Single to Twin SU Worth It?

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
Tornado99
Posts: 15
Joined: Thu Dec 24, 2020 9:03 pm

Re: Single to Twin SU Worth It?

Post by Tornado99 »

I'm in BC Canada and do not know of any rolling road facilities in the region. So not likely it will ever be possible to get that level of tuning done.
This twin idea came up bc I came across a complete twin SU setup for mini on a used parts lot for sale. With the input here and other forums, seems the wise option is to stick with what I have and avoid introducing more complexity than I can sort out.
mascher
Posts: 112
Joined: Thu Jun 24, 2010 5:12 pm
Location: Seattle Washington

Re: Single to Twin SU Worth It?

Post by mascher »

If you're still using the original intake and exhaust manifolds, I would say keep the HS4 and change to an alloy intake manifold and a Cooper free flow exhaust manifold. Cleaning up the HS4 throat should help a bit as well. This works well on an engine that you're not going to rev much above 5500 rpm.

Kelley
De-hira5729
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Joined: Fri Feb 17, 2023 3:59 pm

Re: Single to Twin SU Worth It?

Post by De-hira5729 »

I didn't feel like using HIF very often in Japan, so it's very fresh.
I would love to try it! !
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MiNiKiN
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Location: Graz/Austria // NN1 4ST previously

Re: Single to Twin SU Worth It?

Post by MiNiKiN »

Tornado99 wrote: Thu Mar 02, 2023 8:06 pm I'm in BC Canada and do not know of any rolling road facilities in the region. So not likely it will ever be possible to get that level of tuning done.
This twin idea came up bc I came across a complete twin SU setup for mini on a used parts lot for sale. With the input here and other forums, seems the wise option is to stick with what I have and avoid introducing more complexity than I can sort out.
Not having access to a rolling road is no excuse. Simply fit a broad-band O2-sensor (Lambda-sensor) to the LCB manifold connected to a black-box or A/F-Meter. Such you can set-up the carbs on the road - better than on many rolling roads.

I have a Zeitronix System that even records the AF-Signal along with other sensor signals (rpm, throttle pos, temperature, etc - many optional input signals ). You could define a certain test track and navigate it with defined throttle positions - so you see how the AF-ratio behaves over the revs and correct it en route with different needles to match. e.g. https://www.lambda-tuning.de/zeitronix_ ... sonde.html
Yes I am a nerd: I am researching the Austrian Mini-racing scene of the 60s and 70s :ugeek:
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Rolandino
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Location: Berkshire

Re: Single to Twin SU Worth It?

Post by Rolandino »

I'm not sure if anyone has told you this on this thread but if you go from single carb to twins, you have to not only change the inlet manifold but you need a new exhaust manifold and all the rest of the exhaust system. It will give you more power, better torque and higher revs which can't be used with benefit unless you change the gears to S ratios. Good luck! R
Alex
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Re: Single to Twin SU Worth It?

Post by Alex »

Peter Laidler wrote: Thu Mar 02, 2023 12:57 pm I am like you Tornado. I use a colourtune to set my mixtures. but I use my sensitive ears and stethescope to set the air intake.
......
I'll bet you a slab of beer that your carbs aren't balanced.
Suzy's were done by a professional using a listening tube, and a listening tube with a whistle in, and they weren't even close - I checked them with several different airflow meters afterwards.
Metric is for people who can't do fractions.
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Peter Laidler
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Location: Abingdon Oxfordshire

Re: Single to Twin SU Worth It?

Post by Peter Laidler »

Just PM'd you with my qualifications to say what I did
Tornado99
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Joined: Thu Dec 24, 2020 9:03 pm

Re: Single to Twin SU Worth It?

Post by Tornado99 »

Peter Laidler wrote: Thu Mar 02, 2023 12:57 pm I am like you Tornado. I use a colourtune to set my mixtures. but I use my sensitive ears and stethescope to set the air intake.

Nothing wrong with a refurbished - or known good - HIF44

What is your classic bike? Me too......
Cheers. Bike is a '74 Norton Commando. Came to me with a single Amal carb fitted. Ran ok, tended to be lean overall, bluing on the headers etc. Now has the original setup dual Amal's. Goes like stink.
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Peter Laidler
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Location: Abingdon Oxfordshire

Re: Single to Twin SU Worth It?

Post by Peter Laidler »

Hi Tornado, I'm another Norton Commando man. Glad to meet another man of taste. Have you tried an SU?
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