Morris Minor Owners Club

Someone older and wiser than me told me that the air being drawn into the carb should be as cold as possible.

Why is it then that the most natural possition for the air filter housing has the intake 'pipe' right next to the exhaust manifold?

That's the winter position you turn it to the front near carb float chamber for summer.

If you have a late engine with oil separator chimney, it is a bit limited in how far forward you can rotate the air filter inlet or it will foul the chimney. You can still move it away from the hot exhaust manifold though. Yes I know there are two screws missing from the float bowl and the vacuum advance is disconnected. This is a photo from another job.

Many people put their classics to bed in the winter. If that is the case there is no need to change from the summer position. The theory is that cold air is denser than hot air and so per unit volume of air there are more molecules of oxygen in cold air than in hot air. That means more power in theory. In winter, having the intake nearer the exhaust manifold is supposed to stop carburettor icing.

Stephen

Thanks both.
What are the consequences of having the intake in the wrong place? Carb icing in winter?

Mine is in storage in winter so can't answer the icing carb question. I just leave it in the summer position and bought a better fitting breather hose, I don't have the chimney type it's straight off the rocker cover.

stuffedpike20 wrote: ↑Thu Aug 14, 2025 2:23 pm Thanks both.
What are the consequences of having the intake in the wrong place? Carb icing in winter?

I think the theory is if you have the air intake in summer position in winter you could get carb icing yes. I have many times forgotten to put back to winter position and I have never noticed any difference. I don't give my Morris a winter snooze but these days I am unlikely to take it out when there is salt on the roads which means it doesn't get used in below freezing conditions. There was a modification of the carburettor for very cold winter export countries. It was a type of electric carburettor heating system.

Stephen

Thanks folks.

I do alter the position of my carb intake for winter and summer (saucepan type) but how much difference it really makes, I don't know. I've never had any carb icing issues - but, then again, it doesn't get that cold down where I live.....nor have I suffered fuel vapourisation in summer, come to that.

svenedin wrote: ↑Thu Aug 14, 2025 4:30 pm

stuffedpike20 wrote: ↑Thu Aug 14, 2025 2:23 pm Thanks both.
What are the consequences of having the intake in the wrong place? Carb icing in winter?

I think the theory is if you have the air intake in summer position in winter you could get carb icing yes. I have many times forgotten to put back to winter position and I have never noticed any difference. I don't give my Morris a winter snooze but these days I am unlikely to take it out when there is salt on the roads which means it doesn't get used in below freezing conditions. There was a modification of the carburettor for very cold winter export countries. It was a type of electric carburettor heating system.

Stephen

Both of my US sold 948's have these heaters on the carb. I had a Datsun 510 1600cc that would ice over in the winter

Dear Stuffedpike,
Please note that carb icing is more likely above freezing, mostly in the 0-10C range (but can be much higher) and is very dependant on high humidity, say foggy conditions.
Read https://www.caa.co.uk/media/j5omfigm/ss ... -icing.pdf and scroll down to the chart.
Regards from MikeN.

Thanks Mike.
I did have an iced carb once....got to a T junction and the engine revs did not go down. It soon cleared though.

On my engine there is a breather pipe between the air filter and rocker cover. I do change the filter intake summer/winter, but need another, longer, length of hose for the summer position.
I didn't change from winter to summer for many years and found no detectable difference in running.

Mervin wrote: ↑Fri Aug 15, 2025 10:32 am On my engine there is a breather pipe between the air filter and rocker cover. I do change the filter intake summer/winter, but need another, longer, length of hose for the summer position.
I didn't change from winter to summer for many years and found no detectable difference in running.

Yes, and I'll wager that 'back in the day', the majority of Minor drivers didn't even think of moving the filter intake around.

"Yes, and I'll wager that 'back in the day', the majority of Minor drivers didn't even think of moving the filter intake around."
You're probably 100% correct. I must admit to not knowing it was an option until I discovered the revelation somewhere.
It's such a simple and logical thing to do too.
I wonder where I found the "revelation". I remember now, in the Minor 1000 Driver's Handbook.