Breathers and oil leaks

[gs.davies]

Further to the previous oil leak in LFF from the gallery plug (now fixed) I’ve got a new leak.

Engine is 1098 with a few mods - 997 profile cam, 295, CR at 9.3:1

I fitted an early 850 tappet chest cover with the downward pointing and an 850 type rocker cover which is plumbed into the air box. I’ve got quite a bit of oil dripping from the tappet chest cover.

There’s no provision anywhere else on the engine for any other breathers. Is this enough breathing? Would adding more stop the dripping of oil?

[Pete]

Replace the breather with a canister type?

[gs.davies]

I have got a canister type knocking around that I could fit. Not sure how much has got to come off to enable the fitting of it though.

Is the original breather known for simply spluttering oil everywhere?

[Exminiman]

Does it improve if you remove pipe from carb ?

Just wondering if you have an early sealed rocker cap rather than one that breathes or one that is blocked with crud

Then the only breathing would be through the tappet chest cover.....

[gs.davies]

Makes no difference if pipe between rocker and air box is connected or not. There’s no connection on the carbs for a directly connected breather, nor any provision on the inlet for a PCV valve.

The oil filler cap is a chrome type, don’t think it is vented but will check. Suppose I could run it with it off and see if that made a difference.

[Polarsilver]

Take the Carb + Manifold off & then easy job to fit a Canister type tappet cover + fit a Breather Rocker Cover Cap. my cars have as many crankcase breathers fitted as is possible all open to the air..

[mk1]

I can't remember off had, but you may be able to turn the tappet chest cover upside down so the breather is pointing up instead of down. A lot of the open breathers did point up originally.

brather.jpg

[Spider]

In my view and experience, the Crankcase Breather Set up BMC developed from the PCV system and after was one thing they got very right.

It does a few things and I'm not sure it's always understood or appreciated;-

It removes fumes and blow by from the crankcase, sends those gases in with combustion so we don't end up with a
smelly engine bay, that works it's way oh so well in to the cabin, especially when the missus is in the car.

It slightly lowers the pressure in the crankcase that can assist with oil leaks, particularly at rotating seals,

It removes moisture and other chemicals from the Oil that eventually form acids that lead sometimes to ruined
bearings but in particular, cause rusting within the crankcase, that often flakes off and does other damage.

The System is well designed and there's possibly more to it than meets the eye. The Oil Separator(s) has a large diameter inlet and a small outlet. That's important to allow them to work as oil separators as the gases entering are at a slower relative speed than those exiting. This gives the oil fumes a chance to condense and return to the sump as oil, while drawing off fumes and gases, including moisture. The system also needs a regulated fresh air inlet, usually via a vented (and filtered !) Oil Filler Cap. The Fresh Air flows through the Crankcase, picking up moisture and fumes along the way that are then drawn out via the Oil Separators.

BMC first did the System as a PCV set up, which was good, but later it was revised to a CCV (Closed Crankcase Ventilation) that worked even better.

Some may say that you loose power by fitting such systems and I would agree, however, if the engine is well built with decent rings and correct bore honing, broken in properly and maintained in good condition, I doubt you'd be able to measure a power loss, you certainly wouldn't feel it when driving. For a road car, I have always felt fitting one of these set ups is a no brainer.

[BAD942B]

can you still get the diaphragm, oil filler cap & other consumable parts for the PCV system

[BAD942B]

and how did they revise it to a CCV system

[BAD942B]

Further to the previous oil leak in LFF from the gallery plug (now fixed) I’ve got a new leak.

Engine is 1098 with a few mods - 997 profile cam, 295, CR at 9.3:1

I fitted an early 850 tappet chest cover with the downward pointing and an 850 type rocker cover which is plumbed into the air box. I’ve got quite a bit of oil dripping from the tappet chest cover.

There’s no provision anywhere else on the engine for any other breathers. Is this enough breathing? Would adding more stop the dripping of oil?

from memory the early type of tappet chest cover uses a cork gasket & the later cover uses a rubber gasket, we could never get the cork gaskets to work on the later cover & vice versa

[BAD942B]

from memory the early type of tappet chest cover uses a cork gasket & the later cover uses a rubber gasket, we could never get the cork gaskets to work on the later cover & vice versa

the concave breather type should use the rubber gasket & the convex breather type cover the cork gasket, always replace the bolt seal and use the correct metal cup

[Spider]

I have seen the diaphragms and even complete PCV Units available. I don't run that on any of my cars, so I haven't needed to go looking in recent times.

The Filler Caps are available and are a Service Item, from memory, the recommended service period for them is 12 000 miles.

The PCV System more or less relied on Manifold Vacuum. At wide open throttle, when you are most likely to have the highest crankcase pressure, there's little of no manifold vacuum and so the system is not effective under those conditions.

The Carbs were modified for the CCV System by adding a Port between the Carb Piston and Butterfly and uses air flow rate through the Carb to work, the highest flow occurs at wide open throttle, also when you'll likely have the highest crankcase pressure.

The Port on the Carbs is that one that comes off at 45 deg near the bell;-

[Peter1071]

Further to the previous oil leak in LFF from the gallery plug (now fixed) I’ve got a new leak.

Engine is 1098 with a few mods - 997 profile cam, 295, CR at 9.3:1

I fitted an early 850 tappet chest cover with the downward pointing and an 850 type rocker cover which is plumbed into the air box. I’ve got quite a bit of oil dripping from the tappet chest cover.

There’s no provision anywhere else on the engine for any other breathers. Is this enough breathing? Would adding more stop the dripping of oil?

Is the oil leaking from the tappet chest cover seal or dripping out of the breather pipe?
If it's dripping from the pipe, check to see if the rocker cover is filling with oil when the engine is running by taking off the oil filler cap. It's unlikely but worth checking! If it is then a cam bearing may have been incorrectly fitted when the engine was rebuilt.Yes, I speak from experience,

Peter

[gs.davies]

Well, I’ve got to have the carbs off tonight/tomorrow so will have a look down the back. I think it’s coming from the breather and the current plan is to fit a long breather hose and route it up and vent it through a breather filter near the radiator. I’ll double check it’s not leaking from the seal. It’s got the right seal on it as well as the right cup washer and seal on it. I’ll nip it in case it wasn’t tight.

I think I’ve got to remove the exhaust manifold to fit a canister type filter and I don’t fancy that at the moment.

The rocker cover isn’t filling with oil, just the usual amounts of oil in that place, gently oozing from between the rockers.