32 replies to this topic

[Steve220]

Hi all,

 

For my clarification, and the ever road to learning more about these engines in depth, something got me thinking. A lot of fast road/race engines have breathers on the rocker cover, however how does the crank case pressure get into the rocker cover? The only place i can think of is via the pushrod holes, but that would involve pressure getting past the followers, surely?

 

On my engine i have a 1" breather pipe from the rocker cover to a catch can in the N/S wheel arch, the timing cover breather also T's into the pipe through a 1/2" pipe.  The transfer case breather is currently open to atmosphere, which inherently has meant that oil has got over my boost pipes. I'm really limited for space for the transfer case breather as i have one of the boost pipes going right over the top.  Now, i don't really want to block this up (could I get away with blocking that?), but my concern for excess crank case pressure is there.

 

Thoughts, comments, queries?

[nicklouse]

If you are getting excessive crank pressure then your rings are gone.

 

things to think about.

 

the single vent on the cover is old skool and just helps make sure the pressure in the cover does not get too high or any air needs to go out the same way as the oil.

 

the standard set up on a mini has a vented cap and air is continuously drawn through the engine and burnt off in the engine. now of you remove this vacuum and dont replace it with say an exhaust vacuum then the engine likes to be able to move air out of the way as it rotates this is often done through big breathers to open catch tanks on race cars. on a road car that would be plumbed back to the car the same as the standard car. one thing vastly overlooked is the can on the standard breathers they are very clever when used as standard as they are actually oil condensers that pull the oil out of the vapour through the use of different diameters and wire wool. the little filters people fit are total crap and are only there to look. if you are limited for space get something made up and take it to the rocker cover if that is well vented or to a catch tank.

 

but it does kinda depend on your whole set up.

[Steve220]

If you are getting excessive crank pressure then your rings are gone.

 

things to think about.

 

the single vent on the cover is old skool and just helps make sure the pressure in the cover does not get too high or any air needs to go out the same way as the oil.

 

the standard set up on a mini has a vented cap and air is continuously drawn through the engine and burnt off in the engine. now of you remove this vacuum and dont replace it with say an exhaust vacuum then the engine likes to be able to move air out of the way as it rotates this is often done through big breathers to open catch tanks on race cars. on a road car that would be plumbed back to the car the same as the standard car. one thing vastly overlooked is the can on the standard breathers they are very clever when used as standard as they are actually oil condensers that pull the oil out of the vapour through the use of different diameters and wire wool. the little filters people fit are total crap and are only there to look. if you are limited for space get something made up and take it to the rocker cover if that is well vented or to a catch tank.

 

but it does kinda depend on your whole set up.

 

Hi Nick,

 

Not getting excessive pressure, thankfully!

 

So the rocker cover is merely a catchment area rather than a VTA on a standard car?  Understanding with the crank case having turbulant air that needs to escape, I currently have the timing cover venting nicely, the hose isn't that oily inside and the catch can only has the odd drop of moisture in it.  I think my biggest concern is the transfer case housing as this has a fair few moving parts in it too churning oil around.  I think i might look into a something custom for that as I really don't want to block it up if i can help it.  From previous experience with evos, if the crank case pressure isn't sorted, it causes the turbo oil drains to back up and start to blow seals in there too.

Edited by Steve220, 14 April 2019 - 03:56 PM.

[unburntfuelinthemorning]

Hi all,

 

For my clarification, and the ever road to learning more about these engines in depth, something got me thinking. A lot of fast road/race engines have breathers on the rocker cover, however how does the crank case pressure get into the rocker cover? The only place i can think of is via the pushrod holes, but that would involve pressure getting past the followers, surely?

Excess oil on top of the followers is able to drain to the crankcase via two openings.  One between followers two and three, the other between six and seven.  It's these openings which allow air to move between the rocker cover and the crankcase.

[Steve220]

 

Hi all,

 

For my clarification, and the ever road to learning more about these engines in depth, something got me thinking. A lot of fast road/race engines have breathers on the rocker cover, however how does the crank case pressure get into the rocker cover? The only place i can think of is via the pushrod holes, but that would involve pressure getting past the followers, surely?

Excess oil on top of the followers is able to drain to the crankcase via two openings.  One between followers two and three, the other between six and seven.  It's these openings which allow air to move between the rocker cover and the crankcase.

 

 

Aha! Brilliant! Thank you for that.

[Spider]

The key thing for a road engine with Crankcase Ventilation is that it is that and not just open vents.

