Morris Minor Owners Club

I know this is going to get me into trouble but ive added a BB Classics SS Pancake Air filter (& stub stack) for a bit of under-bonnet bling. But it feels like the engine is strangled a bit. Is the original filter the best solution?

Fitting the pancake air filter may and most likely will effect the mixture so you need to check that.
When fitting the stub stack and the pancake air filter is not deep enough the flow of air into the carb will be restricted so strangling the engine.
Bling is alright but it has to be done with some thought as to how it is going to work and what the outcome will be.
The air flow through the factory air filter set up is good - so yes it is better to stick with the original air filter system.
A couple of photos of the pancake filter and the fitment of the stub stack would be appreciated.

philthehill wrote: ↑Mon Jun 09, 2025 11:13 am Fitting the pancake air filter may and most likely will effect the mixture so you need to check that.
When fitting the stub stack and the pancake air filter is not deep enough the flow of air into the carb will be restricted so strangling the engine.
Bling is alright but it has to be done with some thought as to how it is going to work and what the outcome will be.
The air flow through the factory air filter set up is good - so yes it is better to stick with the original air filter system.
A couple of photos of the pancake filter and the fitment of the stub stack would be appreciated.

Thanks

I'll do photos tonight. i did wonder if filter too shallow

Pics

I like the bling and that filter does look very smart but I suspect the foam element is rather more restrictive of air than the paper element in the Series V air filter. Due to that air restriction the fuel/air mixture is probably too rich (not enough air to the quantity of fuel). You could try leaning the fuel mixture taking note of how many flats you have adjusted by so that you can put it back to how it was with a standard air filter if it comes to that. I'd suggest taking out a spark plug and examining it to get an idea of the fuel mixture. The other thing you could do is run the engine (for a short time) without the foam in place. Does it run normally then?

Stephen

That foam does look rather dense in a quite thin housing...
Add the depth of the outlet into the Carburettor and I would think that overall it's really choking the air supply.

I would suggest that you ditch the bling and go back to as per factory air filter installation
That stub stack is too deep and is restricting the flow of air into the carb.
You could remove the stub stack and re-fit the air cleaner and see if it makes any difference.

All good point. I'll try without foam & then original and see.

I had a feeling it was a bit cheap & cheerful!

Ran engine without foam, ran awful needed to richen the mix just to get it to run half decent.

Used to think the KISS principle was Keep It Simple, Stupid. But now realise its Keep It Standard, Stupid

Thanks all

I did suggest that you run the engine without the stub stack. Taking out the foam will have no effect if the outer face of the stub stack is too close to the lid of the pancake filter body.
Normally a plain pancake air filter without the stub stack fitted will not cause problems though you may have to adjust the mixture slightly.
The stub stack can only be fitted if there is adequate clearance between the entry of the stub stack and the air filter body.

philthehill wrote: ↑Wed Jun 11, 2025 2:33 pm I did suggest that you run the engine without the stub stack. Taking out the foam will have no effect if the outer face of the stub stack is too close to the lid of the pancake filter body.
Normally a plain pancake air filter without the stub stack fitted will not cause problems though you may have to adjust the mixture slightly.
The stub stack can only be fitted if there is adequate clearance between the entry of the stub stack and the air filter body.

Sorry didnt mention i ran pancake as bought and noticed issue straight away so bought the stub stack thinking it may help but it didnt. So now run filter as bought, filter without foam, with foam + stub stack, stub stack on its own with no filter housing & foam (this was worst!). So as you said in last post ditch the bling and return as the engineering team intended

BTW is it normal for modern OE paper filter elements (from ESM) to be ever so slightly too tall (1-2mm) and the canister not being able to close completely?

Wes wrote: ↑Wed Jun 11, 2025 4:21 pm

philthehill wrote: ↑Wed Jun 11, 2025 2:33 pm I did suggest that you run the engine without the stub stack. Taking out the foam will have no effect if the outer face of the stub stack is too close to the lid of the pancake filter body.
Normally a plain pancake air filter without the stub stack fitted will not cause problems though you may have to adjust the mixture slightly.
The stub stack can only be fitted if there is adequate clearance between the entry of the stub stack and the air filter body.

Sorry didnt mention i ran pancake as bought and noticed issue straight away so bought the stub stack thinking it may help but it didnt. So now run filter as bought, filter without foam, with foam + stub stack, stub stack on its own with no filter housing & foam (this was worst!). So as you said in last post ditch the bling and return as the engineering team intended

BTW is it normal for modern OE paper filter elements (from ESM) to be ever so slightly too tall (1-2mm) and the canister not being able to close completely?

No that's not normal. Sometimes the paper element is not centred properly and then the cover will not close. The silicone base material of the element makes it tend to stick to the base plate so it does not self-centre. Try again, taking care to place the element centrally on the base plate and then fit the cover. Sometimes you wish you had 3 hands.......other times it just goes on no fuss whatsoever. Or I suppose you could fit the element in the cover, hold it with your fingers and then offer up the cover to the baseplate. Never tried that though.

Stephen

We bought a 62 Moggy that had been restored a few years ago now, It came with a Chrome Pancake Air filter. Not found a problem with it, have driven the car several miles now and all seems ok.

Allen70
How deep is your chrome pancake air filter and does it have the stub stack fitted?

[/quote]

No that's not normal. Sometimes the paper element is not centred properly and then the cover will not close. The silicone base material of the element makes it tend to stick to the base plate so it does not self-centre. Try again, taking care to place the element centrally on the base plate and then fit the cover. Sometimes you wish you had 3 hands.......other times it just goes on no fuss whatsoever. Or I suppose you could fit the element in the cover, hold it with your fingers and then offer up the cover to the baseplate. Never tried that though.

Stephen
[/quote]


Thanks for this. maybe the canister is bent. Might buy anther element to see if one i have is off-spec Chinese knock off ;-)

Reply to Phil, Hi no stack and the Chrome metal pancake is about 1 inch to inch and a half wide with foam filter, we have had the car now around 3 years.I'm not saying it's correct, but it does run well and starts first pull. Thinking about it, I suppose it would not hurt it to replace the foam filter with a similar foam or try and think of something better than foam. Any Ideas ?

I think the idea of the foam is that you can clean it with water and reuse it like the filters in some vacuum cleaners and tumble dryers. First thing I would do is wash and dry the filter.

The rather expensive K&N pancake air filters do have replaceable paper elements which I assume are much less restrictive than foam.

Personally, I'm sure the standard air filter is fine with the standard carburettor but it may start to restrict a bigger inlet carburettor.

Stephen