Morris Minor Owners Club

You need a Marina manifold to fit the HS4 or HIF carb and a 1275 exhaust to fit the Marina manifold

I can never understand why they eliminated it

All external vents were eliminated when the closed circuit breathing system was introduced on the later 1098 and all in-line 1275's (probably on Mini's as well?). The first system used the inlet manifold mounted PCV and on Midgets the later 1275's used a port on the HS SU in a similar way to the HIF range of SU carbs. Apart from keeping everything cleaner, it also helps to keep more oil inside the engine with the partial vacuum in the crankcase.

Some put a 1" diameter breather into the rocker - for competition use.

Competition is entirely different - Webers have no vent facility and in the competition heyday it was the HS range of SU's that were used and they have no vent port (apart from the late 1275 Midget SU's, which did). For competition ventilation it was all about open vents, tubes and catch tanks (which need draining regularly) - not the same thing at all.

The choice is simple, use an open system and let the oily fumes exhaust to atmosphere (helps to keep the underside of the car and possibly engine bay nice and rust free with the oily coating), or use the later closed circuit system and keep the oil and fumes inside the engine, with the advantage of the partial vacuum helping to keep more oil inside the engine.

No! The Minis were always kept open - large breather on the transfer case on 1275 versions. The 'closed circuit' may have been fine when the engines were new......but with a bit of wear - there WILL be leaks unless you breathe the engine.........

The Minis were always kept open - large breather on the transfer case on 1275 versions

I don't know about Mini's. Are you saying that all production Mini's had an open crankcase ventilation system and none were fitted with the PCV or carburettor ported closed cicuit system? The picture below is of a standard 1275 Cooper S with the PCV:

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I don't know why you are so against the closed circuit system? It works extremely well on our 1380, which are not exactly noted for 100% piston ring sealing, and definitely need all the breathing they can get. This week I had the opportunity to look at a Marina 1275 engined Minor, with the HIF44 carb connected to the timing cover - again very clean underneath.

The 1275 Minis (ok - not The S at first) all had a big breather on the transfer case.. That was after they realised the clutch didn't work too well when plastered in oil forced past the primary gear seal....... I'm not at all against the sealed system - but not many have the PCV valve - and it won't work without that.

Roy,

Can you look at this site please? It seems to say that all Minis (848 - 1275, including most 'S') from 1964 to 1969 were supposed to be fitted with a PCV and closed system (but there is a note to say that most single carburetted cars retained the open system!). Then, from 1969 to end of the production, all cars were fitted with a closed circuit system using either the carburettor port (HS or HIF) or single/multi-port fuel injection.

http://www.somerford-mini.co.uk/pdfs/Ca ... 9%20On.pdf

The earlier engines used the tappet chest or timing cover, and the later systems vented from either/both the timing cover and/or transfer case. There is more information in their main catalogue available for on-line viewing.

From what I read on the link is seems all the breathing is added to the outside of the engine.With all engines same being the same inside. Is this right?

If you are referring to the in-line engines, then in general terms yes. The Midget 1275 block is taller and slightly shorter than the 948/1098, but this has no effect on the ventilation system.

The 1275 blocks are both taller and longer then small bore blocks......which is why the 1275 oilpump has a longer drive shaft..... The somerford site is notoriously unreliable...... But yes - the engines were connected to the carb for fume removal - but with other open breathers to let air be drawn in and to let excessive fume escape without causing oil leaks when the engine is under high duress.........

So the 1275 transverse engine have a different ventilation system from the in-line? The 1275 Midgets all had the normal closed circuit system with the connection from the timing cover oil separator to either the PCV or to the later carburettor port, and the vented filler cap. US versions of course had a much more complicated set-up, but that is a different thing altogether.

Which production models of Mini had the system you describe, and where can I find details?

All later 1275 Mimi engines have an open breather on the transfer casing - and a suction tube from carb to a 'can' on the timing cover.