I realize this will go against the grain of the purists, but if someone needed to replace an engine, what would be the best year of 4.2 engine. I know the oil pan would have to be changed out, but what else may need altering? A rebuild of the ‘correct’ engine would run into the thousands, so a replacement would be a good temporary fix. Of course, save the original, numbers matching frozen engine.
on the table of elements aluminium…IS the correct spelling…jeesh…
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IMO. the best motor to use would be the short stud 4.2 from a Mk10, 420 or E Type. They don’t suffer the headstud corrosion issues of the later blocks and the specific E Type parts will swap straight over, plus you could always fit a big valve S3 head if you wanted the extra power. Longer lasting, fewer head gasket problems too.
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What I have is a 1967 E-type 2+2 with a stuck 4.2 engine with triple carbs. I have thus far tried the various snake oil recipes to free it up, but so far, none have worked. I was thinking of a temporary ‘substitute’ engine to get things going, and the XJ6 replacement was an idea that came to mind. I was wondering it the 83 to 87 engines would work, as those I have seen were all fuel injected, and that may be the basic block/head configuration was altered. Lots of them out there still in cars that are going for very reasonable prices. Guess the best of all worlds would be to buy a running car with low miles. Talked to a few ‘experts’, and they say a rebuild of my engine could cost 8 to twelve thousand. Thanks for the info on the ‘newer’ engines.
I have an S2 XJ engine in my E-Type. The blocks and heads from any XJ through '87 will work with a bit of fettling, things like plugging air injection ports. But the EFI bits can’t be stuffed in. Your intake and exhaust manifolds will bolt right up to any XK head.
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Micheal is correct…ANY XJ6 engine will work…
Early manifolds, with and without carbs come up on Ebay from time to time. Complete setups are pricey. Like three thousand for a nice one. So many were grabbed up for swaps to later E-types, and you see it all the time on Bring a Trailer.
I am going to search out an 80’s xj6 car or engine. Thanks so much for all the help and advice.
Hi I do have a 66 2+2 with a replacement engine running atm and the original engine is being rebuilt I will be selling the replacement when all is done
Message me on the replacement engine, and I may be interested. thanks ron
Ask yourself this question. Who is likely to buy this car, and with what intention? My impression is you want this thing running to get a better price for it, or that’s what you implied in a previous topic.
So a prospective purchaser would be wanting what? A runner? This car obviously needs a total rebuild, and whichever way you look at it, it will be touch and go as to whether it’s a viable proposition, but would a buyer be more likely to buy because it has a running XJ6 engine in it, that A: has cost you time, money and effort to locate and install and B: will take time, money and effort to remove because the car is less valuable with it fitted. Even with a running motor, the car still needs a total rebuild to be usable, so why bother at this point? If you must tinker to keep yourself entertained, why not pull the head and find out why the current engine is seized? You might be lucky and find something relatively simple; remember, pulling the head is a lot easier than pulling the engine. I’ve actually done rings and bearings on both my E Types without pulling the engine; it’s actually easier than doing the same to a Mk2.
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Primer it up…and it is our scruffy,scruffy…La Bamba. Our La Bamba
And drive it and drive it and drive it
Mitch
PS…it’s rust free
Just FYI, a Lucas “Universal” 75A alt looks very much alike to the AC11, fits in easy, has 2 wires, one to the ignition light, bypasses all the external regulator parts but I still run my original ammeter
Its a big job to pull an engine and trans, swap the ancilliaries, complete sensible other cleaning and improvements that can only be done with the engine out, then put it all back together
I hope the OP is feeling spry, I could do things like that in my 50s without any trouble at all, but now I see why guys in their 60s are so fond of hoists
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When I was racing one I opted for the later blocks that came with the fuel injected head. The blocks are slightly lighter, and have sculped sides with external ribs. These blocks are all long studs, the studs going into the upper casting for the bearings. I was of the opinion / told (?) that those were superior to the short stud block but can no longer remember why I thought that. Some have the saw cut between cylinders. Inspection of the block through the frost plugs showed better internal cooling passages, and as well there were many more water holes between the block and the head. My last engine was one with the saw cut - it put out 375 hp on an engine dyno, never ever overheated, and with a modified f.i. head was dead reliable for 7 years.
