Two oil-filler/breathers. Why are they there?

[Alan Drover]

Definitely a breather outlet is not needed on a 2.5. Didn't realise that's what it was for.

[island dormy]

  I modified my 62 to work as a modern car does with a PCV valve, I got tired (and so did SWMBO) of smelling like exhaust every time we went out in the rover.
 I sealed the narrow vents on both caps, added a elbow near the bottom of the tall oil filler tube that then went up to an American style (small in line) 4 cylinder PCV valve then across the top of the valve cover over to the bottom of the carb inlet (silver pipe 1/4 inch) where the vacuum sucks the blowby fumes from the crankcase back into the engine to get reburned again.
  The original breather on top of the valve cover (with the vent now sealed off) got a nipple attached to it which goes via a 3/8ths black rubber hose into the large metal elbow that attaches to the top of the carb.
 It works great and no more fumes in the cab. Of course I might have lost 1-2 HP by doing this, as the engine is now burning fumes with out much oxygen, car companies in the 60s fought tooth and nail against adding this pollution control measure.

  Victor

[Alan Drover]

2.5 petrol engines didn't have an oil filler cap on the rocker cover as the breather cap doubled up as an oil filler. I fitted a 2.3 5mb rocker cover to my 2.5 as it has a separate V8 style oil filler cap.
The rocker cover is ERC2866.. Blanchard's list the price as £88.54 but they're out of stock. Another retailer has them at £195.00!!!!!
The correct rocker cover for the 2.5 petrol is ETC5955. Craddock's list them as a substitute for ERC2866. 
The price is an eye watering £492.50 including VAT.

[NoBeardNoTopKnot]

Yes, I looked at those prices - made no sense. What I want is better achieved for £30odd and have it done.

I like the idea of making a proper PCV. Done right, lowering crankcase pressure may well give some, emphasis on 'some' gains into the bargain. PVC on the other hand, is summint kinky...

Racers put vacuum pumps on c/cases.

[Alan Drover]

I remember now that I've got a spare ERC2866 and filler cap somewhere in the garage.

[NoBeardNoTopKnot]

Two days ago I'd be ready to bite you hand off for that - reckon any S2/S3 filler pipe - for getting oil in the thing - will do what's required. If I hadn't gone with the pipe now I'd still have your part.

Still not sure why I need the spacer, I'm hoping it  becomes apparent when I fit.

[Alan Drover]

I'm now wondering what I did with the ETC5955 rocker cover that I took off the 2.5.

[island dormy]

  The spacer is to stop oil being sucked up the tube (as already stated) it is also a flame trap if a back fire makes it all the way through into the crankcase it might stop the fumes from igniting.

  Victor

  You'll also need to purchase or make two paper gaskets.

[Alan Drover]

It seems I don't have a spare ERC2866 as I had a good look for it but can't find it anywhere. It probably got thrown out in a clearout I had some time ago.

[NoBeardNoTopKnot]

A flame-trap, of course. Shame about the 2.25 rocker-cover. No matter to do all I want, get oil easily, the pipe will do. Thanks to  you both,parts have arrived, I'll throw the lot on this w/e.