Hi all I,m still kicking and screwing cars together ! Heres my question Jaguar produced the series 3 XJ with a 3.4 engine The cylinder head is a straight port will it fit a 3/4 -3/8 block and has it got the extra 2 water ports like a 4.2 head I,m looking to replace a porous head on my 150s Irealise there may be some machining on the inlet side Regards to old friends and new Terry Hilton Australia
I read all XJ6 blocks and heads have the same extra water ways at the back , I think its just a case of blocking the extra holes up in the head !
I was hoping the seris3 XJ 3.4 head was same as the 2.8 and the 340 head I have one here off a 420 that looks like it would be ok Hasnt got the bump on back of head It would need some machining on the inlet side The 4.2 heads just dont look right Regards Terry Hilton Australia
someone here in WA advised me recently to solve this problem of fitting the late head onto an early MKII block he weld a piece to the back of the block and I believe incorporated these water ways into the block.
I am looking at the car in a week and a half will take photos
terry
Plugging the two extra holes at the back of the head is the easy part. If you want to retain the cable drive mechanical tachometer it gets more complicated.
Why do you think the 420 head doesn’t look right? It wouldn’t look much different than a 3.4 head of the same vintage. What does look different is the intake manifold. No problem fitting the straight port head to the block, but the intake manifolds from the A and B heads won’t interchange.
What do you think needs machining on the intake side?
That’s what I will be doing soon , fitting the generator to the back of the head , the engine is a 75 3.4 xj6 , may or may not drill the 3rd hole for the generator , the 2 side holes are in the head , but the bottom one has not been drilled and taped .
3/8 tap come today to tap the back hole in the came shaft .
You do need a early cam bearing top for the back as well , as the generator seals with it !
I like your air filter! Here’s mine:
Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2
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Excuse my ignorance here. But what is that dual carb intake from that mates to a straight port head? That looks very pretty by the way.
Follow on ignorance… what are all the potential straight port heads that I could use on a 3.8 without needing to do waterjacket mods or other mods? I have an etype that I am building a motor for and trying to find a reasonably priced straight port head to use on it. Block and crank are a super clean 3.8 from a S-type.
I will eventually try to source a correct e-type head/block for it as well but I want to build this motor to be a driver that I put some mileage on.
Thanks!!
Hi Mike Good to hear youre still around ! I,m wanting to use a head for a 3 carb (150S ) application on my car . The 420 and xj heads aii use a one piece inlet manifold The 150S uses 3 separate pieces with the water return in the middle of the 2 inlet ports On the original head Jaguar Plugged the 2 large water jacket holes with 2 big hexagonal plugs The only water return being the 3 piece manifold . The 4.2 head with its 'bump" at the back gets awful close to the firewall Regards Terry Hilton Australia
Terry,
Not the kind of questions I thought you would be asking - you know more about XK engines than most.
Its an age issue re compatibility of XK heads.
All the early XK heads up to about 1969/70 will interchange on all the same age blocks - same head gasket.
But in mid Series 2 E-type/Series 2 XJ period to address a cooling problem developing due to emissions controlled engines/airconditioning load etc etc, the water jackets were revised that extended both the head and block rearwards, thus the ‘bump’ you refer to. So all XK motors thereafter, the later head (weather 3.4 or 4.2) will fit onto later block (3.4 or 4.2) with same common head gasket (pattern that is, materials did change). But a later head (with a bump) will not fit onto an early block, and vice versa - without BUTCHERY and a poor end-result.
Recently, I reluctantly sold a really superb/original/uncorroded Straight-Port-Head ex a 3.8 Mark 10, to a local 1966 E-type owner who asked me for help after his original head cracked (and his engine rebuilder advised unrepairable). Part of my reluctant sale of this head was I wanted his cracked head back rather than scrapping it - just as a handy reference head from 4.2 E-type. A couple months later, he rang to drop head around, and on receiving it, it was Series 3 XJ head (with the ‘bump’. Seems his car had a replacement engine in it - block and head ex S.3, and his Engine ‘expert’ had trouble fitting my Mark 10 head (of course), but welded up the back of my head sufficiently, that he could machine water-passages to line up with extension at back of his Series 3 block. Car was running OK (for now) so he was happy, but if I had known spare S.3 heads are cheap and plentiful, and I have now lost for ever a perfect early Straight-Port-Head.
