Jaguar Mk2 3.4 / 3.8
Discussion
I'm toying with the idea of buying a Jaguar Mk2 next year. Having driven a Mk2 2.4 for many a year I'm reasonably familiar with the model but just fancy a bit more power. As such I have a number of questions mainly around differences between the 3.4 & 3.8 and sensible modifications to improve things a bit without the need for a second mortgage:
Q. Is there a noticeable difference in performance between a 3.4 and 3.8 ?
Q. The 2.4 has non-assisted steering which is a bugger at slow speeds but gives good feel as the car speeds up. I've read that fitting a 420 power steering box is a good solution however my experience of power steering systems of this era is that they are overly light and my concern is I would loose that feel.
Q. Improving the braking is quite high up on the list of things to do. I've seen a number of cars advertised with Coopercraft brakes, is this the de rigueur option ?
Q. In terms of engine modifications, cost has to play a factor. It's going to be quite a step up from 2.4 to 3.4/3.8 but then I'm thinking a bit more performance would be nice, the only thing is having no idea of relative cost, thoughts of putting a straight port head on with larger carbs is maybe pie in the sky and there maybe a more cost effective alternative
Q. Is there a noticeable difference in performance between a 3.4 and 3.8 ?
Q. The 2.4 has non-assisted steering which is a bugger at slow speeds but gives good feel as the car speeds up. I've read that fitting a 420 power steering box is a good solution however my experience of power steering systems of this era is that they are overly light and my concern is I would loose that feel.
Q. Improving the braking is quite high up on the list of things to do. I've seen a number of cars advertised with Coopercraft brakes, is this the de rigueur option ?
Q. In terms of engine modifications, cost has to play a factor. It's going to be quite a step up from 2.4 to 3.4/3.8 but then I'm thinking a bit more performance would be nice, the only thing is having no idea of relative cost, thoughts of putting a straight port head on with larger carbs is maybe pie in the sky and there maybe a more cost effective alternative
Have you looked at what is involved in swapping the engine?
At one point I'd thought about producing an dyslexic Mk2 (a 4.2 in a 2.4)
Given the current cost difference between a 2.4 and a 3.8 it could well be cheaper, 4.2 engines aren't hard to find. That way you'll be keeping a car you know rather than risking one you don't.
As well as the Coopercraft brakes there is also Zeus, these don't look as good once they've seen some life but some people claim they are more reliable. You can also just look at the pad materials to improve the braking.
The later 240 used the straight port head, but I think it was more to limit inventory. The straight port produces more top end power just the B-Type head produces a better torque spread. Back in period there were triple carb manifolds available for the B-Type and some XK racers still prefer them. Of course a 4.2 would give you lots more torque anyway.
IIRC you need to make some changes to the inner wing of a Mk2 to get triple carbs in there. You can certainly swap the 3.8's standard HD6's for HD8's, but you'll need to change the air filter arrangement.
At one point I'd thought about producing an dyslexic Mk2 (a 4.2 in a 2.4)
Given the current cost difference between a 2.4 and a 3.8 it could well be cheaper, 4.2 engines aren't hard to find. That way you'll be keeping a car you know rather than risking one you don't.
As well as the Coopercraft brakes there is also Zeus, these don't look as good once they've seen some life but some people claim they are more reliable. You can also just look at the pad materials to improve the braking.
The later 240 used the straight port head, but I think it was more to limit inventory. The straight port produces more top end power just the B-Type head produces a better torque spread. Back in period there were triple carb manifolds available for the B-Type and some XK racers still prefer them. Of course a 4.2 would give you lots more torque anyway.
IIRC you need to make some changes to the inner wing of a Mk2 to get triple carbs in there. You can certainly swap the 3.8's standard HD6's for HD8's, but you'll need to change the air filter arrangement.
A dyslexic Mk2 appeals although not being mechanically minded, how easy is it to put a 4.2 in?
Having said that and without wanting to appear too contradictory, I'm somewhat reticent to change the car too much. I'd like to keep things as original as possible albeit that opens up an enormous can of worms over what is "original", trigger's broom and all that.
Just to clarify I'm looking to buy another car and not modify the 2.4 if that makes sense.
Having said that and without wanting to appear too contradictory, I'm somewhat reticent to change the car too much. I'd like to keep things as original as possible albeit that opens up an enormous can of worms over what is "original", trigger's broom and all that.
Just to clarify I'm looking to buy another car and not modify the 2.4 if that makes sense.
Edited by Bobo W on Monday 23 November 16:04
From memory, not a lot of difference between the 3.4 and the 3.8 litre engines, 210 to 220 BHP and another five miles per hour top end but I think the 3.4 is a more balanced engine, less oil consumption and possibly less likely to have been driven as hard..
Fantastic cars both though and a Coombs style 3.8 with two inch sand cast carbs and ported head is a wonderful thing
Enjoy sir
Fantastic cars both though and a Coombs style 3.8 with two inch sand cast carbs and ported head is a wonderful thing
Enjoy sir
I've got a 3.8 and previously owned a 3.4. Unless you're intending to drive like a hooligan they're both more than capable of mixing it in modern traffic.
