Were the comments re: Weber 45 DCOE for a 1500?? I'd love to hear what
anyboy else is running in a 45 on a 1275. I have 34 Main venturi, 35 aux
vent., 125-F2 main jets, 50-F9 idle jets. Any comments?? Geoff Branch
'74 Midget
-----Original Message-----
From: Daniel1312@aol.com <Daniel1312@aol.com>
To: ridleymj@bis.on.ca <ridleymj@bis.on.ca>; spridgets@autox.team.net
<spridgets@autox.team.net>
Date: Sunday, November 08, 1998 4:50 PM
Subject: Re: 1.5" SUs
>Hi Martyn,
>
>I do not agree that twins are better than singles. What matters is the
amount
>of airflow the engine receives (and requires) and with carbs the amount of
air
>the carb can flow be it a large single carb or two smaller carbs. Although
a
>twin 1.5 SU set up will flow a total of more air, on many A Series engines
you
>will get a better result with a single 1.75 (or maybe a single 2.0?). The
>only usual advantage of a twin SU setup over a single is better fuel
economy
>(gas mileage).
>
>Also, when talking about SU carbs it is perhaps worth clarifying which SU.
I
>mention this because the later HIF carbs flow more air than earlier HS
types.
>
>I am very acquainted with David Vizard's books, as well as Haynes SU manual
>and another book on SUs. I also have a library of other tuning books.
>Perhaps I can refer you to page 75 of the yellow edition of Vizard's A
series
>book where a table idicates airflow in cfm for a 1.5 SU H4 carb is 133, it
>being a reasonable assumption that two of these carbs make 266 cfm. The
same
>table indicates a SU HIF6 carb making 240cfm - only 26 cfm less than the
twin
>setup and I would suggest that the small gain of the twins might well
easily
>be lost on the manifolds.
>
>For myself I haven't run SU carbs in a decade but as I said before, from
what
>I have heard (some comments originating very close to Mr Vizard) the single
SU
>1.75 takes some beating.
>
>Further comment welcomed, especially when supported with dyno figures.
>
>Daniel 1312
>
>45 DCOE, 40mm main venturi (smaller sizes to prove it needed the 40mm
>venturis) 185 main jets, 55 pumps, 65 F9 idles - and the mixture bang on,
and
>engine taking full throttle in 4th at 2,500rpm if not lower with a MD286
>scatter cam (K&N air filter used to make sure small children are not sucked
>into the intake tracts)
>
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