Your 420 head will be early head (and a straight-port-head at that), so will happily bolt straight onto any block - but being a straight-port head, will need a compatible straight-port-head INLET MANIFOLD, as per your 3 car (150S) manifold, so all should be straight forward. Don’t waste your time playing around with a later 3.4/4.2 S.3 XJ head - leave it for anyone with a S.3 block.
Roger
I like the clean look of the early cam covers. It’s a good way to hide the head swap from the casual observer.
Ahhhh… The secret manifold is from a North American Series II 4.2L E-Type. it is barely visible in the attached photo. It doesn’t look that way on an E-Type, because it is buried behind two Stromberg carburetors and under all of the add-on hardware it took to make them pass the emissions testing. For years, I would look at these beautiful E-Types, bonnets raised at shows, only to expose the formerly beautiful XK engine swaddled in the most awful Rube Goldberg add-on crap of emission controls. I would often ask the owners why could you not eliminate all of that crap and bolt the carburetors directly to the manifold. They always gave me a horrified look and cast me away like the heathen Philistine that I was, and I never saw a car done that way. Of course, anyone who now owns a Series II car has likely converted it to the tri-carb Series I setup by now, so these manifolds are relatively plentiful and generally cheap.
I use the K&N equivalent of the WIX 99897, originally for 1980-1989 Subaru. I drew up the front and back plates in AutoCad, then had them cut out of 0.090" aluminum with a waterjet.
http://www.wixfilters.com/Lookup/PartDetails.aspx?Part=99897
I used the same filter, drew up the front and back plates on a piece of
aluminum and cut them out with a saber saw. ;^)
Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2
I have not touched a saber saw to metal since I discovered the waterjet.
Matt,
Popular modification for Mark 2 saloons, is to fit a early (pre-1969) straight-port-head directly onto the original 3.8 Mark 2 block (so will fit onto any 3.4 or 3.8 block apart from the UK only 3.4 XJ block), and then use an INLET MANIFOLD from a 420 saloon, which of course fits straight onto a straight-port-head, but also accepts twin 2" HD8 SU carburetters.
You can use a Series 1 XJ6 INLET MANIFOLD as well, but gets fiddly around thermostat housing/top radiator hose whereas 420 manifold has no complications. With a Mark 2 - triple SUs don’t easily fit, without major modifications.
With an E-type installation, due to closed- bonnet clearance issues, you do need an E-type Inlet Manifold (as that angles carbies down a little) and short-neck HD8 carburetters, so be a bit careful about mix and matches.
Roger
That makes sense, I hadn’t thought about those later E-types since I have been focusing all my learnings on the Series 1. Mine is an aluminum dash 63 rust bucket. 
What all variations were there to the straight port head? Is the 420 Saloon straight ports the same as the e-type? Are there others? I will still run the triples most likely (I like the idea of fuel injection still for practicality on a car that I am going to drive a LOT).
I am still looking for one to either build myself or use as a core exchange for a Cat Claw head. I have a really good buddy that works on some incredibly rare exotics (think lemans gull wings and 1 of 3 in the world ferraris… etc at a place here locally called VRM) and he has offered to build me a head so thinking about taking him up on that but also like the idea of a Cat Claw just because they have spent a long time learning to make power out of these…
Hi Roger The unit in question isn,t far from you Its a 3.4 xj motor They were never sold in this country , so it must be a private import ive never worked on one My query is about the stud spacing and whether the head will go on to a 3.4/3.8 150 block . I recollect ,that on my last visit to davids The motor was in the paddock with an unmachined straight port on a 3.4 XJ type of block I cannot recollect if it had the two extra water ports, and hence the bulge at the rear. If the head studs line up ,then the machining required to close off the 2 INLET side water outlets is easy , Neil K says he can use the block , I know hes building a LWT- E type ,but cant see it any use on that project Will advise when i see the head Terry Hilton Australia