Visual difference in the 4.2 litre XK engines

Can anyone provide please a comparison of photographs that show and can quickly identify the following 4.2 litre engines for easy recogition?
7E for the e Type Series 1
7F for the 420
7L for the XJ6

Also was there a visual difference in the manual Moss Gearbox and Overdrive units on these three different engine installations?

I appreciate that there are internal and perhaps out of sight differences, but how do you spot what restoration work is correct at car shows?

Information I have is that series 1 E types are indeed 7E, but series 2 are 7R, Both 420G and 420 are 7D. As you say, early XJ6 4.2 are all 7L. I may be wrong here but I believe all 7E and 7D have three core plugs on LH side whereas all 7R and 7L have five.

Thanks John, that’s my understanding as well but what I’d like is actual photographs of the three engines - if 3 photos where next to each other on a table is the a noticeable visual difference at first glance (ie: cam covers, HT lead layout, air filter, etc). I’ve noticed when people restore these cars they sometimes get mixed up or are mis sold engines. An ‘idiots guide’ by photo recognition might be very useful tool for us Jag lovers. Obviously original and unrestored engine bay pictures would be more acturate to look at as I’m sure many people often add extras or changes when restoration takes place.

Hi David…it gets a bit complicated when you say “engine”…the block has the number stamped on it and is the only way as far as im aware to be 100% sure what you have. …sumps, heads, ect can all be swapped over as you know…so the “idiots guide” is check the engine number and that it matches the V5 (registration docs)…Steve

Yes I agree the only sure way is to check the serial numbers, but not everyone will have a flashlight or can crawl under a car to view the numbers (often in my experience covered over with paint and dirt, and that’s when you know where the numbers should be!!). Opening the bonnet (hood) and seeing what the 4.2 engine should visually look like at first sight would for me be the first starting point of knowing if it is right for this Jaguar model or a substitute. If it looks wrong then it probably is wrong when you delve further into Registration Documents, etc. If all these engines specifically look the same from a quick visual check point then my belief that I’ve seen in the past physical differences (like ribbed or smooth engine covers, different positions of HT parts, etc) might be just a dream or what restoration changes have put in.

Ok So your just interested in the basics of what the 3 models look like when you lift the bonnet… however there are many differences in the various models depending on if they are UK or export models…google is your friend lots of info and photos…E types never had overdrive and Xj6 dudnt have a miss bix…it had 4 syncto with compact A o/d… Steve 67 420

S1 E type
Xj6 S1

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Thanks for these pictures Steve. The problem I’ve found with Google searches (and perhaps with your nice photos) is are these original specs or upgraded in restoration?

Here is a 420 engine I photographed, claimed to be original, and certainly has the 7F serial number as I inspected the stamping on the block myself. Obviously the HT leads, spark plugs, rubber hoses, etc will have been changed - but the 2 engine covers are ribbed, the air filter is a plain box, etc.

So has anyone any old Jaguar factory photos please of these 3 engine types and did the factory mix and match what they had in stock or vary with year of manufacture, or upgrade fitment options (like my MK IV SE 1.5 has features and parts normally found on the bigger 3.5 litre, as it was the luxury Special Equipment version, complete with heater and chrome bits).

The blocks had part numbers - not only the engine numbers. So if you you really want to differentiate you need to be more specific. Do you mean the engine as such (complete with head and carbs) or just the block? Then you might want to ask as to for which market the engine was produced.

Well if thay said the engine is original and you checked the number then it is…but as stated before other things can be changed…yes some 420 had smooth cam coveres some had ribbed…none as far as im aware had those carbs… they all had HD8,s…air filter looks wrong inlet manifold? for factory photos as mentioned befor yoy have different specs for different markets…UK/US/ Europe…Im affraid what your asking is too simplistic…you need to reasearch each model and understand the changes that were made through production…Steve


An (late S1?) S2 XJ inlet manifold and carbs and a head that has been painted by a 5 year old. Mixed acorn nuts new & old. Do I see a later (70s) power steering reservoir cap. Doesn’t matter, it’s not original.

David please be more specific. You need the block numbers, either they match or they don’t, you couldn’t tell apart from long/short stud, frost plugs etc.

Thanks everyone for the information and feedback. I guess the short answer is things are not always what they appear or you are told!! I need to improve my knowledge of these 4.2 engines and teach myself how to spot the correct and none genunine engine bay parts.

Usual giveaways are carbs, lifting brackets, nuts and ignition wiring, but not necessarily - and a head or engine swap does not make it a bad engine, just less original!

Look on the old site for the model brochure section and year you want to check. For anything US the Coventry Foundation hass brochures?

I had a North American 420 engine. It had the same ribbed cam covers. The early ribbed cam covers lacked a fillet near the center for clearance for the exhaust heat crossover (see photo of the red car, above) and also had the Jaguar logo cast in the intake side. Later covers had a Jaguar (or Daimler as appropriate) sticker or decal. No doubt other differences. I would opine that those cam covers would be appropriate for a North American 420.

The cam covers are original, at least not from the car that donated other parts like the intake manifold.
The distributor is early too, but I’m not familiar with the XJ S2 ignition. I think that switched to electronic and lost the vernier screw?

Looks like the acorn nuts that have been replaced have no washers. Whoever does such a thing, I’d wish I could kick them. They did the same on my engine.

What is always easy to tell is if something was done and if it has been done well. This has absolutely not been done well, sad to see but not hard to fix… hopefully

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David in the USA but nowhere else the S2 got EFI and electronic ignition at the end just before S3 arrived. I think they are covered in the Haynes manual and initially the ignition was not CEI

Thank you everyone for those helpful points and information.