I currently have a 1275 with twin 1-1/4 su's. My question is would a single 1-3/4 do the same or better job?
I have a mate who is in to datsons and he thinks his got a couple of 1-3/4 up the back of the shed that he'll never use, he uses webbers.
On the plus side one su is easier to tune then two....

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I have an Addiction just not the time.......
1966 Morris Mini Deluxe http://www.ausmini.com/forums/viewtopic.php?t=80459
1968 Morris 1100 viewtopic.php?f=3&t=101555

The A series book by David Vizard says that the induction pulsing of these engines is such that only one cylinder draws on the single carb at a time, so it doesn't make much difference if there is one or two.
So then you can say that a single 1 3/4 would flow better that twin 1 1/4, assuming the manifolds and air filters are similar.

That's my interpretation anyway

Makes sense to me too, thanks for the reply

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I have an Addiction just not the time.......
1966 Morris Mini Deluxe http://www.ausmini.com/forums/viewtopic.php?t=80459
1968 Morris 1100 viewtopic.php?f=3&t=101555

I have seen a good road S motor give 90+HP (at the crank) on GR's engine dyno with twin HS2s, if you want more than this IMO you need either a pair of HS4s, a single HS6 or HIF44, or a Weber/Dellorto.
My2c,...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

the MG lads answer this question often.

cross section of the twin hs2s is tiny tiny tiny bit more than HS6, so essentially the same, however flow wise hif44 beats hs6 by a little.
i would think it would come down to the flow on the manifolds.

Thanks guys the answers were similar to wgat i was thinking. I need to rebuild my twins so I thought I'd explore the opitions and the 1-3/4 just come up. I am trying to stay away from the weber until its on the road.

_________________
I have an Addiction just not the time.......
1966 Morris Mini Deluxe http://www.ausmini.com/forums/viewtopic.php?t=80459
1968 Morris 1100 viewtopic.php?f=3&t=101555