I guessing it really does not matter which breather setup I use? The top photo is of a late 3.4 and the bottom is an early 3.4 which I'm using.

 

Use the top one, it does a better job at keeping the oil from getting into the manifold plenum.

 

Agreed Jeff. But the coil should mount horizontally.

 

Thanks

 

On the second foto the breather is mounted the other way around.
Outlet should be on the other side, that way the Coil can also be mounted right.

 

I think there are two types of breather. The later one which came about in the mid 60s had an extra upright filter pipe and was marked on the top of the round end as "JAGUAR ENGLAND CRANKCASE DEVICE CALIFORNIA APPROVED 18 DEC 62". This is what I have on my 1967 UK S Type. A hose leads from this to the bottom of the air filter. The earlier engines and in this case the Mk1 3.4 engine would not have had this and I thought they had a pipe leading from the crankcase filter to a catch tank which had to be emptied every now and then,. Please correct me if I am wrong.
If the above is correct then I would install the breather from the late engine in the first photo but give it a good clean out with a soak of paraffin for a couple of days. Also clean the gauze behind the breather which can get gummed up.

 

Spot on!