Filter options for Twin H4 SU

[Rubbersoul]

What are the filter options for Twin H4 SU on a road going car. I would prefer to avoid K&N type filters.
Would it be possible to fit a Mk1 airbox from a pair of 1 1/14 SU for example?
Thanks

[Peter Laidler]

GOOD question Rubbersoul.

Unipart spent a long time - and money - sponsoring the automotive engineering minded engineering universities. One of their projects that I was aware of and to cut to the quick, because there is more to it than first seems, is the performance of air cleaners for road use across all climates.

By far away ahead, were COOPERS. Unipart contracted with Coopers and all UNIPART branded air filters after the mid 70's were......, guess what? Yep, Coopers. As part of the contract and to keep the prices down, that's why the COOPERTS label ( and later, UNIPART) was attached to the filter box*. The TROUBLE with them is that they don't look Gucci or expensive

* don't hold me to that. Learned second hand from Unipart later

[Rubbersoul]

I can't say i am interested in a matter of 1hp gain because of a pair of K&N. Normal air cleaners would do but I need a housing that fits them in
Trouble is I cant see many options for H4. What did the works do? leave the filters off altoghyether?

[111Robin]

The airbox for twin 1-1/4" can be modified to suit 1-1/2"s. The box & lid need to be cut down to just fit the filters as it is too wide otherwise and fouls on the bulkhead. I made nylon spacers between the carbs and elbows to push the box back so that it cleared the dashpots. Elbows are standard 1-1/4" with the bores opened out. If you can find a rotten old airbox have a go, unforunately these are expensive items these days so cutting one up is drastic but ends up looking factory.

[Rubbersoul]

Thanks for that. The whole engine bay looks really good. Unfortunately my carbs are the older twin H4 SU as used on 'works' cars (not HS4 that your car appears to be fitted with)
Has anybody carried out a similar adaptation for their H4 set up?

[Oneball]

Baseplates come blank or MED sell them as a kit for twin 1 1/2”

8825B49A-EB2D-415C-9522-B9CB05DC4667.jpeg

[Peter Laidler]

Simplicity itself. But typically, two flat alloy plates approx the size of the original air cleaner box shown above, with holes in the LOWER plate to suit the dia of the carb openings and spacing apart. Also two - or 4 with twin carbs - holes to allow plate to be bolted through, to the carbs

Top plate, identical to the bottom plate but LESS the carb openings. 2 (or 4) bolt holes identical to bottom plate.

Sandwich air filters between top and bottom plates. Gasket between carb and bottom plate. Bolt through and screw down.

If you want them angled with the back of the carbs or horizontal as per HS's, you decide. But the principle is the same

Now you have what MGB GT G8 owners have been doing for years. 360 degrees - or 640 mils - of all round air intake into the carbs via the new fangled 'box' and filters.

You can titivate the sandwich plates to whatever takes your fancy. But we REALLY don't know what you have......

[Herbert]

Currently I run H4's and have 2" ram pipes. For filters I use socks filters, all seems fine.
I took the car to John Lee's rolling road when Peter Baldwin was there. First I tried running HS2's and when I put on the Unipart filter I lost 12 hp !!!
When I fitted the H4's with or without the sock filters it made no difference, so they work. I wash them and then soak them in thin oil. I now get 117hp at the flywheel, so Im happy !

[richardACS]

What are the filter options for Twin H4 SU on a road going car. I would prefer to avoid K&N type filters.
Would it be possible to fit a Mk1 airbox from a pair of 1 1/14 SU for example?
Thanks

I'm in the process of doing the same - Downton used to fit the Cooper Filter and these are still available through Holden Vintage and Classic but you have to search through for SU 1 1/2 for Austin Healey 015.416 they come with or without the hose tails approx £32.50 plus delivery and vat. I have them ready to fit but as yet don't know for sure they will have the necessary all round clearance in the engine bay but Downton seemed to do ot ok. As mentioned by others there does seem to be a drop in horse power....

[Fanfaniracing]

What about a Vortz Airbox?

4D034660-E14A-487B-9C9A-E0FA1D2D1ADF.jpeg

[timmy201]

I believe H4 and HS4 have the same air filter flange.

I’m still deciding what to use for my H4 carbs, I’ve got some Les Leston ram pipes which would need some socks, and also some Ramflo chrome filter units

Example from Burlen:
https://sucarb.co.uk/air-filters-ram-pi ... -hif4.html

Ramflo. There’s normally enough room for a stub stack
https://minisport.com.au/mini-moke-ram- ... y-1-1a2-su

[Andrew1967]

I am planning to fit a set of Speedwell H4’s that I obtained with a 1071 engine/box to 9748KO and was going to fit socks to the ram pipes.

[MiNiKiN]

What about a Vortz Airbox?

4D034660-E14A-487B-9C9A-E0FA1D2D1ADF.jpeg

What brand of "Keksdose"* did Vortz use as a basis?

*cookie tin box

[rolesyboy]

I’m surprised nobody has started making these Vortz airboxes.
Twin h4’s are so popular

[Exminiman]

I’m surprised nobody has started making these Vortz airboxes.
Twin h4’s are so popular

Or any SU airbox in fact, can find the lids but no boxs ?

They are actually not far from a biscuit tins…..

Something like this could work, with a few mods, might be cheaper than buying one of ebay

D0A23F76-B284-4561-8CFA-A45F83A581A3.jpeg

[surfblue63]

I've often wondered if it was possible to adapt a filter box from a MkIV Spitfire/MG Midget 1500?

[mk1]

I have done the airbox conversion in the past & it does work very well. However, I very much doubt that it would fit with H4's as the body is a little longer & everything is pushed back a bit.

The original Cooper aircleaners used by Downton are aesthetically very pleasing, but if you are looking for ultimate power not an option.

All original air cleaners (including socks) look totally pants in my opinion.

So for H4's I either use open trumpets like on the Speedwell car or the original Downton style cooper wire wool Aircleaners. My option on my current car are the Cooper ones. It's for pottering about in and looking good, I'm not bothered about ultimate power, it'll be making close to 90 at the wheels, so if it loses 15 because of the antiquated filters, it is as far as I am concerned a price well worth paying.

Stu's suggestion above, looks like an interesting option.

M

[Polarsilver]

Fitting the Midget 1500 airbox would be an issue with my H4,s as this would foul onto the carb fuel in/out banjo fittings unless these car rotate inwards .. then this could become an issue with LCB exhaust heat as no heatshield is fitted.. also the 1500 airbox air intake would need to be away from the clutch master cyl; as that area clearance would become very close .. me thinks some major modification of that Midget type airbox would be needed.

[mk1]

I have bought one & am going to have an experiment.

[Oneball]

Inside the the Spitfire air box are two complete pancake filters with plates, unless you want to route cold air pipes to it you could just use two pancake filters. They’re big as well, I’m not sure it’ll clear the bulkhead.