Carburettor air intakes

[ankaili52]

Hi, I have a 1961 3.8 Mk 2, with twin 2" carbs. They are fitted with air-trumpets, and so to protect the engine from grit and other contamination I use a kind of circular foam 'sock' to cover them.
However, I have recently noticed several cars (including Vicarage restorations) fitted instead with 'short ram pipes' that have a kind of spherical grating to presumably act as a filter. These are being sold by Burlen who are the SU supplier.
Does anyone know of these, and how they compare to the traditional air trumpets in performance?
Thanks!
PS I tried to upload an image but it didn't want to.

[PPV]

Has your car been modified to have 2" carbs? Ram pipes tend to only have a mesh unless a 'sock' is fitted so there is little filtration. If you are after some benefit then I would look at K&N filter units which tend to offer better breathing.
Regards,

[ankaili52]

Hi PPV,

My car had 2" carbs from new, it was built by Jaguar for a racing driver, and has several other non-standard features.
When I bought it nearly 10 years ago, the previous owner had used circular wads of felt to give some sort of filtration, but my research discovered that in racing the air trumpets would not usually be covered at all. I found out that CMC were fitting foam 'socks' to cars they restored with open air intakes to filter out grit, etc. in daily driving, so bought a pair myself.
I was just wondering if the perforated chrome "shower heads" I have now started to see on some cars would be any better.
Thanks for your interest.

[piman]

Hello Ankaili,

I have had a look on the Burlen website and all I can see are trumpets fitted with a mesh domed cover, these do not provide any effective air filtration.
There is not a lot of room in a MK 2 between the wings and the carburettors. However it may be possible to use the same system that Aston Martin used on it's DB4,5 and 6 cars, This was a rectangular air duct bolted to the carburettors but with trumpets fitted inside the air duct. This was then connected to a remote air cleaner using a flexible duct hose.
They also show K and N pancake type filters which is another option?
Alec

[Ronniebiggs]

Piman etc,

Trumpets, if of suitable radius at the flare, do aid breathing. Mesh covers, of any flavour, ruin breathing and don't filter! The amount of debris ingested by an engine without filters is quite terrifying, and forms an excellent grinding paste when mixed with fluids in an engine. In the 'old days' of Cosworth DFVs in F1 an unfiltered engine would lose around 50hp after one race due to wear caused by such muck.

The large circular paper cleaners, as fitted to 3.4 Mk2s etc, breathe well and are excellent filters. They also silence the intake effectively.

Due to limited space there's not a lot on the market that will do as good a job as the standard fitment, so you'll probably need to use stub stacks (short, radiused thingies like miniature trumpets) inside a plenum fed by a remote filter.

Jay

[340jag]

I have HS8's and have fitted Pancake Air filters !

[Ronniebiggs]

If you look at the intake area for the two pancakes, it's a lot less than one standard air cleaner! That means much (most?) of the gain of the 2" carbs is almost certainly lost, and you have lower gas speed to boot.

Yer pays yer money...

[340jag]

The surface area of the pancake for each carb is bigger then 2 inches , a filter could be as big as a dustbin, but the Air has to go into a 2 inch intake , more Air is going in to the carbs then a standard paper air cleaner