine and can be sorted with minimal additional effort and cost to what he’s already done.

The fact that the car was dropping cylinders at temp, is a pretty good indication that something is up with the re-opus, or the ECU communication from a bunk sensor or short.

The car (I believe) was pretty rock solid reliable prior to the rebuild / they had a bunch of new harnesses made, etc., during the rebuild. Very easy to ground source and diag those early systems.

Watching them gut and replace with an entirely new system, that requires dyno tuning and maps, is brutal for a more or less stock car.

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It feels like drama created for the internet and to sell stuff.


Drama sells. HDTV is largely scripted. That program Love it or list it is essentially fake. The majority of houses that they visit are not for sale, and in most cases they have already decided which house they want.
You make money on uTube based on clicks and subscriptions. The more drama, the more clicks. In this case the increased traffic might very well pay for a system that is really not needed, but it builds his followers which is the prime objective.



Sounds great!


This is probably a dumb question and perhaps it was answered in the video, just did not see it.
What is the 350hp they quote - is that at the wheels or have they done some funny calc for losses to get an estimated figure at the engine? Would be good to know the atw Horsepower

I can’t imagine it is at the wheels. Since it is a manual car it is easy to measure drag when the engine is coasting. This is added and then a normalized power at DIN conditions (air pressure and temperature) is calculated.
At least that is the way it is usually done

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I have tried to find the answer to what gearbox Harry has in his XJC. I have been through the videos etc but what gearbox is in there does not seem to be mentioned.

I assume it is a Getrag 5 speed as fitted to other Jags rather than a T5/Tremec kit but I dont know.

Does anyone know what box is fitted?



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I guess no one knows :thinking:

I have been contact with Harry - it is a Tremec.

I was too slow- you can clearly see the box is a T5 type when it’s out of the car in the ? third video

Based on the dyno setup, it most definitely looks to be wheel hp vs. crank, unless they’ve grossed up the wheel numbers.

Achieving those numbers, at the wheels, is definitely possible, however with just stock internals, bigger intakes, exhaust and FI, its not likely.

Chances are they have reported the wheel
Hp with a correction factor around 20%, which would put actual wheel hp more like 280, which is still very strong and likely inflated.

Every dyno reads differently / I’ve had massive swings in numbers, and on boosted cars, they can be laughably high.

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I’m a little late to comment on this thread, but I am a little surprised by the fact that Harry didn’t do a simple upgrade to the fuel rail for the later version to deal with any vapour lock and/ or fuel delivery issues.
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He’s obviously not concerned about originality so why would he not want to make this V-12 perform at it’s optimum capabilities.

I actually wrote an email to the guy at the shop that did the EFI upgrade and he told me the dyno numbers were taken at the wheels but then they get “adjusted” to be crank HP & torque figures. This is not the way dyno figures are done here in the US and I always have my doubts about any magical “adjustment” of dyno output figures to go from wheel to crank approximations. When I suggested that this “adjustment” they made to get crank HP was a bit of a fudge factor the guy who replied to my email got slightly offended. :slight_smile:

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Oh my… that’s not how it’s done in any country :stuck_out_tongue_winking_eye:.

Good on you for inquiring, and they should redact that portion of the show, as the common grossing up percentage is 18-25% due to driveline loss, but it’s always been a meaningless swag.

Post the real WHP, uncorrected, and own it. If it appeared the real numbers showed a bill of goods to Harry, then they could have just done a back to back with a stock injected car (didn’t even need to be a coupe obviously), where the numbers would be stronger (hopefully :grin:).

Booo… :wink: