I need some help. I have a 1965 Jaguar Mark 2 2.4L and need a head for it. Any thoughts on where I might find one? There is a Mark 1 with a 2.4 engine at auction now but I don't know if the head on this car will be interchangeable with mine. Any help much appreciated.

 

those MK1/MK2 2.4 heads are basically the same.
But the MK1 2.4 engine had small valves and a bit less power. From memory the MK1 had 112hp and the MK2 had 120 hp.
You are not limited to MK2 2.4 heads. the 3.4 heads will also fit on a 2.4 motor.
The only difference between 2.4 and 3.4 motors is in the cylinder/ block system. The heads are basically the same.
However, there are major differences in the intake carbies and manifolds between a 2.4 and 3.4 engine.
But they all work on the same basic head.
I have changed both of my MK1 and MK2 2.4 Jags carby systems to run on the SU HD6 (13/4 inch) carbies.

 

PS
Save the MK1. It will eventually be worth as much as a MK2

 

Basically any XK head will fit on any XK block. As Bill said, the limitations are elsewhere. The A , C and B type heads have different inlet port locations from later straight port heads, which require a different inlet manifold. The last XJ heads don't have the drive for the rev counter generator on the back of the inlet camshaft and have some coolant passages that have to be blocked. All the differences can be overcome. It all depends on priorities: originality, performance, effort in the swap, effort in finding the head, cost of the head.

The 2.4 Mk1 had an A type head (painted duck egg green). I believe it has less camshaft lift and smaller exhaust valves than the B type (painted blue) fitted to the 2.4 Mk2. That might (or possibly might not) have a negative consequence for performance.

 

Wouldn't any B type head fit the OP's Mark 2? Wouldn't any other head from a Mark 2 or S Type be suitable?

 

To my knowledge the Big Valve head (B head) would fit fine ~ but. Jaguar fitted it to later models (Mk2) & were not happy that the car would still not reliably reach 100 miles an hour hence the straight port head on the 240 which could genuinely do 100mph with SU HS6 Carbs & heated manifold. They thought the B head fitted to the Mk2 would make up the performance deficit & it didn't

The 340 with straight port head, which Jaguar kept quiet about, would clobber a 3.4 Mk2 or S Type and Autosport got it comfortably over 120mph on a two way run. (This did nor suit Jaguar's strategy which is why they kept quiet about it when they did away with the 3.8 Mk2).
While cheapening in other areas like no Fograngers & Ambla upholstery both 240 & 340 gained in the engine stakes.

 

Glyn, You mean the big valve or straight port? Either would go. Both, especially the big valve, would probably perform better with less valve duration, if such cams could be obtained.

 

The Big Valve head 2.4 would not do 100 miles an hour. The 240 with straight port head would standard with ease.

"The more significant changes affected the 240, whose engine now boasted a power increase from the earlier 120bhp to 133bhp and a small torque increase from 144lb ft to 146lb ft at 3,700rpm. The main benefits of this were that the car could now exceed 100mph with ease for the first time and that its high-speed acceleration was improved." It was still not a bank robbers car but the 340 was.

 

I thought the big valve head only appeared on the 4.2 Series III XJ6 in 1979? Not counting D Types, which also had bigger valves, but chances of finding a spare D Type head lying about for cheap are zero.

From the specs I have, the Mark 2 2.4 had the same valves (1-3/4"/1-5/8") as all the other Mark 2 and S Type. Actually, everything from 3.4 Mark 1 all the way up to XJ6 Series 2 had the same valve sizes. The 2.4 Mark 1 had a smaller 1-7/16" exhaust valve and the same 1 3/4" intake valve size. The Series III XJ6 4.2 went to a 1-7/8" intake valve, and kept the 1-3/4" exhaust valve.

The only difference I see between the 2.4 Mark 2 vs the 240 is B type head vs straight port, but both have the same valve sizes.

 

JB ~ When we talk about the big valve head we are going all the way back to the early Mk1. This is recorded in a number of Jag bulletins that I would not know where to find easily. At that time the B head was spoken about by Jaguar internally as the big valve head.

The weight gain by the Mk2 offset Mk1 2.4 performance much to Jaguar's displeasure. They thought the B head would compensate over the original smaller exhaust valve Mk1 head.

 

Especially if you can make it look like this car sans narrow rear track. Very pretty.

To me it's either full spat or widen the rear track. Then they look good.

 

Sorry, I was also thinking of big valve as the series 3 4.2 with big inlet valves, while Glyn intended post A type with bigger exhaust valves.

I certainly agreed, wider track, bigger arches and a MK1 looks great.

 

Indeed ~ excuse the confusion. The B Type head as fitted to my S Type was called the big valve head back in the day by Jaguar staff.

 

My 1957 Mk1 2.4 definitely has the "small" valves.
The head was removed about 3 years ago due corrosion and leaking into the coolant system. It required a fair bit of welding to bring it back to original.
The valves were getting pretty ancient and worn but by luck I had a new set of the small valves squirreled away.
Don't remember where they came from; possibly FOT (fell off truck). The valve guides were also replaced.
The engineering shop where the work was done was intrigued. They have done a lot of Jaguar head work but had never come across the small valve head before.

HD6 carbies mounted on a 2.4 engine

HD6 carbies on 2.4 MK2 Note how much lower the carbs and engine sit in the engine bay

 

Apologies
I ended up with MK2 pics in a discussion about MK1 heads. I was going to follow this with some discussion about converting 2.4 engines from Solex carbs to SU HD6 carbs. By the way that grotty wiring to the wiper motor has been replaced.
Cheers

 

I have a 3.4 and my father had the 3.8 so the first time I looked under the bonnet of a 2.4 I was quite surprised by the fact the engine sat so low in the engine bay. There must be at least a couple of inches possibly three in height difference which has to be down to the size of the block.
You can see the height difference here between Bills photo of the 2.4 and the photo of my 3.4 engine pre restoration. Note the position of the coil on the front of the engine.

 

I have one

 

All of this is most interesting. I thank all of you who have resopnded. What I have taken away from this discussion is that a 3.4 head will fit onto a 2.4 engine but will need a different intake manifold. As it happens, I have a rebuilt 3.4 head ready to go. I also have a triple carb set up. Do you think that this will work in my 2.4? Second question since I still have the 2.4 head, will the 3.4 valves and cam shafts fit into the old 2.4 head should I decide to redo it? I have no idea where the old 2.4 valves went.

 

I don't think you will be able to get the triple carbs under the bonnet of a Mk2 without some serious modifications to the inner wing. I think it would be even harder on the 2.4 because of what we mentioned earlier in the thread about the block of the 2.4 being shorter and there for sitting lower in the engine bay so the trumpets of the carbs are going to be even closer to the inner wing which slopes in as it goes down. Do not be foolish in thinking that if you can get them down the side of the engine that you would then run them without any air filters. Just after my restoration I was test driving the car tuning the carbs which needed the air filter housing to be removed. I had a small piece of gravel/road chipping get sucked into the mouth of one of the carbs but lucky for me it jammed in the butterfly of the carb. Scary for two reasons. First the chipping could have got into the engine and because of it size would without doubt have destroyed an inlet valve, piston top and bore. Secondly because it got caught under the butterfly I could not stop the engine from revving up and my car is an Auto so no chance of dropping the clutch to slow the car down. Had to switch the ignition off to kill the engine. So an experience learnt the hard way, never run a carb without an air filter.
This was the size of the road chipping next to a AA battery.

 

The 3.4 head will fit just fine but there is no space for triple carburetors.