15 replies to this topic

[Uncle Bobby B]

Hi all,

I have recently acquired a pair of HS2’s but will they work on my 998? The engine is completely standard apart from a stage one kit. I’m not looking for any performance increases as I know they won’t have much impact, it would simply be for the aesthetics.

[timmy850]

Twin HS2 were a popular period upgrade for 850 engines, so they’ll work fine on a standard 998. Perhaps you’ll get slightly better response than a single HS4, but overall performance will be similar

You’ll need to make sure the twins are in excellent condition, and matched to respond the same way during tuning

[cooperd70]

They sure will but as timmy850 says they will need to be matched to respond as one another during tuning. As well as a period upgrade they were also part of the John Cooper Conversion pack fitted by Cooper Garages in 1990 as an optional extra to the Flame Red, Racing Green and Checkmate 998 minis

[Steam]

Twins will give a more even mixture per cylinder as each carby splits evenly. You will need to get the correct needles and set up perfectly. to be honest its all too much hassle for me I would always fit a single over the twins I have here.

Edited by Steam, 14 April 2025 - 06:55 AM.

[Uncle Bobby B]

That’s great news, thank you timmy850 and cooperd70! Do you have any suggestions on how to ensure they are matched perfectly?

[Uncle Bobby B]

Steam - what makes it a hassle?

Plus, how do I ensure the needles match?

[Steam]

You have to balance them which is, to put it mildly, a PITA. Each has to be set independantly on the linkages which are prone to slipping.
You would need to make and educated guess at needles initially then get a rolling road tune by someone who knows twin SUs.

[timmy850]

It’s something along the lines of:
Learn how to tune a single SU
Check the air fuel ratio with a gauge and get the mixture correct right across the rpm and load range
Once you’ve sorted out single SU tuning the same principle applies to twins, with the exception that they much be evenly matched. Same drop and rise rate on the dampers, jets and needles setup evenly, linkages, idle stops, etc all set the same to give even fuelling


You can get them started and running with some suggested needles, but the last 50% of getting any SU carb running properly is in the fine tuning. This takes lots of time, effort and measuring , or send it to someone who knows what they’re doing

[68+86auto]

Since you are asking this question, I'd say stick to a single carb.

 

Plenty of people fit twin carbs for looks etc and then complain they are difficult to adjust/maintain. Without good knowledge of carbs, you'll join them in saying that.

Edited by 68+86auto, 14 April 2025 - 11:18 PM.

[timmy850]

If it costs you a few afternoons in the garage and a new manifold gasket, then I’m all for it if you want to try something new and learn. Minis don’t always have to make sense

You can always swap back to the single if you can’t get it to work

I’ve tried a few different setups over the years on my mini (over 2 different engines) and sometimes the best way to learn is just to give it a go. I’ve had an air fuel ratio gauge for tuning which is the only way to do it
Single HS2
Single HS4
Dellorto DHLA
Twin HS2
Single HIF44

[cooperd70]

I cheated...I had my twin HS2's setup by Colin at SMMC. They have been perfect since 🙂

[Cheeser]

It may help to read something like this?

https://www.calverst...fo/carburation/

[Uncle Bobby B]

Thank you for getting back to me everyone! I’m always up for learning and I’ve found with anything mini related it takes time 😂
I think my next purchase needs to be an air fuel ratio gauge!

[gazza82]

I once got asked to help set up twin SUs on a neighbour's MGB. He produced an expensive air flow tool .. after 20-30 mins of checking and adjusting we still couldn't get it to run correctly.

I pulled a piece of rubber hose out of my toolbox, placed it on the edge of the carb opening and then listened to the second. When the noise was the same after adjusting both the car ran perfectly.

I think I saw him throw the meter in his dustbin as he went home!

[nicklouse]

Hi all,

I have recently acquired a pair of HS2’s but will they work on my 998? The engine is completely standard apart from a stage one kit. I’m not looking for any performance increases as I know they won’t have much impact, it would simply be for the aesthetics.

They will give no performance increase, you may even experience a loss in performance as you will lose air speed in the induction side. You will also need a new exhaust manifold unless you cut up the original cast manifold if they will fit. Fitting the new exhaust manifold will really need a suitable exhaust system.

 

and after all that the carbs will need setting up to run correctly. All in all a lot of cash just for looks and more noise in the cabin.