28 replies to this topic

[Mini1275buggy]

It already has a rocker cover breather, but i was told that a 1275 is supposed to have a breather on the clutch housing.

[bmcecosse]

It is - but doesn't normally have one on the rocker... Does it have one on the timing cover?

[Mini1275buggy]

only on the rocker cover

[bmcecosse]

Well - it SHOULD have one on the timing case too......

[Ethel]

Thing is, if you have the breather on the rocker cover, it will just draw fresh air straight from the oil filler, and the oil will be working against the ventilation to drain back to the sump.

[Mini1275buggy]

Should it have 3 breathers?(timing case, cluch housing and rocker cover?)

Edited by Mini1275buggy, 22 October 2011 - 02:11 PM.

[Ethel]

2 -one on the clutch, one on the timing chain cover.

It needs unrestricted ventilation as a minimum to stop it blowing oil past the seals. Some suction from the inlet is better at removing the blow by fumes that would contaminate the oil. If there's only one connection on the manifold just one, of a similar size, for the crankcase will flow almost as much as two. It might not be as good at separating the oil though.

[Mini1275buggy]

ok Thanks, how can i make a breather without buying a new timing case or clutch housing?

[Ethel]

The easiest would be look for a 2nd hand timing cover. Mini covers are a bit different, to clear the radiator fan. If you you don't have a mechanical fan, or can create some extra clearance, you could use any. Alternatively, make your own to braze or screw on.

[bmcecosse]

Rocker breather does no harm - look at ANY competition Mini engine. It doesn't fight against the oil....... the more breathers the better! Leave one open if you like - as long as the other(s) are connected to the carb so it can draw away the fumes.....

Edited by bmcecosse, 22 October 2011 - 03:58 PM.

[Mini1275buggy]

Why is it so important to draw away the fumes

[benjy_18]

just a quick question, sorry to hijack.

you guys are saying that you cannot just drill a hole into the clutch housing, but what about people drilling LOADS of holes into the outer clutch cover? surley this is a bad idea aswell?

Edited by benjy_18, 22 October 2011 - 05:55 PM.

[liirge]

just a quick question, sorry to hijack.

you guys are saying that you cannot just drill a hole into the clutch housing, but what about people drilling LOADS of holes into the outer clutch cover? surley this is a bad idea aswell?

Wrong side of the transfer case, you are referring to the clutch cover, those holes are in the part where the clutch is, and must not have any oil in at all.
The side the breather goes to is where the transfer gearing lives and must have oil.

Edited by liirge, 22 October 2011 - 06:09 PM.

[Ethel]

Most competition cars don't have positive crank ventilation so the fumes will will just escape out of all holes due to expansion.

There's a few reasons to ventilate the crankcase:
Heat expansion would cause the pressure to rise and blow oil past the oils seals; the slight vacuum pulls the seals against the shafts too.
It extracts combustion products & condensation that would contaminate the oil.
The main reason for production cars is it runs the unburned hydrocarbons back through the engine and reduces emissions. That's also why competition cars don't use PCV - recirculating hot fumes leaves less room for fresh fuel 'n air, so reduces power. The effect is only minor, as there isn't much manifold vacuum to suck on the crankcase ventilation when the throttle is wide open - conversely it also means PCV wouldn't work very well on a car that's mostly driven flat out.

There's no oil where the clutch plate is, so you can drill any number of holes in the "wok" to cool it.