MK2 2.4 minor power upgrades

Hi all! This is my first post on this forum, excited to have joined. This lockdown, I’ve bought a fairly tidy mk2 2.4 for little money from a film company’s inventory. It was a really nice project to get it running better, service and fix things, clean it up, style it a bit and drive it around. It’s a lovely thing!

With a stock 2.4 engine with Solex carbs, it’s not particularly fast. Being aware of its limitations, I was wondering to what extend more minor modifications could be undertaken to make the car a bit more lively.

Three initial ideas (before going too crazy!):

  • does it make sense to upgrade from the stock Solex carbs and intake? For reasonable money I could buy a 3.4 B head intake manifold, and a pair of 1 3/4” SU HD6 carbs. Does this make a difference over Solexes?
  • would a Jaguar 240 dual exhaust system fit, or be made to fit? Having two pipes would probably enable the engine to breathe a bit better (and it’ll look nicer)
  • in my experience, electronic ignition is a nice upgrade for any vintage car. Any experiences adding this to a 2.4, or any mk2?

Looking forward to hearing from you all! Regards Adriaan (Surrey, UK)

Hi and welcome , 2.4 with a A head and Solex carbs is around 112 bhp , 2.4 with a B head with Solex carbs is around 120 bhp , 240 with the straight port head with HS6 SU cards is around 133 bhp .
340 engine is around 210 bhp .
I don’t know but would think the twin exhaust should help the bhp , and not sure if the twin heat shield under the car is just a bolt off bolt on job
Not sure about the exit of the twin pipe over the single , in back valance for room , I guess if not enough room you could just add straight pipes from the back boxes , look Coomb’s did :thinking:
I still have points and condencer , been ok for the last 40 odd years , only about 20 to go :scream: lol

Adrian,Enjoy the new car and welcome.
Drive the car for a bit and get to know how it responds.
I bet after a while you will do less and less other than enjoy the car for what it is.
As others have said with the above upgrades you can gain MAYBE 15 hp on a 55 year old car?
Simple upgrades Imho such as a 123 ignition and a set of ngk plugs make all the difference in the world.
Drive it, clean it up and enjoy it!
Every Honda Accord will blow your doors off!
It’s time fore “grace” not “race”!

1 Like

That would be the least expensive and likely best mod one could employ: later on, if further mods, like head, carbs, and exhaust are pursued, it will remain a helpful mod.

Thanks guys, that’s helpful. The last couple of months I’ve been setting up the Solexes as good as possible, and with servicing the car thoroughly, playing with tyres and road set-up, and the odd ‘Italian tune-up’ on a Sunday morning, it has come to life a bit more and is turned into an enjoyable drive. I think another 15 horses combined with some more exciting intake/exhaust noise could liven things up a bit though.

It sounds that a combination of the new SU HD6 carbs + manifold, a dual exhaust system from a 240 or potentially done by an independent shop and a 123 programmable ignition would be a nice place to start without breaking the bank. Good point re the ignition system; indeed very helpful for any (future) mods to keep that flexible and reliable.

Am fully aware that the gains might be limited, but I think the process sometimes is just as much part of the enjoyment as the end result, therefore keeping modifications in the ‘reasonable’ category cost-wise. Happy to hear any other suggestions how to improve it further as a drivers car!

You don’t say if it’s manual or auto. If auto and you want more responsiveness change to manual. I have two overdrive gearboxes for $100 each plus shipping.

Jaguar issued a booklet (E/112) that covered 3 stages of tune for the 2.4, Google The Coventry Foundation for a copy.

Hi Peter! It’s a manual O/D. A flush and some Red Line gearbox oils combined with a slightly lighter gear knob have improved shifting quite a bit from when I bought the car, but indeed it’s rather not rushed;)

In Paul Skilleter’s book, Jaguar Saloons, he relates the story of the editor of Road and Track magazine modifying his personal 2.4 Mk1 ( which, of course uses the same engine and carburation but with the B Type head) The short story is that having upgraded to 1 3\4 SUs on an XK140 manifold and various other mods there was an increase in top end horsepower of 2bhp and a loss in the medium to high range. The tuning booklets mentioned earlier came in 3 stages and provided claimed power of, respectively, 119 bhp, ( mainly carb mods), 131bhp, ( Stage 1 plus 3\8 lift cams) and 150bhp ( B Type head plus 1 3\4 SUs). Quite why a Mk2 2.4 which already has those features only produces 120bhp on Solexes or the 240 with straight port head and SUs only produces 133bhp is not clear to me. FWIW, I’ve owned a couple of 2.4s and never really found them wanting for power; certainly not in same league as the bigger engined cars but certainly adequate. Smoother and driven appropriately more economical too. BTW a MK1 2.4 with low lift cams and A Type head (112bhp) is actually faster than a 120bhp Mk2.