valve chest breather/diagnosis of contributing issues

[JonE]

First time ever I've had fumes from here - on a clean three bearing. Thought it was exhaust but it wasn't.
Standard late Austin arrangemements.
I was going to put on an alloy plate with no breather holes on another engine.

Are there any disadvantages?

and is there any reason why I might be getting fumes from here, over other engines?

[Robert Leigh]

Without breather holes the engine can't breathe and it will try to blow any piston leakage trough the main bearings. Any blow-by on the pistons has to go somewhere, usually through the valve chest and cover. For that reason your alloy cover does need holes. The amount of blow-by usually depends on the state of the pistons and bores.

[leaf200]

I had a saloon that had a lot of fumes on the valve breather so a blocked the holes and added a pipe from the breather to the external of the car.

[Howard Wright]

Hi Jon

I second Leaf’s comments.  Many cars ran a breather back into the air intake. That at least stopped the smoke trail!

Cheers

Howard

[JonE]

ok thankyou all. I thought this was reasonably recently restored in road miles, but it was 1955! And I didn't strip the (newish) pistons when cleaning it out. Could it be that these things improve if its only done lots of short runs so far?
I think things are compounded by the Woodie have scuttle ending abruptly and then there being gaps and wood... all comes up through the passenger's feet. So I'll sort out a breather. Does it ideally want to go with gravity or just anywhere where there is "pull" for the airflow?
1/2" tube enough?

[David Stepney]

My RP produces fumes from the holes in the tappet cover, especially when climbing steep hills, when the engine is working hard and the oil gets nice and hot. The faintest of blue miasmas appear in the front passenger footwell together with a distinct smell of hot motor oil. All three sevens that I have owned did this (the special only with the hood up), so I have presumed that it is one of the quirks of design.

[Andy Bennett]

I blocked the 4 breathers then added a half inch flexible plumbing pipe attached with plumbing connectors routed down parallel to the exhaust so it quietly puffs away under the car and pushes out to the passenger door rather than towards the gearbox gap.

a bit longer than this one:

https://www.screwfix.com/p/flexible-copp...lsrc=aw.ds

[JonE]

would an old speedo outer be up to the job? Was just noticing them all earlier today, ironically...

[Graham Barker]

I have a 1937/38 Ruby with a pressed steel tappet cover. This does not have any breather holes. I am having a problem with oil being splashed out of the filler cap. It is difficult to believe that the splashing in the sump could send oil all the way up to the filler cap. Perhaps blow-by is wanting to exit through the filler cap and carrying oil up there.
Does anyone have experience to help confirm that blow-by is causing the oil spilling? Also, should there be some other form of breather for the blow-by On this engine?
Graham Barker

[JonE]

Thankyou to Steve Jones for this idea - drilling out a bolt to put a rubber hose onto - saved me £2.80 for a plumbing fitting.
Tested this with rubber hose to outside wing, and it worked... puffing out occasionally like a super tiny exhaust when under load.

Will be even better if I had remembered to block the 4 original breather holes up before tightening it all up again.

I realise this is all short term stuff and will check valve stems and piston rings when I eventually take engine out to do the noisy release bearing. But it feels strong and loose.