 

Part of the idea of the Ventilation system is to move gases through the crankcase as best as possible to draw off all non-oil vapor from within the Crankcase, much of which is moisture and combustion by-products. If left, these contaminate the Oil grossly reducing it's life, leading to a rapid build up of acids that attack the Crank Bearings and Bores for two of the more common items, but will also eat away at many of the harder surfaces within the engine and gearbox too.

 

When the Crankcase is just open to atmosphere, some Ventilation occurs, but there's inevitably pockets where these vapors will still accumulate.

 

The other plus of a good ventilation system is that under ordinary driving conditions, it lowers the relative pressure in the Crankcase and in doing so, reduces the chance of oil leaks.

 

As it appears your engine is boosted you may want to consider a system to draw the Crankcase down through the exhaust via a scavenging set up. Might sound a little complicated, but really is very simple. Retroman put up an example (or mentioned on) in another thread recently, this may have been the set up Vizard referred to in one of his books.

[Steve220]

The key thing for a road engine with Crankcase Ventilation is that it is that and not just open vents.

 

Part of the idea of the Ventilation system is to move gases through the crankcase as best as possible to draw off all non-oil vapor from within the Crankcase, much of which is moisture and combustion by-products. If left, these contaminate the Oil grossly reducing it's life, leading to a rapid build up of acids that attack the Crank Bearings and Bores for two of the more common items, but will also eat away at many of the harder surfaces within the engine and gearbox too.

 

When the Crankcase is just open to atmosphere, some Ventilation occurs, but there's inevitably pockets where these vapors will still accumulate.

 

The other plus of a good ventilation system is that under ordinary driving conditions, it lowers the relative pressure in the Crankcase and in doing so, reduces the chance of oil leaks.

 

As it appears your engine is boosted you may want to consider a system to draw the Crankcase down through the exhaust via a scavenging set up. Might sound a little complicated, but really is very simple. Retroman put up an example (or mentioned on) in another thread recently, this may have been the set up Vizard referred to in one of his books.

 

That seems so unbelievably excessive. 

 

I'm tempted to run a PCV from the rocker cover to the inlet as you're only ever on positive manifold pressure occasionally. My previous evo's only have the PCV from the rocker cover to the inlet manifold and another (about 8mm ID) from the rocker cover to the intake pipe pre turbo.

 

My next question is why does the A series breath so heavily and yet others don't?

[DeadSquare]

 

The key thing for a road engine with Crankcase Ventilation is that it is that and not just open vents.

 

Part of the idea of the Ventilation system is to move gases through the crankcase as best as possible to draw off all non-oil vapor from within the Crankcase, much of which is moisture and combustion by-products. If left, these contaminate the Oil grossly reducing it's life, leading to a rapid build up of acids that attack the Crank Bearings and Bores for two of the more common items, but will also eat away at many of the harder surfaces within the engine and gearbox too.

 

When the Crankcase is just open to atmosphere, some Ventilation occurs, but there's inevitably pockets where these vapors will still accumulate.

 

The other plus of a good ventilation system is that under ordinary driving conditions, it lowers the relative pressure in the Crankcase and in doing so, reduces the chance of oil leaks.

 

As it appears your engine is boosted you may want to consider a system to draw the Crankcase down through the exhaust via a scavenging set up. Might sound a little complicated, but really is very simple. Retroman put up an example (or mentioned on) in another thread recently, this may have been the set up Vizard referred to in one of his books.

 

That seems so unbelievably excessive. 

 

I'm tempted to run a PCV from the rocker cover to the inlet as you're only ever on positive manifold pressure occasionally. My previous evo's only have the PCV from the rocker cover to the inlet manifold and another (about 8mm ID) from the rocker cover to the intake pipe pre turbo.

 

My next question is why does the A series breath so heavily and yet others don't?

 

 

 

The comic answer is " Because they are all talk and no go"

[DeadSquare]

The key thing for a road engine with Crankcase Ventilation is that it is that and not just open vents.

 

Part of the idea of the Ventilation system is to move gases through the crankcase as best as possible to draw off all non-oil vapor from within the Crankcase, much of which is moisture and combustion by-products. If left, these contaminate the Oil grossly reducing it's life, leading to a rapid build up of acids that attack the Crank Bearings and Bores for two of the more common items, but will also eat away at many of the harder surfaces within the engine and gearbox too.

