XJ6 & XJ12 Series I, II & III 1968-1992

engine mods ?

 
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Old 01-23-2012, 12:32 AM
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Default engine mods ?

What engine mods do you guys think i should do to my 1982 xj6 i want to pick up its performance if anyone knows anything or has any good ideas please share

thank u
 
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Old 01-30-2012, 11:16 PM
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Default engine mods ?

Originally Posted by sergez View Post
What engine mods do you guys think i should do to my 1982 xj6 i want to pick up its performance if anyone knows anything or has any good ideas please share

thank u
The delightful XK engine was designed for racing, but over the years emissions regulations and being installed in a heavy luxury vehicle have taken their toll.

The XJ6 Series III is a luxury car and is best used for relaxed touring through the countryside. The suspension is supple, but not harsh and the braking is more than adequate for a vehicle with the performance potential of the XJ6. Winning races in the 'stop-light' grand prix is not what this car is designed for, but a top speed well north of 100 mph is easily attainable.

Your best bet is to ensure all maintenance items are taken care of and the stake-down kit is installed in the head so the tappets don't work free with pieces finding their way into the timing chain housing.

NBCat
 
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Old 01-31-2012, 07:46 AM
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The "stately" acceleration of the Ser III XJ6s is a bit of a downside. But, to rephrase what NBcat said, "it is what it is" :-)

If you're flush with cash you can go to the AJ6 Engineering website and select from a variety of performance enhancers. The stuff they sell works.

Going to a 4-speed automatic and different (lower) differential gearing would help you make the most of the power you DO have. But, again, it's gonna get a little expensive.

I've had good luck by advancing the camshaft timing on the 4.2 engines. It'll give you a bit more pep. It's an old trick.

Cheers
DD
 
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Old 01-31-2012, 02:36 PM
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"Hotting up" Series 1 and 2 is probably easier than a Series 3, because they use carburettors, and the Series 3 uses a now obsolete EFI system. However the Series 3 has the big valves the Le Mans cars of the 50s had. Difficult really, as most commercial engine modders have long since forgotten about these engines, so there is not much stuff around now; the world has moved on.
 
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Old 01-31-2012, 03:54 PM
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Hey, if you really push it, you can give a Honda Insight or minivan a run for its money!
 
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Old 02-03-2012, 09:27 AM
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Fraser,

Based on your comments, then is the way to get more power to dump the stock efi and associated intake and mount carbs to the engine. Or another route to install an aftermarket efi setup such as Megasquirt? Could you use the stock series 3 intake (or the modified one by AJ6 Engineering) with a Megasquirt system or would you need an all new intake system?

Eric
 
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Old 02-03-2012, 04:45 PM
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Originally Posted by ronin View Post
Fraser,

Based on your comments, then is the way to get more power to dump the stock efi and associated intake and mount carbs to the engine. Or another route to install an aftermarket efi setup such as Megasquirt? Could you use the stock series 3 intake (or the modified one by AJ6 Engineering) with a Megasquirt system or would you need an all new intake system?

Eric

You would need a different intake for carbs and for me, it's a very attractive idea. I had an old VW Rabbit with a Scirocco 16v engine swapped into it running on twin side draft Dellortos (think Weber DCOE, same thing really) and I loved it. Had to pull the choke for 15 seconds when it was real cold out but otherwise a turn key operation. Our cars will never get respectable fuel mileage anyways, 3 40mm DCOEs sounds awfully intriguing. The music it would make alone would be worth it, never mind the throttle response and extra grunt that comes from having a throttle butterfly for every cylinder. Never checked but I would have to imagine there's still people out there selling sidedraft manifolds for the old XK. Not going to be cheap, though.

Megasquirt will come with plenty of it's own headaches and expenses. Don't even think about it if you're not comfortable diagnosing and understanding electronic engine management problems and principles. With MS you would retain the stock intake and may even be able to run the stock injectors and use many of the Jag's stock sensors. It's highly programmable, I believe you could, for example, program the resistance curve of the Jag Coolant Temp Sensor into it. You can use many GM and Ford sensors, too.

All that said it's my understanding of our XK engines that much of the real improvement to be had is in working the cylinder head. The peripheral stuff like bigger exhaust, higher flow intake, better fuel/air metering/mapping can only help to the point of the head's ability to get the air in and out of the combustion chamber. Either way you'll barely notice the difference unless you do something about that god awful 3 speed slushbox. It's the one thing I truly don't like about the car. Swapping in a 5 speed manual is pretty high on my list for that car. Interesting link on that topic. 1983 XJ6 5 Speed. To me there's no point searching for more power until you do something about the transmission first.
 

Last edited by vwtechnician; 02-03-2012 at 04:52 PM.
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Old 02-03-2012, 05:11 PM
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While we can all fondly remember the 'good-old-days' of carburettors and chokes, there is much more to that type of modification than just merely bolting on a manifold for three side-draught Webers. The camshafts have a different profile for both height and duration when using a carb setup, although one could possibly install the cams from a carburetted Series II XK cylinder head as a starting point and tinker with the main jet sizes and velocity stack lengths to come to some type of decent performance for a street-driven vehicle.

The XK is a beautiful design, well ahead of its time when invented back in the early 1940s as the initial intent was a world class racing engine. Many modifications are great for the track when the engine is driven consistently within a specific RPM range allowing the engineers to design inlet and exhaust systems that maximise both horsepower and torque. While higher horsepower looks impressive, most daily driving relies more on torque and the XK is a very 'torquey' engine with her long stroke, so I believe it would be in someone's best interest to clearly decide how the vehicle is going to be driven before ending up with something that runs extremely well at high RPM/high road speed, but is undrivable under normal everyday conditions.

NBCat
 
 
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