Hey all,
I'm about to ensure my new cat can prowl for many years to come.
The head gasket is getting done, because it needs to, and anything else I find whilst it's off will get sorted.
I've asked on another thread about where to source parts, but whilst I'm going that far, as I'll machine both head and block to match, replace bolts, cylinders, bearings, whatever,
I may as well go a bit further..
I'm aware these had over 200bhp when new and laughed at the fact police cars didn't even bother trying if challenged, but with almost a quarter of a million kilometers, again, no point.
So, what should and also what could I do?
I'm getting new suspension, am happy to upgrade brakes, see no particular reason to not fit a supercharger (or turbo/s). Nor any particular reason to.
If the gearbox needs some love, then love will happen.
Whilst my budget isn't unlimited, I can do almost all of the work myself. Even the machining of the head and or block! (But because I'm not a complete idiot, I'll get a local company I trust to do it for me because they do it for a living. Yes I'm bloody good, but sometimes I'm also intelligent).
So what should I do?
Anything particular to look for?
And because this thread is about power, how can I get more?
Whilst top speed is important, I'm seriously wanting some serious punch. Full face, closed fist the size and texture of a cow at warp speed smack you back in the seat power!
Well maybe just it's hoof, not the whole cow.
So, if you could, just because you could, how would you make a cat purr like a kitten, roar like a lion and charge off the mark and keep on charging like a sex crazed rhinoceros on bad acid?
And if it could stop and do other fancy stuff like go around corners, that'd be grand.
Cheers
(Make that 2 hooves, maybe 3 plus a crack in the back of the nog by a tail .)

 

The usual 'hot rod' stuff applies: extractor exhaust manifolds/headers and low restriction mufflers, low restriction air intake, more aggressive cams. You might check AJ6 Engineering's web site to see if they still offer 4.2 go-fast items. They had a tricked-out intake manifold, modified ECU, and other goodies. Fifteen years ago the full package from them was about $2500-$3000 as I recall and yielded about 40 more horsepower. That's expensive for 40 horsepower but nobody else offers the same things.

Other companies offer more aggressive camshafts but those might not be the best idea for a 4000+ pound street driven sedan with tall gearing and an automatic transmission.

Speaking of which, a change of gearing and a modern 4-speed automatic would be a big help. You probably have 2.88 gears, maybe 3.07. Neither does anything to help move a heavy car off the line.

A larger front anti-roll bar and adding a rear anti-roll bar, and Koni or Bilstein shocks, would do wonders for cornering....but make sure all your other suspension bits are 100% up-to-snuff before spending money on upgrades.

That should be enough to get the conversation rolling.

Cheers
DD

 

Mate,
Your advice on using top quality upgrades is well noted. That's the reason I've done a separate thread asking people around the world about parts suppliers.
But, gearbox. Please extend
By go to a newer, you may mean a $5000 box new in it's own big box or you may mean current models, therefore adding a numeral to the prior figure.
Do you have any suggestions?
I've noticed when flooring the girl at the lights, in a straight line, on a 39 degree downward slope made of rubber coated marble with a category 5 cyclone providing tail wind, ice ages pass us. We catch them, pass them and salute rude gestures through the sunroof at their ever diminishing past existence, but I could probably drive home and get the yellow beast, polish it, fill it with bad intentions and question why I'd, or anyone'd, buy the most dangerous BMW in existence, then proceed at an ungodly pace to pass them, their unborn children, technology and Isaac Asimov before the old girl could do the same.
Now I'm not looking for 638bhp, but would realistically love to say sayonara to 207 and crack 300.
As for exhaust/intake etc, again, any suggestions?
And.
I'm not joking about a supercharger.
Ideally 2/79 seems appropriate, but I'm unsure if either that would work, fit or exist in reality.
Any thoughts?
I could just say bye bye jag and hello ls3, but I actually want to do that (with 5/71 and triples) to a white series 2.
Cmon, live vicariously, help me make the jungle itself give up and leave the world to the night cats!!!

 

Here in the 'States, at least, it is very popular to use GM 700R4 or 4L60 (early and late versions of the same box) behind Jag engines. These transmissions have a low first gear for much improved off-the-line oomph and an overdrive fourth gear for relaxed high speed engine RPM. This o'drive fourth gear allows going to (let's say) a 3.54 differential without the downsides. You're making best use of your available horsepower.

Last time I checked the conversion kit was about $1000. Used transmission maybe $150. Full overhaul of used transmission maybe $1000? Starter, flywheel, misc small bits, maybe another $500? Just tossing out some numbers; other might chime in with specifics.

