Exactly asI have stated in my post Roger, but are you aware of a major difference in the 240/340 heads that blows you assertion of a “huge problem” out of the water
I suggest you read my post again and regard the photos re the 2.8 manifold.
Peter B
Peter,
Suggest you reread my post.
I said problem with straight port heads as fitted to XJs, was age related, and approx 1970.
Clearly that doesn’t include 240/340 which are pre1970.
Roger
Please, stick with originality. It’s a truly beautiful car - if you want something else, sell it and buy that something. In a changing world, originality will be counting for more and more, believe me…
Roger for your education the late 240 was fitted with the XJ casting with the extra water ways EXCEPT the holes were not formed , ie the casting was left BLANK so it will have a different part number compared to XJ.
By extension if with the water ways blocked the head is suitable for the 2.4 block then it’s suitable for use on 3.4 and 3.8 blocks, so when using the pipe plug method or welding the holes prior to refacing, where’s the “HUGE PROBLEM”?
This blanked head might be fitted to some late 420Gs also, the very late 420Gs having a slightly different block to the early 420Gs and I don’t mean the central engine mounts IMHO this late 420G block,with the head studs in the block face, is the best of the bunch.
Peter B.
Bit late in replying Tony, but yes engine and carbs in car.
Rather than post in this thread I`ll try to tind the original. where I will offer some thoughts
re fuel supply etc
Yes lot of metal in the Tens.
Peter B.
More picture’s Mike, nice engine and gearbox, magneto ignition takes over the rpm from the generator?
The magneto (in this case, a Swiss made Vertex) is entirely independent of the vehicle electrical system. It generates it’s own current. If you can push the car, it will start.
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Hello guys. I have not forgotten you, but it was super busy at work for me. I will come back with my thoughts on conclusion very soon. I am very glad to all the information I got from you all!
Hello all!
Some news to share with you 
I bought two cylinder heads! Why? Because I wanted to leave both options open until the end, then I will sell the unused one.
- MK2 3.4L B-type head with inlet manifold
- 420 SP head early with no extra water holes and no bump in back with inlet manifold from a XJ6 2.8 that will be the easiest fit to my water hose and thermostat.
I am planning to go for the second one as it should deliver more power, and the manifold already has the 2" inches openings for my HS8.
Would someone be able to estimate the power it should give ? I will be in a XK150 3.4 S configuration, excepted that I have only 2 HS8, instead of 3 HD8, so it’s exactly the “Jaguar mk2 340” configuration actually.
I know the numbers are purely theoritical, but in the old SAE gross I think it could be between 210 and 250. Would 225 be correct ?
In reality, DIN net, I would expect at least 160 maybe 170 ?
I will do a power bench test to confirm that anyway.
I also hope that the SP head will not make me loose torque compare the B-Type head and thus is a win at any revs!
Any recommendation on which head gasket to buy? (material or version ?)
Pictures should be made this weekend.
PS : Massive thank you to peterjb who has been coaching and training me since the beginning of this adventure!
The head, alone, with proper jetting, can be reasonably be responsible for 25-40 more horsepressure.
I’d use the Cometic gasket: if the deck and head have been surfaced, the thin steel will be good.
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Yes my SP head was surfaced. About my block, no clue on how it will look like. Let’s see after the dissemble. I am planning to do the whole operation with the engine inside the car.
Nobody has mentioned the cylinder head on the 3.4/3.8 S Type, that was around from about 63 -68. I have one of these fitted to my 120FHC with two 2” HD8’s. What is the difference between the heads on MK2, 420, S Type ?
I think yours is a B-type head (MK2, S-type, XK150, etc), versus the Straight Port head (240/340, 420, E-Type, XK150S, XJ6, etc…)
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Interesting data sheet. What is the actual difference between an A, C and B type head ? Also there seem to be several different intake manifolds.
I think it would take a long answer to really detailed any differences, but I had the same questions initially and found the majority of answers on the internet, on this forums and on this topic now…
Jean, very interesting data sheet, now I know which colour I will give the 3.4L engine from a Jaguar XK 150 1958, working on it now.
It’s light Green, nice. Bought one can from Sng.Barratt.
Painted the sump and new pistons.
Frank.
Jean,
Don’t know where you copied that listing from, BUT there are errors in it, so at best a general overview only, and not a credible reference.
Roger
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Actually the more I look at it, the worse it gets.
It’s rubbish, so many errors it’s not funny.
Roger