Its written the longer studs down into the saddle gave better rigidity with respect to the the block, and I think it was supposed to help the head gasket union
As you know, the real drawback of the longer studs comes about as they have a tendency to corrode into the block at the very base, and snap off
This is actually a very serious consideration for any buyer of an XJ engine, as they are a minimum of 35 years old, almost all of them will have this potential timebomb
Its actually so bad % wise that it would almost be mandatory to renew the core plugs just to inspect them prior to installing an engine
I have a short stud 4.2 block, and that one I will keep, the studs came out dead easy
Just all of us “talking our book”…really a human trait be-it a very bad one…not being objective…
This being said…I have several long stud 4.2 in storage…should I pull the core plugs…should i fill with mystery oil or oil and re-install a core plug…what should I do for storage…I would quess these will be used after I am dead…30 years
2nd…Richard W…mentioned to me (like 7 years ago) can just cut the long studs off…then treat as a short stud…have no idea what this means…but it swims in my head…anyone ???
Thanks in advance for any knowledge
Mitch
The advantage of buying engines in Canada is that the inside of the engines are pristine as anti freeze is mandatory. The car bodies on the other hand can be lace.
Fixing those rusted out studs is relatively routine at a machine shop, and as for taking out the frost plugs, well if your studs are rusted wait till you see the back of the frost plugs. Mandatory replacement of those on a rebuild. I.M.O.
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Not sure I agree with that, especially if it\they have snapped off down in the bowels of the block. Removing the stub without damaging the block thread is tricky at best. BiL’s 420G had one shear off, and he had to rethread the block oversize and make a new stepped stud.
I also don’t believe converting to a short stud is practicable as the block deck is thinner than the short stud block and will pull up when torqued. Just my opinion, but enough to make me dread pulling the head on my S1 XJ.
My personal opinion is pulling the core plugs and spraying serious penetrating fluid into the block stud joint would be optimal
It lets you evaluate the stud situation, and block coolant passages
I guess you have to ask yourself will these issues get worse over the years if left
unattended ? (hint: the evidence I have see suggest it does)
2nd I have read that various blocks can be altered, I believe Hammill discusses this in his excellent XK engine book…surely you have it ??
a must for any serious Jag nut, and the man who has everything and is hard to buy gifts for ? 
Yes cold Countries need anti freeze, and even though we dont, everyone still uses it, but towards the “end of life”: these vehicles may have poor or no maintenance and if let to sit coolant looses its anti-corrosion properties, allowing the head stud thread to gall with the female black hole and that is bad news
A good machine shop can do it of course, but they will charge a bit
Its a scary moment breaking them loose, they let go with a loud snapping sound either way, you can see the stud twisting, the breaker bar begins to flex 
I made up a set of 3 quality drill bits centred into old studs that had been narrowed down, lower down through top of block, drill up to size, heat it right up and wind out with special easy out
(this is after trying to weld a nut on which has always failed)
One time after all that trouble, I found the female thread too chewed to use the block
due to galling, not bad drilling
It gets nasty and expensive if you have a matching numbers engine, but I think they can be repaired
Otherwise you will eventually find out in the hardest and most brutal way that your head stud will not ever hold torque. The problem is hard to detect, as determining the condition of the female thread is not easy to do. ( once again, Hammill discuss this in detail, he recommends dummy head install, tighten studs, measure stud height, repeat at least once, if any stud moves up, you have a problem)
I personally dont think it would be terribly sensible to put am XJ engine in a car without replacing the core plugs, flushing the coolant passages, and inspecting the long studs
Also it should be noted that if the long studs just twist out with the acorn nuts, or any other way, then scum will fall down the hole, and make it very difficult to properly reseat the stud
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Tony,
Very nice evaluation
Thank You
Mitch
ps. I do have Des Hammill
also, Terry and Kevin…
2 things…1st I have an xk engine in pieces and the studs just came out…I need to move it and take better care of it…then of course, storing an engine for many years and not be readily able to count on it…matters
So… thank you all