Engine breather filter

The club sell them.

Gaskets especially cork usually dry out and SHRINK.

High crankcase pressure does not cause high oil pressure - blocked oilways in V8's do though as even a sticking relief valve is very unlikely to do this with a standard V8 pump.

The cork gasket can easily become displaced - check it again. Are the gauze flame traps clear AND the tubes especially those in the carb bodies

Thanks Phil and Crossplies. My old (and new) rocker gaskets are rubber. When I took the old one out it looked completely the wrong size. Anyway, with the new one in, no smoke after a half hour on the highway. I can't describe the amount of smoke prior - it looked like a blown engine.
Crossplies, I've put in a 'universal fuel filter' in place of the old engine breather filter. In my 'Owner's Maintenance Manual' it says 'Fit the filter with the end marked 'IN' uppermost. Alternatively, if the filter is marked with arrows, they must point downwards.'
The old filter had an arrow pointing upwards to the bonnet. I've put the new fuel filter in with the arrow pointing down to the ground. Now I don't know which is right. Is the air coming OUT of the crankcase or INTO the crankcase? Is the information in the Owners Maintenance Manual wrong, or was the original filter different?

Thanks Crossplies. I've checked the WSM vs. the 'Rover 3 1/2 Litre Owner's Maintenance Manual' and the wording is exactly opposite in each. WSM says the 'IN' of the filter goes down, Owner's Manual says up.
Your explanation makes sense. I presume you need to filter any oil out of the crankcase gases before they go through the carbs. I'll reverse my filter so the arrow goes up.

I think I detect a bit of confusion here, so I'll chuck in my two bobs worth.
I'll set this out in point form just in case we're all talking about different things and I've got the wrong end of the stick.

In the days before air pollution concerns, the crankcase was naturally ventilated.
Typically the oil filler cap screwed into the rocker cover and the cap included a vent.
Sometimes that vent even had a forward-facing scoop to push air into the rocker area and down into the crankcase.
There was a vent pipe of perhaps 1/2" to 3/4" in diameter attached to the engine and it extended down towards the road. It came from (typically) the pushrod cover on an in-line engine or perhaps the valley cover on a V8.
Fresh air went in through the filler cap vent and all the oily fumes came out the vent pipe and away under the car.

Then positive crankcase ventilation (PCV) was introduced.
Initially this was done by removing the vent pipe and fitting a rubber tube with a one-way valve (PCV valve) back to a connection on the carby. These were also available as aftermarket kits.

On the Rover V8 the crankcase fumes are drawn out of each rocker cover, through a flame trap, and into each SU via the familiar semi-rigid rubber hoses.

The flame trap is the small grey metal capsule that sits in the middle of each set of hoses.

The flame trap's function is to prevent a flame that may be present in the carby, perhaps due to a backfire, from igniting the oil (and sometimes fuel) vapour that exists in the crankcase.

If this occurred the flame could flash back into the crankcase and perhaps do unpleasant things.

The flame trap contains steel wire gauze and it works simply by extracting the heat from a passing flame and thereby extinguishing it. (Like the old Davey miner's lamp).

The gauze is not intended to act as a fume filter - it can't, it's too coarse. But it does tend to accumulate oily crud and can become blocked or restricted. This will limit crankcase ventilation.

You can clean then by swilling them out with kero (paraffin) or petrol.

If you can see right through them, then the gauze has rusted away and they will no longer work as a flame trap.

They are still available because Range Rovers used them prior to EFI being introduced.

As the SU applies suction to the crankcase atmosphere via the flame trap, fresh air has to be allowed in somewhere otherwise ventilation and fume removal can't occur.

Fresh air enters via the rear of the block through the rubber tube that connects to the rear of the air-cleaner body (the oval part).

It could have simply been left to draw air from the engine bay, but Rover chose to attach it to the air-cleaner body.

Therefore it had to be connected to the centre section of the oval body before the air-cleaner elements (filters).

If it was connected after the filters it would be subject to a partial vacuum.

Therefore, where it connects to the air-cleaner body it receives unfiltered air.

Therefore dust would be drawn down into the crankcase.

To solve this problem they fitted a small fuel-type filter in the rubber hose.

The path of the ventilating air is ... into the air-cleaner intake, out the back of the body before the air-cleaner elements, through the rubber hose and in-line fuel-type filter, into the crankcase, up through the oil drain passageways into the rocker covers, and along the larger rubber hoses and flame traps into the SUs to be burnt.

Therefore the flow of air through Michael's filter is downwards towards the road.

If an in-line fuel filter is used for this purpose, I can't see any reason why the marked direction matters.

The flow direction is important when filtering fuel because the device is designed to have a space near the inlet to collect any water in the fuel.

They also filter on the outside of the paper element so that you can see the accumulating particles - except of course when the manufacturer starts using opaque plastic so you can't inspect it and determine that it doesn't need replacing yet!

When used as an air filter it will work equally well in both directions.
But if you have a transparent one, using it the correct way around will enbale you to see when it is dirty.

If the flame traps become clogged, fumes could be forced back up the inlet breather and clog up the paper element of the inlet filter.

If the original Rover part incorporated a non-return valve like the early PCV valves, then mounting it the right way around is very important.

But if the original Rover part was also just a petrol filter with the standard inlet or flow direction markings, perhaps Rover specified a fitting direction so that people didn't become confused when they found marking on them.

Rover Car Service News Letter dated August 1970 admits that the original information was incorrect. It also confirms the correct fitment to be with the end marked "in" uppermost, or if marked with an arrow, the arrow must point downwards.

Warwick, many thanks for your typically logical and crystal clear post. I now claim the record for the most frequently rotated P5B engine breather filter in history. Acknowledging that it may not matter which way the arrow points, I will reverse it yet again, in what I shall always think of as the Warwick/Crossplies duality. I think we are now in agreement - the Arrow should point Down Under. How apt.

Warwick:

No data on OE filter, but the units available currently do not seem to have any form of bias to airflow, its just as easy to suck or blow thru either end!

Thanks Michael.
Could I have that in writing please, so I can show it to my wife?
Doh! It is in writing. All I have to do is show her this thread.

Perhaps on second thoughts - then she'll find out how I spend my lunchtimes ... and various other times. Best leave well enough alone.


Take note of what Phil said at the top of the page. It will all depend on how long it has been pointing the other way and if you would expect much dirt in it. (i.e. where have you been driving it)

I should one day post a photo of my 'workshop/garage' wherein sits the Rover and my wife's 1992 Mazda 121. On the old dining room table that is now the 'workbench' are half a dozen spanners, some screwdrivers that have suffered by occasional use as chisels, a multimeter that remains a mystery to me, and some pliers whose ends don't quite meet. A Gunsons carb balancer and tuning plug are recent high tech additions. An oily exercise book is used to note every stage of every operation performed, so that reversing the procedure is less of a lottery.
This forum, with the quality of advice and experience on offer, has allowed me, a complete non mechanic, to keep this car on the road for the last half dozen years. The best posts should be bound in leather and reverently handed down to future generations.
I will take Phil's advice and not re-rotate the filter. I've have lavished $4 on a new one. The old one will sit alongside my now replaced fuel sender and mechanical fuel pump, reminders of successful threads on this forum.

That should be connected to the hot air riser from the exhaust manifold for the AED if you have one, if not it should be blocked, or the elbow changed to one without the pipe as it will draw unfiltered air into the carbs.