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Twin HS4 Airbox

Posted: Sat Jan 18, 2020 9:23 pm
by 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.

Image20200116_205804 by Robin Derrick, on Flickr

Image20200116_205748 by Robin Derrick, on Flickr

Re: Twin HS4 Airbox

Posted: Sat Jan 18, 2020 9:34 pm
by bwaminispeed
Looks good.....

Re: Twin HS4 Airbox

Posted: Mon Jan 20, 2020 1:45 pm
by mk1
Very good solution.

Re: Twin HS4 Airbox

Posted: Mon Jan 20, 2020 1:57 pm
by AndyB72
Looks very neat.

Re: Twin HS4 Airbox

Posted: Mon Jan 20, 2020 4:30 pm
by Spider
Very nice - it looks factory !

Re: Twin HS4 Airbox

Posted: Tue Jan 21, 2020 2:18 pm
by 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)

Re: Twin HS4 Airbox

Posted: Tue Jan 21, 2020 9:59 pm
by 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".

Image20200121_190806 by Robin Derrick, on Flickr

Image20200121_190733 by Robin Derrick, on Flickr

Image20200121_190832 by Robin Derrick, on Flickr

Re: Twin HS4 Airbox

Posted: Wed Jan 22, 2020 2:07 pm
by 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)

Re: Twin HS4 Airbox

Posted: Wed Jan 22, 2020 6:30 pm
by 111Robin
CooperTune wrote: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.

Re: Twin HS4 Airbox

Posted: Wed Jan 22, 2020 10:56 pm
by IAIN
A 1989 mini 30, 1000 has the early mounting points on the subframe.

Re: Twin HS4 Airbox

Posted: Thu Jan 23, 2020 7:00 am
by 111Robin
IAIN wrote:A 1989 mini 30, 1000 has the early mounting points on the subframe.
Thanks Iain

Re: Twin HS4 Airbox

Posted: Mon Feb 10, 2020 11:44 pm
by 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.

Re: Twin HS4 Airbox

Posted: Tue Feb 11, 2020 7:17 pm
by 111Robin
Vegard wrote: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.

Re: Twin HS4 Airbox

Posted: Tue Feb 11, 2020 11:37 pm
by Vegard
:lol:

Re: Twin HS4 Airbox

Posted: Tue Aug 20, 2024 8:32 pm
by wulfy66
How did you make the black spacer between the elbows and the inlet manifold? I have the same problem

Re: Twin HS4 Airbox

Posted: Tue Aug 20, 2024 8:44 pm
by 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.

Re: Twin HS4 Airbox

Posted: Wed Aug 21, 2024 8:11 am
by mk1
This was the design I dreamed up years ago.
yry_13-s.jpg