 

When the Crankcase is just open to atmosphere, some Ventilation occurs, but there's inevitably pockets where these vapors will still accumulate.

 

The other plus of a good ventilation system is that under ordinary driving conditions, it lowers the relative pressure in the Crankcase and in doing so, reduces the chance of oil leaks.

 

As it appears your engine is boosted you may want to consider a system to draw the Crankcase down through the exhaust via a scavenging set up. Might sound a little complicated, but really is very simple. Retroman put up an example (or mentioned on) in another thread recently, this may have been the set up Vizard referred to in one of his books.

 

 

Well all that is a lovely idea, but on early A series, there was an inverted U shaped breather on one of the tappet covers that spewed it's filthy breath down the side of the engine before it ever wafted up to the rocker cover to get connected to the inlet manifold.

[DeadSquare]

Hi all,

 

For my clarification, and the ever road to learning more about these engines in depth, something got me thinking. A lot of fast road/race engines have breathers on the rocker cover, however how does the crank case pressure get into the rocker cover? The only place i can think of is via the pushrod holes, but that would involve pressure getting past the followers, surely?

 

On my engine i have a 1" breather pipe from the rocker cover to a catch can in the N/S wheel arch, the timing cover breather also T's into the pipe through a 1/2" pipe.  The transfer case breather is currently open to atmosphere, which inherently has meant that oil has got over my boost pipes. I'm really limited for space for the transfer case breather as i have one of the boost pipes going right over the top.  Now, i don't really want to block this up (could I get away with blocking that?), but my concern for excess crank case pressure is there.

 

Thoughts, comments, queries?

 

 

Early Minis didn't have a breather on the transfer case, which is open to the gear box, which is open to the cranckcase, which, as has been explained, has two vents to the tappet chest, etc:   ...  So I wouldn't worry about blocking up the transfer case breather.

[Steve220]

The key thing for a road engine with Crankcase Ventilation is that it is that and not just open vents.

Part of the idea of the Ventilation system is to move gases through the crankcase as best as possible to draw off all non-oil vapor from within the Crankcase, much of which is moisture and combustion by-products. If left, these contaminate the Oil grossly reducing it's life, leading to a rapid build up of acids that attack the Crank Bearings and Bores for two of the more common items, but will also eat away at many of the harder surfaces within the engine and gearbox too.

When the Crankcase is just open to atmosphere, some Ventilation occurs, but there's inevitably pockets where these vapors will still accumulate.

The other plus of a good ventilation system is that under ordinary driving conditions, it lowers the relative pressure in the Crankcase and in doing so, reduces the chance of oil leaks.

As it appears your engine is boosted you may want to consider a system to draw the Crankcase down through the exhaust via a scavenging set up. Might sound a little complicated, but really is very simple. Retroman put up an example (or mentioned on) in another thread recently, this may have been the set up Vizard referred to in one of his books.

That seems so unbelievably excessive.

I'm tempted to run a PCV from the rocker cover to the inlet as you're only ever on positive manifold pressure occasionally. My previous evo's only have the PCV from the rocker cover to the inlet manifold and another (about 8mm ID) from the rocker cover to the intake pipe pre turbo.

My next question is why does the A series breath so heavily and yet others don't?

The comic answer is " Because they are all talk and no go"

Lol that's brilliant! I know a few people like that too

[imack]

I'd be reluctant to block off the transfer case breather unless you can create an equal sized breather elsewhere, I don't think a timing cover breather alone is adequate. Looking at vizards book he recommends at least two 1/2" bore breathers, preferably 3 or 4 breathers on a high performance engine.

[Spider]

 

That seems so unbelievably excessive. 

 

 

That reply has me scratching my head.

 

98% of what is required for what I've suggested you already have in place.

 

There's only a pipe to weld in to the exhaust, at the right place and angle and a non-return valve to fit.

 

Fair enough if that's too complicated.

[Steve220]

That seems so unbelievably excessive.

 
That reply has me scratching my head.
 
98% of what is required for what I've suggested you already have in place.
 
There's only a pipe to weld in to the exhaust, at the right place and angle and a non-return valve to fit.
 
Fair enough if that's too complicated.

Im probably over thinking it. Essentially my issue is space.. I have little left. my transfer case vent has an alloy pipe over it with about a 2" gap from the face to the pipe. It's the one I'm most concerned about.

[1968andyf]

If your not using the mechanical fuel pump drill the blanking plate and weld in a 1/2" tube