Considering these cars are now 50 years old almost every one you drive will have been restored, rebuilt or modified to some extent and it's difficult to say how a "typical" car will drive. I've driven a few this year as my friend is looking for one and all of them feel quite different.
My 3.8 is very original and totally unmodified. The steering is probably it's weakest link.
My previous 3.4 was also very original when I bought it, but I fitted power steering, uprated the wipers, fitted an alternator and a few other mods. It was very nice to drive but not as fast as the 3.8 I now own.
Be careful which power steering system you fit, some of them are very badly engineered.
If you want a bit more power I would suggest a bit of work on the head and a slightly hotter camshaft is one way to go. I wouldn't bother with a triple carb setup personally. As a previous poster said, you could drop a 4.2 engine in, but it would certainly devalue the car.
Really it depends on what you intend to use the car for. In standard form they're fine, but if I was going to use one as an everyday car I think I'd do something about the steering and the wipers as a minimum.
Considering these cars are now 50 years old almost every one you drive will have been restored, rebuilt or modified to some extent and it's difficult to say how a "typical" car will drive. I've driven a few this year as my friend is looking for one and all of them feel quite different.
My 3.8 is very original and totally unmodified. The steering is probably it's weakest link.
My previous 3.4 was also very original when I bought it, but I fitted power steering, uprated the wipers, fitted an alternator and a few other mods. It was very nice to drive but not as fast as the 3.8 I now own.
Be careful which power steering system you fit, some of them are very badly engineered.
If you want a bit more power I would suggest a bit of work on the head and a slightly hotter camshaft is one way to go. I wouldn't bother with a triple carb setup personally. As a previous poster said, you could drop a 4.2 engine in, but it would certainly devalue the car.
Really it depends on what you intend to use the car for. In standard form they're fine, but if I was going to use one as an everyday car I think I'd do something about the steering and the wipers as a minimum.
medieval said:
Fantastic cars both though and a Coombs style 3.8 with two inch sand cast carbs and ported head is a wonderful thing
The last Mk2 I drove was one that Ken Bell had built for a customer as a recreation of one he'd built back in period. There was an article about the car in "Jaguar World Magazine". The original had been built for a gentleman racer to use as his car during the week and his racer at the weekend. That certainly went well 
and was running a brace of 2" carbs.
Totally off topic question, Would the Combs cars have used the "Sandcast" carbs, I would have thought they'd have used the regular HD8 like the XK150S, E-Type and Mk10. I thought that the only sandcast SUs used by Jaguar were on the C-Type and as an option on the XK120 & XK140 which were all H8s. But I see that Burlen list a Sandcast HD8 conversion kit for the 420.
I'm pretty sure the one I drove had main sequence production carbs, rather than the sandcast ones.
See, I said it was off topic. Sorry OP.
There's a strong argument for fitting a hotter cam, tubular exhaust manifold, the straight-port head & either twin HD8s or triple HD6s to your 2.4. The head & triple carbs should be readily available off a dismantled Mk X or 420G.
The 2.4 is a smooth revvy little unit & a tuned one would retain your car's originality, render it almost unique & be readily reversible should you or a subsequent owner want to return it to stock spec.
Obviously a tuned 2.4 would depend on rpm for its performance & not be a relatively lazy motor like the 3.4 & 3.8 - so getting it balanced would pay dividends, if you can run to the expense of a tear-down.
The 2.4 is a smooth revvy little unit & a tuned one would retain your car's originality, render it almost unique & be readily reversible should you or a subsequent owner want to return it to stock spec.
Obviously a tuned 2.4 would depend on rpm for its performance & not be a relatively lazy motor like the 3.4 & 3.8 - so getting it balanced would pay dividends, if you can run to the expense of a tear-down.
As for the performance difference between the 3.4 and 3.8 there isnt really a lot, Ive had 3.4's an 3.8's over the years and currently own a 3.8 manual. The big plus of a 3.8 is that it had a powerlock LSD fitted as standard, The 3.4's didnt, Top check when buying a 3.8 is to ensure that it still has its powerlock diff fitted. The fact the 3.4 is smoother than the 3.8 has been stated alot and in my experience it is true especially up near the red line, The 2 3.8's ive owned have been a bit harsh there but every engines different i suppose. All flavours of the XK engine are getting harder to find, Search for a 4.2 on ebay or gumtree now, There arent many being offered of all cc's and Jag specialists want an arm and leg for them. As for tuning a 2.4 i feel it would be more cost effective putting in a good used 3.4 or 4.2 if you can get one, The cost of rebuilding/Performance upgrades on XK's is huge.
I've had a few over the years. If it was me I'd not even consider the 3.8 since that is the car that is sought by testosterone people with - nowadays - testosterone budgets. The 3.4 is sooooo smooth, so easy to drive and you lose nothing in performance that you can distinguish. It'll cost you a darn sight less and with the extra you can add electric power steering which is powered at low speeds and cuts out as speed increases. Why on earth consider a 4.2 engine? The 3.4 is the best of the lot, as aforesaid.
