Breather issue ???

[NoviceM]

Strange one.
I had a problem with rough running when at high revs.
I removed carb and cleaned carb etc.
Replaced carb, connected (nearly) everything back up.
Started ok. Checked Timing, running too advanced so retarded it. Checked with strobe vacuum advance and bob weights seem to be working fine.
Checking plugs, seemed a bit "lean" so richness off 8 flats.
Runs great, hesitation at high revs has been fixed.
BUT... I then noticed the pipe from the valve chest canister was disconnected from the tube on the carb.
If I try to reconnect, the car dies almost immediately. It will NOT run with the carb tube blanked off (by pipe or finger)
I am reluctant to experiment too much, since the car runs very well.
I have connected the "carb" end of the tube to the tube on the air filter body, rather then let it dangle about.
Any one any idea what might be going on, and what, if anything, should I do.
Any suggestions greatly appreciated.

[svenedin]

You have adjusted the fuel mixture so that the engine is now running well with the carburettor breather tube drawing in air. When you block the tube with your finger or by connecting to the tappet chest oil separator you are blocking off the air being drawn in and the mixture is then becoming so rich the engine will not run. You need to reconnect the breather pipe to the carburettor and make the mixture leaner.

Stephen

[philthehill]

What number/letters are quoted on the carb tag attached to the float chamber?
Once we have the answer to the above question no doubt an answer will be forthcoming.
I suspect that you do not have the correct carb and/or main jet needle.

[myoldjalopy]

A bit more background might help. You say "I had a problem with rough running when at high revs." Did this just occur out of the blue, or had you done anything to the car beforehand?

[geoberni]

I agree with Stephen, you set everything up and then went and changed the air supply configuration.
It's no wonder it's playing up.
Repeat the setting it up with the pipe connected.....

[svenedin]

You said the plugs looked like the mixture was too lean so if I am understanding correctly you adjusted towards rich by 8 flats (this is a lot) BUT there was nothing connected to the carburettor breather intake tube at this time. Now you have an engine with a mixture adjusted towards rich to tolerate air going in through the carburettor breather inlet. When you block off that inlet with your finger no fresh air is going in so the mixture is becoming so rich the engine stalls. You need to reconnect the breather pipe and adjust towards lean. It may be the mixture is so rich the engine will not start at all so try adjusting towards lean half of what you originally adjusted towards rich e.g 4 flats towards lean. Remember that the mixture is even richer with the breather system connected than it is by blocking the carburettor breather inlet with your finger because oil fumes are going into the engine too. You will almost certainly have to go further towards lean to get satisfactory running but count the flats so that it doesn't end with a complete muddle.......

For those not familiar with this type of breather system this is an oil separator canister that looks like a chimney on the forward tappet chest cover with a rubber tube going from that canister to an inlet on a special type of HS2 carburettor that has a breather inlet. This system was used in very late Minors at there very end of production and superseded the previous (short lived on Minors) system of using a PCV valve.

Stephen

[NoviceM]

Many thanks for the helpful replies.i will readjust by leaning off and reconnecting breather tube as suggested.

[svenedin]

Please let us know how you get on

Stephen