The idea here came while I was browsing eBay one day, all these modern cars have bespoke cold air induction systems, so why not the Marina?
Stage One - the Mk1 Marinas had the 'Tapir' snout type air cleaner and filter mounted off the carb(s). My SDL filter snout pointed in the general direction of the front panel, where there are two smallish holes to let in cold air. The TCs snout points over the rocker box to draw cooler air from the other side of the engine. I think this really is a 1960's hangover; as the Mk2s & 3s had a cold air feed from the left side of the front panel. That was then blended with warm air off the exhaust manifold, before hitting the filter, which was still mounted off the carb(s).
(my SDL single carb - before K&N)
(TC feeding off cooler air)
Stage Two - those Marina-ists that have fitted a K&N filter like me, will know that the K&N does two things; breathes more easily (like the Tunes sweeties) and ruins the mixture settings. I have just fitted a revised needle which seems to have cured this and released a bit more power and tractability into the bargain. The original needle was a BAS and the new needle is a BBW.
There are also two hidden consequences of this mod; the K&N recommended filter for the single carb SDL is large, the bottom edge can clash on the inner wing if the engine rocks a lot and the engine is drawing exhaust manifold heated warm air rather than the lovely cold stuff.
The TC has options of using the MGB filters which are smaller in diameter and offset to avoid hitting the inner wing. Unfortunately they only seem to come in 11/2" size, not 13/4", otherwise you could fit them on the single carb. This would however be an option for the single carb 1.3 litre Marina.
The first can be overcome by ordering a 13/4" filter for I believe the MGC and Morris 1800 (K&N pat no 56-9096), it has a smaller diameter and seems to clear OK. I got mine from Moss-Europe, but any Halfords can order it for you.
The second problem can be helped by Pipercross Ltd., one end is mounted in the front panel behind the grille and the other is positioned close to the K&N filter and mounted on the inner wing with a simple bracket/cable tie/etc. These hoses are available from Halfords at around £25.00.
You will have to open up the hole in the panel to get a good fit, or use the existing mounting if you have a Mk 2 or 3.
Of course the cheaper way is to pop down the scrap yard and find some hose off another car. If you want something new and shiny, Halfords stock aluminium hose up to 60mm in diameter.
Stage Three - is to get the filter off the engine completely and mount it remotely (like behind the front panel), this overcomes the problem of the filter hitting the inner wing. Then all you need is an air hose connecting the remote filter to the carb.
When I took the original filter off my SDL, like a fool I threw away the filter neck elbow and filter housing. The filter neck elbow would have been ideal to fix a hose to, likewise for a 1.3. My SDL neck was angled upwards at about 45 degrees and rolled forward through 90 degrees. If you look at other SU carbed BMC/BL cars, the necks vary in angle and length.
Help is at hand from the BL range as most Rover V8s used 13/4" carbs, nice and short and angled to offset the carb angle. These pics were both on eBay, I have bought the HIF44 carb to experiment with.
Another option would be from an Austin/Morris 1800, I saw some at a recent Autojumble, including the HS6 carb they were only £10 each.
Having sorted out the carb end, Pipercross or Green Filters can supply the enclosed filter for the other end.
Pipercross Viper - I would mount the narrow filter end into the Marina front panel and move the hose to the other end of the unit and link it to the carb filter neck.
Personally I prefer Green Filters Twister as they have nice shiny silver, blue or red canisters to match in with the engine bay colour scheme, rather than the carbon fibre look of the Pipercross.
Green Filters can supply 'Top Hat' adaptors to make things easier. .
Green Filters can also supply inlet vents with a mesh filter to stop leaves etc getting into the system and reducing airflow
As you can see the Green Filters range allows you to build up a bespoke system to suit your needs. You can buy online or from one of their distributors.
Stage Four - once the filter is off the engine and secure on the wing panel, the next step will be to mount the twin SUs that I have yet to renovate. Once again I will need a richer needle as the air system will be less restrictive than the original, thanks to the MGB boys Burlen Fuels list rich needle options for each of their MGB twincarb refurb kits.
(another eBay purchase)
The virtue here is that I only then need a plenum chamber to fit the carbs, as the filter is mounted elsewhere. I have some ideas for this but as the carbs aren't ready, I'll wait until I can fit them and then sort something out, watch this space.