Hi all. Thanks for having me. I’m wondering if anyone can supply me with some basic physical dimensions of a 4.2l xj6 engine? I’m currently designing a 1930s grand prix inspired car in CAD and im intending to use the 4.2 carburettored engine as they look somewhat period correct and they’re available here for cheap. The problem im having is there’s none available locally to get any measurements off, nor is there anything i can find through googling and i would like to do the design before i purchase anything. If anone can help me out I would really appreciate it!
Hi Matt welcome to the forums, I have moved your post to the XK engine section. Somebody will be able to help, its night time here but I have a 4.2 engine outside that I can measure tomorrow if no one come back earlier.
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I will point out that the 3.4, 3.8 and 4.2 are all the same physical size (exception: the Series 3 is very slightly longer due to extra water jacket at the rear). If you are pressed for space vertically, the 2.4L is significantly shorter.
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Hi Matt, The 4.2 blocks came in three versions, the original short stud block, then came the extended rear water passage with short studs, and finally the XJ6 version with long studs, extended water passages and many more core plugs on the side of the block. Be careful with the XJ6 blocks as over time the long studs, which are exposed to coolant tend to corrode and may snap off whenever the engine head is torqued. Let a knowledgeable machine shop renew all the studs. Externally they are almost the same dimensions.
Regards,
Allen
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Hi Matt…sumps are also different shape and sizes depending on what model the engine is from. …where are you located…Steve
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Thanks All. The sump isn’t a major concern as far as i can tell. This project is very loosely based around a type 35 Bugatti and theres nothing in the way to be too concerned about. Im located in Christchurch NZ. Realistically i think it will be a s1 or 2 xj6 engine as thats most likely to be available for cheap, but i’m happy to deal with issues before final commission of the vehicle. Some part of me is tempted to just run the engine as is so that it keeps the factory oil leaks as the 30s cars had 
As for the 2.4l that could certainly be an option if i find the 4.2 too tall however i haven’t seen any for sale to know what sort of price expectations they are.
I have an idea the XJ6 2.8 has a “shorter” deck height ?
I have a complete 2.8 engine/ trans, but it is not located at my place
If you can find one of them, they are normally cheaper than 4.2 as they are not very desirable, same head and carbs as a 4.2, short studs
The long stud 4.2 is an issue these days, not easy to find one without corroded studs
4.2 from 65-68 had short studs = most desirable