I have a 71 ser 3 e type that had droped a valve seat. I pulled the motor and rebuilt it completely. I also changed to EFI from a 86 XJS donor car. I purchased instruction from AJ6 Engineering out of England. The instructions are complete and you should not have any problem flowing them. I am a old school carburettor guy and never worked on fuel injection cars but my v12 runs just fine.
Common and popular swap with the XJS V12 guys.
More frequently the 700R4 trans is usedā¦which is the earlier, non-electric version of the 4L60E. Not sure if swapping into an XKE presents any unusual problems.
If predicted usage includes running right up to the 6500 RPM redline then the 700/4L60 will need some upgrades to survive.
Cheers
DD
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Nothing wrong with the stock Zeniths, particularly on the simpler 1971-1972 cars. Simply add the adjustable needles from later cars and install optimized needles. We were doing that in the mid-1970s. I have an early 1972 that I purchased new, did that and several other minor mods and ran the car in track events at Riverside, Ontario, and Willow Springs in the 1970s in club events. The Zeniths were never the limiting factor, even on the 9:1 early cars. The Zeniths were not even the limiting factor on my XJ-12 Series 1 with 10.5:1 compression. That car did 1:33s on the short course on RIR with the BW.
I have a V-12 with the SU conversion in the shop right now and all of us are wondering WHY anyone would do this even with the parts available for free. I had a service manager that converted his E S3 to Jaguar FI in the 1980s and it only gained easier starting when cold.
Sure the 4 speed auto in the 6.0 cars was an improvement, but if you really want to throw that much money at the car, the longer stroke 6.0 engine is THE worthwhile improvement.
Probably makes no sense to pull engine and trans for oil leaks as it is unlikely the points that leak require that. Front pump seal? We have done dozen on engine out/in work on E S3 but for oil leaks? I put 602K miles on my ES3, XJ12 S1, and 79 XJS.
FWIW, here is a pic of me with an E S3 engine out taken 52 years ago
You had to remove an engine in 1971? There must be a story behind that.
I canāt recall if there was a reason it HAD to come out as I liked taking things apart. I literally ended up in the Jaguar business as I couldnāt stop playing with cars long enough to get a ārealā job. It was the first E S3 delivered by the local dealer and was being driven a lot by its owner. It likely was a year old at the time but had enough miles to be out of warranty. That was our project car to figure out a way to make an E S3 run cool in this hot climate so had probably run too-hot too-much by that time. The owner had an XK-140, XK-150, MkII, and that car, adding a new 1977 XJ-12 so I spent a lot of time working on his cars.
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Totally understand!
My former mechanic told me heād have to take it out to reseal both the engine and trans. He said he would āpingā the valve seats to keep them from dropping (he said Jag V12s were prone to this problem.). He said heād R&R whatever else was amiss. He mentioned $20k just to do this bit.
He says he does not do EFI conversions which is what got me looking. It seems sealing the engine and trans at the same time as doing an EFI would cut overall costs and allow any other engine issues to be addressed.
I have been quoted $25k to do it all by a shop in TX. By contrast a shop in OR quoted $75k.
It seems that improving the auto trans to a 4 or 5 speed at the same time as the above makes sense. GM or ZF? I canāt seem to find a committed answer.
RSVP!
In order to get a Jaguar V-12 to drop a valve seat, the engine needs to be severely overheated in that area, generally the left rear quadrant. This is much less likely on an E-Type than on a later car. The ignition amplifier, before they moved it on top of the radiator about 1978, would turn the ignition off before you could get cylinder heads that hot. Out of dozens of dropped valve seats we have fixed over the decades, virtually none of them have been E S3 cars.
HUGE difference between replacing gaskets for leak repair and removing cylinder heads to peen valve seats in heads.
Iām trying to wrap my head around any reason for a shop to be quoting prices for a customer in another state calling about theoretical work, particularly in a state that doesnāt have a Bureau of Automotive Repair like CA.
Can anyone show me a completed E S3 with a different auto trans that is successful? Running, driving car with a satisfied customer. I have a $1M inventory of new Jaguar parts, mostly E-type, and talk to shops all day long. Iāve never heard of one.
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TY for that insight. As I said, I am stuck in SOCAL with no shop nearby.
With the torque of the V12, you never need to approach red line. I m heavy footed but never shift over 4000, maybe 4500 onve in a while. No need to.
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Interestingly, enough, itās about the same for the six-cylinder: I always pretty much shifted about 3500 to 4000.
Both engines make beautiful noise at 5000 RPM and up, but if anything goes wrongā¦
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My E S3 worked very well with the BW Model 12. It had the early US 9:1 compression, adjustable metering needles with correct needles, and converted to vac advance with a correctly drilled carb orifice. Tuned on a dyno, or course.
I converted my fatherās 73 XJ12 to 10.5:1 compression and the same carb & ignition mods and it was fine. Broad torque curve and reasonable weight compensated for a trans that wasnāt ideal. That is why I converted my E S3 to a manual trans 35 years ago but I sold the 73 XJ-12 with 292K miles on it.
THE solution on these cars is compression ratio and proper adjustments. A stock US spec 1973-74 car with an auto trans is not reasonable.
That isnāt to say that the later 6.0 with the increased stroke and improved trans isnāt the car Jaguar should have built all along. 90x70mm cylinder dimensions is a bit silly on the 5.3 when you look at 365GTB4 at the same time being 81x71mm with 4 cams and 6x2bbl webers.
4500RPM?
Whereās the fun in that ? 
I forgot what list Iām on. If youāre in a V12 XKE the engine will feel very torquey. My experience is in the XJSs and sedans. Over 4000 pounds with a 2.88 differential so the power of the engine is a bitā¦stunted. If you donāt wring out every ounce of power the Honda Accords and Toyota SUVs will trample you to death!
When I had a 4.2 I didnāt take it over 4500. It never sounded happy. Respect for old machinery and all that. And, really, there isnāt much if any advantage power-wise, it seems.
I have no qualms with the V12, though !
Cheers
DD
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Itās kind of the bottom line.