So the recently purchased 84 and 85 are both supposed to be 4.2's but neither have any obvious indication of engine size and both titles don't list either?
How to you identify the engine size? the VIN decoder on here didn't help.

 

Easiest way: The 3.4 engine had twin carburetors rather than fuel injection....and the 3.4 Series III cars never sold into the USA.

However, I'm pretty sure that all XK type engines had the displacement cast into the side of the block....possibly obscured behind 'stuff'

Cheers
DD

 

If the cars are fuel injected they are 4.2 litre engines. As Doug says the rare 3.4s always used carburetors.

 

Every six cylinder Series III (and, for that matter, I and II as well) sold in the US and Canada had the 4.2 litre engine. In Canada the Series I, II and III cars were sold also with the V12 (5.3 litre) engine - in the US only the Series I and II had this engine.
So unless your cars were not US-market cars originally, they both have the 4.2 litre engines - but to verify: the 4.2 Series III car is fuel injected. The 3.4 litre engine as sold in some other markets always used carburetors.

 

Thanks guys, both are US spec fuel injected cars.