I'm not sure how readily available a used 700R4/4L60 transmission would be in your neck of the woods


Cheers
DD

 

Mate,
Your advice on using top quality upgrades is well noted. That's the reason I've done a separate thread asking people around the world about parts suppliers.
But, gearbox. Please extend
By go to a newer, you may mean a $5000 box new in it's own big box or you may mean current models, therefore adding a numeral to the prior figure.
Do you have any suggestions?
I've noticed when flooring the girl at the lights, in a straight line, on a 39 degree downward slope made of rubber coated marble with a category 5 cyclone providing tail wind, ice ages pass us. We catch them, pass them and salute rude gestures through the sunroof at their ever diminishing past existence, but I could probably drive home and get the yellow beast, polish it, fill it with bad intentions and question why I'd, or anyone'd, buy the most dangerous BMW in existence, then proceed at an ungodly pace to pass them, their unborn children, technology and Isaac Asimov before the old girl could do the same.
Now I'm not looking for 638bhp, but would realistically love to say sayonara to 207 and crack 300.
As for exhaust/intake etc, again, any suggestions?
And.
I'm not joking about a supercharger.
Ideally 2/79 seems appropriate, but I'm unsure if either that would work, fit or exist in reality.
Any thoughts?
I could just say bye bye jag and hello ls3, but I actually want to do that (with 5/71 and triples) to a white series 2.
Cmon, live vicariously, help me make the jungle itself give up and leave the world to the night cats!!!

 

Wringing 300 horsepower out of the old 4.2 is a tall order.

I'm sure it is technically possible to reach 300 if you were building a high-RPM engine for track use.

Or, yes, a supercharger, as you say. But you're on your own there. Nobody sells pre-engineered kits for this sort of thing. All design and fabrication is up to you. If you have the skill and money, I say 'go for it' . I drove a supercharged XJR for years and it made a believer out of me. All upsides, no downsides.

You should determine what level of performance you're really after. For some rough perspective, the XJR/6 (such as I owned for years) was supercharged, 4 litre, 4 speed automatic, 4200 pound curb weight. It would do 0-60 in about 6.5 seconds. That was good back in the day; good enough for me. Nowadays, though, an ordinary Honda or Toyota sedan will do better.

If that level of performance sounds good to you then, yes, 300+ horsepower is your goal. If you want to show your tail lights to modern cars you'll need at least 350-400 horsepower. I'd start looking at engine swaps, personally.

Cheers
DD

 

Interesting.
I'd have thought double factory shouldn't be too hard. I've done it in several others.
Might just keep this girl original and look harder for a series 2.
I built one for a mate about 12 years ago with an ls1 and a 6 speed.
Only had 329 at the rear wheels unless you pressed the blue button.
All I can say is thank &@)£ he had a limited brain capacity as well as budget.
My series 2 will feature the bulletproof, blueprinted, 4/87 supercharged ls4 that's in the shed with the hrt custom 7 that's supposed to be in a ***** little v8 supercar. (I've got some interesting friends).
Without the blue button, it will push the equivalent of 748 bhp out of the diff designed for this particular carnivore.
Should I press the blue button, rest assured I meant to die along with whatever was in the same, or adjoining time zone.

 

At this point I'd say you're more qualified than I am to determine how to gain horsepower. I've merely tinkered; you've gone elbow deep

My personal philosophy, developed from the limits of my abilities, is that it's easier to just buy the a car that has the level of performance that I'm after.

My hat's off to the 'can do' people like yourself.

Cheers
DD

 

If you really want to wring some hp out of the old girl, without Lumping her. Why not drop a V12 in the snout? The later 6.0 litre Mill would be my choice. But if you wanted to stay period correct, a well sorted 5.3 would do the job too, especially with a blower.

 

Hi bjsovereign,

These XK engines are well known and well documented to produce good results from modification.

The 'original' 3.4 litre engines were getting 265 bhp in the early 50's at Le Mans under the bonnet of the D Type race cars.

Their output was limited by the need for 24 hour endurance and so limited RPM of under 6000.

With modern day technology, surpassing 8000 RPM is feasible.

Porting the heads seems to get best bang for buck as the later 4.2 litre heads have the enlarged valves already, followed by a different cam shaft profile.

Your best bet would be to get Des Hammill's book How to Power Tune Jaguar XK Engines as that pretty much covers what to do.

Also keep in mind that the XK engine was designed during World War 2 and implemented immediately post war, so the design is a little dated, however, said design was so far ahead of the pack that it continued in commercial production until the Series 3 was phased out in the mid 80's.

Cheers and happy power tuning,

Nigel

 

HMM, what happens when green button is pushed?????

 

I'm guessing the blue button is for the NO2!

 

Curious cats have more fun and learn more

 

The 4.2 in most variations is certainly to be admired. But, it's design and execution is an enigma.


Cross flow head, hemispherical combustion chamber, over head cam shifts. Big time engineering. Great for high RPM breathing. An IC engine is an air pump. Move more air, add fuel, get power, lots of it.


Oh, oh, the longish stroke!! Great for torque at lower RPM's.


Counter productive as I see it.


Why, not an over square straight six?


Politics!!!! Tax based on bore !!!! Odd, or is it. Politico's are generally poor engineers. Total displacement, however generated, a far more logical base for that form of tax.


Oh, that logic thing, huh????


Yeah, one can twist the tail of the longish stroke XK, as well as others, for a time.
But, that time is limited.


Bench racing is fun, only second to the real thing !!!!



Carl

 

Carl, some of our younger USA members might not remember (or even be aware of) "taxable horsepower". Remember that? At least thru the 1960s it was a fairly common thing; the spec pages in owners manuals and service manuals used to mention it.

Cheers
DD

 

we thought it was silly then ,and still do, taxable HP!

theyd have a field day with our newer 650HP cars.

but was reading other day, that India is thinking of some restrictions like that!

but just recently ordered 5000 new Harley Davidson motorcycles, what the hel$ is happening in the world?