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Re: Best Carbs for MG??? What about the manifold?

To: "Neil Cotty" <>, <>
Subject: Re: Best Carbs for MG??? What about the manifold?
From: "Lawrie Alexander" <>
Date: Sat, 1 May 1999 14:27:14 -0700

I'm afraid your multi-paragraph question lost me somewhere so I guess the
answer is - No, we can't talk about manifolds.

Actually, the theory you reference makes sense to me - a straight manifold
should permit better airflow at very high rpm. At low to moderate rpm, it
doesn't seem to make any difference. In fact, the turbulence seems to
improve low-end torque for some reason. Ever looked at the intake manifold
of a pre-war car? All twists and turns with, usually, one small and poorly
engineered carburetor sitting at ninety degrees to part of it. Those motors
usually made lots (comparatively) of low end grunt but had no capability for
revving very high.

-----Original Message-----
From: Neil Cotty <>
To: Lawrie Alexander <>;
Date: Saturday, May 01, 1999 8:26 AM
Subject: Re: Best Carbs for MG??? What about the manifold?

>Can we talk about inlet manifolds?! :)
>As SU manifolds are virtually straight shot into the siamese ports of the
>std B head, whereas a single Weber uses a bent manifold (long and short),
>what _tangible_ impact does this have on performance (airflow), both
>and power? Anything at all?
>If a Weber was choked to the same max. size as an SU what difference would
>there be? Would the bent manifold make it's impact felt in some way? There
>is no balance pipe (is there?), therefore I would *presume* that idle would
>be affected - ? I ask because I don't want to go to a single Weber (racing)
>because of the airflow issue, I realise Webers are more responsive, flow
>better (not inc. manifold) no piston etc, acceleration like an on/off
>switch - but I have read and heard that the bent manifold seriously
>interrupts the airflow - to the extent of making the better flowing Weber
>somewhat redundant on a std MGB head (but great on any 8 port head with
>webers).. A good example is a couple of local racers who are line ball with
>each other, one runs a 45 Weber, the other 1 3/4" SU's.. They choose only
>personal preference, looks, setup etc and both agree that the differences
>are subtle, the SU's providing slightly more torque, the Weber slightly
>power. Obviously length of the manifold alters this as well.
>On a std car, there is no way I'd buy a Weber. Simply because SU's are
>easier to maintain and setup for an amateur at home, only thing you can't
>yourself (After 2 hrs watching Lawries rebuild video :) is rebush the
>bodies. They are also the correct Carb for an MG. I even think a single
>looks naff on that huge inlet manifold (oO.. in my opinion - nomex donned
><G>) compared to a couple of SU's.. But I have to admit that two DCOE's on
>XFlow head look *seriously* excellent... <G> Drooolll..
>If you don't believe me that SU's look good - take a look at this pic of
>dual HS6 carbs on a Vintage Racer:
>Flame suit donned, filtering enabled, bunker readied.... <G>

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