15 replies to this topic

[newenglandmini]

What is this item on my Canadian 1974 998 cc engine?  It appears to be attached to the rear of the engine, below the exhaust manifold.  I think it was plumbed to the intake manifold with a rubber hose.  I presume it is an emission control component.

 

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[wilz1234]

Looks like the tappet chest breather

Edited by wilz1234, 10 January 2014 - 08:50 PM.

[Craig89]

It's a breather for the pushrods/followers. It releases the pressure and is plumbed into the inlet so the fumes can be burnt off

[newenglandmini]

Thanks.  In the US it's referred to as a PCV valve (positive crankcase ventilation valve).

 

Here's another item I removed.  Is this a fuel vapor device?  We had devices on US cars in the '70's that looked similar.  They were referred to as "charcoal canisters" because they contained activated charcoal which would absorb and retain fuel fumes from the fuel tank and carburetor.

 

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[dklawson]

Corey, that breather on the back of the block is not the same as our PCV valves.  There is no valve inside, only coarse steel wool like you use to clean a gas grill.  Fumes from the crankcase pass through it and the intention is that the heavier, coarser oil drops collect and flow back into the engine.  The fine oil mist continues one out of the breather through that hose connection on the top and go to a Smiths PCV valve that mounts next to the carb(s).  The Smiths PCV valves are sort of funnel shaped aluminum castings with a rubber diaphragm, valve plunger and spring inside.  The picture below shows the PCV valve and breather on a Morris Minor. The early Mini was similar.  The thing next to the oil filler cap is the PCV. 

 

I don't know if Canadian spec Minis had the carbon canisters or not.  They certainly were on the Mid-70s MGs and Triumphs.

 

[newenglandmini]

Doug, thanks for the clarification.  I plan to modify the oil breather system to the old style road draft configuration.  That will comprise piping from the crankcase to a location at the bottom of the engine bay to draft the crankcase blowby fumes.

 

Likewise, the charcoal canister system can be dispensed with to simply allow the fuel tank to vent to atmosphere.

[dklawson]

The simple draft tube will work but it can be messy.  You may want to retain the tappet cover breather and plumb it into your draft tube to minimize the amount of oil dripping behind you and on your garage floor.

[newenglandmini]

Here's another one.  This appears to be an electric carburetor air pre-heater.  I assume it's an emission control device, though since my car is Canadian it may be be intended to improve cold weather performance.  Can someone clarify please?

 

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[newenglandmini]

And yet another.  This one appears to be a throttle damper.  Is this also emissions related?

 

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[newenglandmini]

One more.  This one was wrapped around the caburetor damper housing and had a black ground wire attached the the knurled knob terminal.  Odd!

 

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[dklawson]

Those are carb and intake charge heater parts common on 1275 engines used with the Austin America (AA).  I don't know how they are controlled.  The AA must have had some form of thermostat to turn them on and off.  Being in Connecticut, you may want to use them for winter driving.  Take a look at my friend Todd's site for the Austin America.  He may have information on how to wire them up.

http://www.austinamericausa.com/

[Vipernoir]

Having suffered from bad carb icing on a few cars, i'd hang on to the SU warming devices as your climate is much colder than ours.

 

They were fitted to Canadian spec cars for a reason...

[Dan]

I think the thermostat for the heating devices is in the black bulb fixed to the heater/spacer. They used to call them something really odd like Otter switches.

[newenglandmini]

And yet another.  This one appears to be a throttle damper.  Is this also emissions related?

 

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Any thoughts on what the damper/spring bit is?

[Dan]

Yes as you suspected it's a throttle damper. These cars had three separate but related emission control systems, as more modern cars do too but now it's all controlled digitally so it's more straightforward. There is the evaporative loss system (charcoal canister and hoses) that traps and burns fuel vapour from the tank, float bowl and lines. There is the exhaust emission control system that injects air into the exhaust ports to ensures clean burn (more basic and less efficient than a cat but allows more tolerance for the fuel ratio, some cars now have air injection and cats together), and also injects air into the inlet under over-run for the same reason. Then there is the crankcase emissions system as used by later models more or less unchanged. The throttle damper is part of the air injection system and stops the throttle snapping closed too quickly, I believe because the gulp valve that added air to the inlet wouldn't respond as quickly as the throttle would snap closed naturally. This would play havoc with the mixture as you came off the throttle and the car would surge. The damper allows the throttle to close at a rate the gulp valve can match. If you have ripped out the air injection system then the damper isn't needed.

I would personally keep the PCV system in place but you don't need the manifold valve for it. Use a carb with a proper emissions connection and just hose the various breathers to that. If you have just an old carb without an emission port then maybe you are best going back to open breathing because the valves are unreliable when old. Although they can be effectively overhauled it will always be a pain at service. If you do go back to open breathing just don't kid yourself that 'road draught' actually works as advertised and simply accept is as an open vent.

The carb heaters are as you say for cold weather running and well worth keeping. Hopefully you still have an arctic spec heater fitted, as was original.