breather pipe

[a8pte]

please can someone advise me about the breather pipe on top of the rocker.we have changed the 10.98 to a 12.75 midget and when i travel its blowing a lot of oil out through the side breather pipe which is facing down so its making a lot of mess as you can imagine.any suggestions please would be appreciated..

[bmcecosse]

The top pipe must be connected to the intake system in some way - to suck away and burn the carcinogenic fumes. Best of all is to the side inlet pipe on later carbs. How do you have a side pipe ?? The 1275 does not have that possibility.......since there are no cam follower chest covers.

[a8pte]

got a breather pipe coming from the timing chain cover facing down at the side of the engine (12.75)

[bmcecosse]

Ahh right. So I'm afraid that indicates considerable blow-by at the piston rings..... ie A well worn engine.

[a8pte]

ok many thanks now i know

[mike.perry]

There should be a canister on the front of the timing chain cover with a pipe pointing upwards. This should be connected to the carbs with a hose

[bmcecosse]

Not if the rocker cover has already been so connected......

[IslipMinor]

On a 1275 the oil separator on the timing cover is connected to the carburettor vent intake. The 1275 never had a connection from the rocker cover, which suggests that the rocker cover is not the original from the 1275 engine.

Do you have some pictures of the engine so that we can see what there is in place and connected to what? What carburettor are you using? Which oil filler cap does it have, vented or non-vented?

[a8pte]

using same timing chain cover but cut the cannister off as it was hitting the fan.so we just welded a small metal pipe in its place and then fitted a long rubber pipe off it and ran it from the timing cover to the side of the engine.every time i use the car it blows engine oil out .so using loads of oil.not sure if the long rubber pipe should be facing up or downwards.any suggestions would be much appreciated thanks....

[bmcecosse]

Ahhhhhhh - the canister is there to separate the liquid oil from the fume. By removing it - you may now be simply blowing neat oil out the pipe - although of course there must be 'pressure' there to do that - and there should not be any pressure if the rocker cover breather is doing it's job. I'm a GREAT fan of the rocker cover breather - but you will see that Richard is not.... Has always worked well on all my A series engine. However - I do think you should refit the canister and see if that works. You can either neatly cut a slice off it, and weld on a flat strip of steel - or simply space the fan forwards slighty - or indeed remove the fan entirely. For a trial - you could run your pipe up into a small tank (catch tank as used for racing etc) and then run a vent away from the tank, and see if that is any better/any less oil used. Which check for engine condition - with it hot and idling - rem ove the oil filler cap and rev up. Is there a plume of smoke/fume??

[a8pte]

many thanks now i must get a cannister as i threw old one...

[bmcecosse]

Do the simple trials first..... The other possibility is that you can use the mechanical fuel pump opening as a breather connection - but again, build in an oil separator in the vertical run up from the opening.

[a8pte]

very helpfull thanks .....

[IslipMinor]

I'm a GREAT fan of the rocker cover breather - but you will see that Richard is not

It's not a question of being a 'fan' or otherwise. The rocker cover has no oil separator and was never used as part of an original closed circuit beathing system design, which all the in-line 1275's, at least, had as standard. It may work, that is a completely different matter, but it was never designed that way.

I have had various experiences with our 1380, which are not noted for good ring sealing properties. When fitting a timing belt conversion for a while, which had a very restricted connection from the timing cover, but NO oil separator, to the HIF6 carburettor, we suffered from more weeps and leaks from the rear crankshaft scroll than before. Oil consumption increased from ~1,000 miles per litre to <200! The leaks have more or less disappeared, now that I have reverted to a standard duplex chain and 1275 timing cover with the oil separation canister, and the oil consumption has also reverted to the previous 1,000 per litre. Yes, it is another sample of one, which are notoriously statistically unreliable, but rather like restoring the by-pass hose, but it has worked very well, so I will settle for that!

[bmcecosse]

Oh indeed - but the rocker cover breather does have a flap of steel across the inlet to prevent any direct oil ingress - and there shouldn't be all that much oil splashing about in the rocker area anyway. It is very important to have some suction on the crankcase - how this is achieved depends on personal whim. I very much dislike the 'leaky cap' breather - mainly because I believe when working hard , any engine is likely to overcome the breathers and to expel some fume. I prefer this to happen via a breather that is exiting under the car -away from my breathing zone ! But as ever - each to their own.

[mike.perry]

I'm with Richard on this one. The 1275 engine requires a negative crankcase pressure to prevent rear oil drips, therefore the pressure must be physically sucked from the sump. Ventilation is not sufficient. On smaller engines with tappet chests there is sufficient clearance past the tappets and push rods to allow the pressure to escape into the rocker box and then into the air filter. The 1275 lacks this clearance which is why pressure builds up in the sump. This can be illustrated by pouring oil into the engine, on the smaller engines the oil will quickly disappear into the sump, on the 1275 it will trickle slowly from the rocker box

[bmcecosse]

ALL the engines need suction - no doubts about that. The 1275 engines have PLENTY of passages in the cam follower area to let fumes up the pushrod holes in the head and on into the rocker cover for extraction there.