Crankcase breathing

[PulpitNeil]

Hi there,

I have been reading over the forums and it seems that alot of people suggest that running a pipe from the rocker cover breather to the carburettor (rather than to the air filter) helps with crankcase pressure, and therefore oil leaks.

My newbie question is thus: How the heck do you do that? I see nowhere on the carb for the pipe to connect to.

Apologies in advance if I'm being monumentally stupid.

[Declan_Burns]

Neil,
Not all carbs had the connection. You could drill and tap the inlet manifold or easier the carb spacer but remove it and clean off any swarf. Many have it connected to the air filter but it is supposed to clog up the paper element.
Regards
Declan

[PulpitNeil]

Mine is currently connected to the air filter, and yes, it gets splattered and clogged very quickly. I also have a slow oil leak which I imagine better breathing would cure. Do you have a photo or diagram of where I need to drill?

[Declan_Burns]

Neil,
Here's two photos of a tapping point on the carb spacer.This was actually a connection for a brake servo but the principle is the same.You dont even have to tap, you can just use a piece of brass tube glued in with epoxy.[frame][/frame][frame][/frame]
Regards
Declan

[bmcecosse]

If you do that - you will need to limit the 'suck' by only having a 2mm hole for the fumes to go through - and even then - it WILL upset the idle. But for a smoky engine it works well. It is possible to make a hole in the front face of the aluminium casting that bolts to the carb - and to which the air filter casing fits. The tube from the rocker cover goes in the hole, and the fumes are thus drawn nicely away without splattering the paper filter. Alternatively - get the later HS2 carb which has the little brass tube on the side to take the fumes.

[mike.perry]

It should be possible to buy a spacer with a breather tube, I have one in my box of bits.

[bmcecosse]

The breather tube in the spacer is just a vacuum take-off for the dizzy advance.

[Declan_Burns]

Minispares sell them
http://www.minispares.com/Product.aspx? ... 394&title=

Regards
Declan

[PulpitNeil]

If you do that - you will need to limit the 'suck' by only having a 2mm hole for the fumes to go through - and even then - it WILL upset the idle.

Would doing this make it impossible to get the idle back to normal by adjusting the mixture and idle speed? My engine isn't smoky at all, just drips oil and splatters the air filter.

It is possible to make a hole in the front face of the aluminium casting that bolts to the carb - and to which the air filter casing fits. The tube from the rocker cover goes in the hole, and the fumes are thus drawn nicely away without splattering the paper filter.

And this doesn't upset the idle? Could you explain where exactly the hole goes? Novice here!

Looking at my carb, there seems to be a small blanking disc just under the inlet for the distributor vacuum advance. You can actually see it in Declan's picture too. Would this be a good place to tap?

[bmcecosse]

The hole in the mounting plate won't upset idle because it is before the throttle plate - just avoids the air filter element. Drill/tap the carb at your risk. It may work - and if it doesn't, I guess you can just plug the hole.

[chickenjohn]

If your traveller is a late car, it may have originally had the "mushroom" breather/emmissions valve arrangement on the inlet manifold. My traveller has one of these- and amazingly new diaphragms are available. Traveller would not idle properly with the old leaky diaphragm.
Let us see a pic of the area please?

[mike.perry]

[frame][/frame][frame][/frame]
Is this what you mean? I have just stripped it down and cleaned half a pint of mayonnaise out of it. Maybe the engine will not drip quite so much oil

[bmcecosse]

IF it's all clear - it works quite well.

[dellerie]

i have an alloy rocker cover to go on my engine, only snag is that it doesn't have anywhere for the breather pipe to connect to.

will this prove to be a problem for crankcase breathing?

[mike.perry]

It depends what engine, 803-1098 vent through the rocker box and tappet chest, 1275 vent through the timing chain cover

[bmcecosse]

Either add a vent to it - or get rid of it. I've never understood the fascination for these alloy rocker covers - no performance advantage, and they are actually heavier than the original, and no breather !!

[dellerie]

It depends what engine, 803-1098 vent through the rocker box and tappet chest, 1275 vent through the timing chain cover

its a 948.

[chickenjohn]

[frame][/frame][frame][/frame]
Is this what you mean? I have just stripped it down and cleaned half a pint of mayonnaise out of it. Maybe the engine will not drip quite so much oil

Yes! That is the mushroom breather. If you're having idling problems, get a new plastic diaphragm for it:-

My traveller idled too high until I got a new diaphragm in the breather and after that no problems at all.

http://morrisminorspares.co.uk/shop/pro ... 58626dfe0b

or from one of the other suppliers as well.....

You would also be better off with a vented oil filler cap- as present in the standard rocker cover. I don't know if you can get one for the fancy alloy rocker cover you have there.

[mike.perry]

The rocker box in the photos has a breather vent and a flip top oil filler. Besides it only cost me two quid at a national rally- and I like it! Perhaps someone could tell me the make.

[chickenjohn]

Well, if it breathes, then it should be OK. Just make sure the diaphragm is OK and the rest of the breather system is unblocked.