I have Zeus brakes on my E-type, and after nine years and lots of miles in all weathers the seals needed replacing, but that's not a big deal. Zeus designed the braking system for London taxis and they were sold by Coopercraft. Now the two are in competition. There is really no difference, and I can tell you that compared to the old 3-pot callipers with miniscule pads the E-type can now lock up all four wheels. It's just that Coopercraft is the known brand.
So, buy a 3.4 in the first place; you won't regret it. Then with the money saved add electric power steering or else stick to crossply tyres as I did. But why would you want extra performance? Are you going to drive it like you stole it? I doubt it, and my Mk 1 3.4 manual overdrive would cruise all day at 80 mph.
I have Zeus brakes on my E-type, and after nine years and lots of miles in all weathers the seals needed replacing, but that's not a big deal. Zeus designed the braking system for London taxis and they were sold by Coopercraft. Now the two are in competition. There is really no difference, and I can tell you that compared to the old 3-pot callipers with miniscule pads the E-type can now lock up all four wheels. It's just that Coopercraft is the known brand.
So, buy a 3.4 in the first place; you won't regret it. Then with the money saved add electric power steering or else stick to crossply tyres as I did. But why would you want extra performance? Are you going to drive it like you stole it? I doubt it, and my Mk 1 3.4 manual overdrive would cruise all day at 80 mph.
A 4.2 was suggested as a used replacement as it was in production to the end of 1986 with the 3.4 so there may be more about? Also the later 4.2's bigger valve head (EFI's) cant be a bad thing? As for brakes the 3 pot caliper pads are a good size if the ones on my S1 XJ are anything to go by, Its the original dunlop calipers that had the small pads. As for the testosterone budget comment, What? People who throw blank cheques at restorers sort of thing?
Edited by klunkT5 on Sunday 29th November 23:40
Not at all. My comment was referring to people who know little about Jaguars and think that the one to have must be the 3.8. It's bigger so better, innit? Whereas, since we don't tend to do traffic light starts every day, to those in the know the 3.4 is the better and far smoother engine of the two - and since it isn't perceived to be the best is by far the best value. But then I'm talking of buying a complete car. If you are in many ways building your own to your specification then anything goes, and the best of luck to you. I had a quick shufty here:-
http://www.carandclassic.co.uk/list/22/mk2/
There again, the later Ambla-trimmed small-bumper 340 is in my humble opinion the best value of the lot.
http://www.carandclassic.co.uk/list/22/mk2/
There again, the later Ambla-trimmed small-bumper 340 is in my humble opinion the best value of the lot.
lowdrag said:
Not at all. My comment was referring to people who know little about Jaguars and think that the one to have must be the 3.8. It's bigger so better, innit? Whereas, since we don't tend to do traffic light starts every day, to those in the know the 3.4 is the better and far smoother engine of the two - and since it isn't perceived to be the best is by far the best value. But then I'm talking of buying a complete car. If you are in many ways building your own to your specification then anything goes, and the best of luck to you. I had a quick shufty here:-
http://www.carandclassic.co.uk/list/22/mk2/
There again, the later Ambla-trimmed small-bumper 340 is in my humble opinion the best value of the lot.
Ah, lowdrag, you are now showing the true depth of your Jag knowledge. The 3.4 is indeed the finest XK engine, and I can state that from over 40 years of pulling the things to bits and rebuilding them. The problem with the 3.8 is piston slap; almost impossible to cure unless you go seriously upmarket with things like oversize forged pistons. Most of these have an extra oil control ring at the bottom of the skirt helping to stabilise the piston and cut down noise.http://www.carandclassic.co.uk/list/22/mk2/
There again, the later Ambla-trimmed small-bumper 340 is in my humble opinion the best value of the lot.
The 340 model is lighter, has a more elegant appearance, lower front end drag and has the benefit of a straight port head and ribbed cam covers that don't leak! The Ambla upholstery can be re-trimmed, because it is simply horrible to sit in on a hot day and smells of cheap plastic.
I had a beautiful 340 I bought from a retired bank manager in Imperial Maroon and he had ordered it from new with black leather. All I did to it was fit an alternator and 2 inch carbs and it was fantastic. The best MK2 I've ever owned.
The S3, big valve head was very badly built. Remember this was the height of the BL days and quality control was virtually non existent. They would go porous, suffer from loose cam follower guides and premature cam and follower wear. The only way to use one of these heads is to have it totally rebuilt before fitting and the faults engineered out. On top of that they won't do you any good unless you raise the compression and run injection or Webers: and expect seriously increased fuel consumption.
Jaguar also used to do quick ratio steering boxes for the MK2 and S type. They weren't power though but made a huge difference to the steering response. Be like hen's teeth now I'd imagine.
Stick with the 3.4!
J
klunkT5 said:
A 4.2 was suggested as a used replacement as it was in production
The only reason I'd suggested the 4.2 was that the OP has a 2.4 and wanted more power. Rather than moving from a car he knew to another I'd suggested that he could look at upgrading his current one. It turns out that wasn't what he was after.
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