Twin HS4 Airbox

[111Robin]

I've been running with K&N cone filters on my twin HS4s for years but always wanted a more standard setup. Inspired by previous posts on modifying the HS2 box I've had a go myself. I decided to move the box back using spacers to clear the dash pots rather than cut away the front. More work obviously but looks ok. 12mm spacers give enough clearance but the box fouls the bulkhead so has to be reduced in overall depth. Cutting it back to the diameter of the filters works fine with just a small amount of modification to the inlet pipe as a result. I'll paint it once I've tidied up the welds but otherwise it's looking fine.

20200116_205804 by Robin Derrick, on Flickr

20200116_205748 by Robin Derrick, on Flickr

[bwaminispeed]

Looks good.....

[mk1]

Very good solution.

[AndyB72]

Looks very neat.

[Spider]

Very nice - it looks factory !

[CooperTune]

Could you post pictures of the other sides of the housing? I have a box with most of the tube cut off and missing
the lid. Looking for a air cleaner solution for a pair of HIF 38s. Steve (CTR)

[111Robin]

All I did was to continue the existing radius around the filters where originally the radius increased to capture the inlet pipe. I'll plate the section shown over the inlet. It reduces the depth of the box by around 0.5".

20200121_190806 by Robin Derrick, on Flickr

20200121_190733 by Robin Derrick, on Flickr

20200121_190832 by Robin Derrick, on Flickr

[CooperTune]

One more question, I can see from the brake parts this is a later car. Is it one with the sub frame drilled
for motor mounts 1/2 inch further forward and using the longer dog bone? I'm about to install a 1275 GT
power unit with twin HIF 38s. I have sourced a late sub with the forward mounting and longer dog bone.
All going in a early 90s BOC. Thanks for the pics. Steve (CTR)

[111Robin]

One more question, I can see from the brake parts this is a later car. Is it one with the sub frame drilled
for motor mounts 1/2 inch further forward and using the longer dog bone? I'm about to install a 1275 GT
power unit with twin HIF 38s. I have sourced a late sub with the forward mounting and longer dog bone.
All going in a early 90s BOC. Thanks for the pics. Steve (CTR)

It's an 89 model year but not sure about the engine position. Whatever was standard for that year is what it is, I'm sure someone on here will know.

[IAIN]

A 1989 mini 30, 1000 has the early mounting points on the subframe.

[111Robin]

A 1989 mini 30, 1000 has the early mounting points on the subframe.

Thanks Iain

[Vegard]

I've got a twin hs2 air box made from fiberglass. Maybe that would be easier to modify for such use. I cannot remember where I got it though.

[111Robin]

I've got a twin hs2 air box made from fiberglass. Maybe that would be easier to modify for such use. I cannot remember where I got it though.

Certainly cheaper than cutting up an original box but hey, it's only a glorified biscuit tin after all.

[Vegard]

[wulfy66]

How did you make the black spacer between the elbows and the inlet manifold? I have the same problem

[111Robin]

The spacers fit between elbow and carb, not the inlet manifold. I just bought a sheet of plastic of the required thickness (12mm) and cut it to shape.

[mk1]

This was the design I dreamed up years ago.

yry_13-s.jpg