Clay,
Back when I was debating how to put my extra HS-4s onto my Midget, I talked
to David Vizard, the guy who wrote the performance book on these engines,
and he said there was little advantage to dual 1.5 inch SUs over a single on
a good manifold, since in both cases, each cylinder could only "see" 1.5
inch of flow from a carb. He said this is why a single 1.5 makes more power
than dual 1.25s, because in dual 1.25s, each cylinder only "sees" 1.25
inches of flow. Sort of made sense, and the single 1.5 inch carb makes all
sorts of power, particularly when modified with the airflow "enhancements"
specified in the book. Since I had to file a needle to suit with mucho
testing, I was very thankful I only had to do one, as I can't imagine trying
to get two of them to match each other and work properly. Unfortunately it
was several years after I talked to him before I actually did the
conversion, and I lost track of him, so I couldn't ask him to help with my
problem. I think you all are helping me out in a big way though, and I hope
to have some answers tonight!
Bob
-----Original Message-----
From Clayton La Baw [mailto:clabaw at jpl.nasa.gov]
Sent: Thursday, January 03, 2002 1:23 PM
To: Mueller, Robert CDR; 'Peter C.'; David Littlefield; Mueller, Robert
CDR
Cc: spridgets@autox.team.net
Subject: RE: Weird Carb Problem
Bob -
I'm putting together a twin SU setup for my '67 Sprite using a pair of
H-4's from a Volvo 544. I got the SU Reference Catalogue from one of the
usual suppliers. It lists the carb's and component parts for most all
applications. There is a page listing float chambers for the H-4. They
are a) horizontal, b) 20 degree, and c) 30 degree types made. The float
chamber diameter gives you the "T" number. The casting numbers on mine
were AUC 3496 and 3495, indicating 2 5/16" diameter (T2) 20 degree
floats. I intend to adapt the original Volvo manifold to the Sprite.
According to the apps list, MGB's only came with HS-4 or HIF-4
CARBS. MGA's had H-4's, as did TF's, BN-4's, etc.
HS types come in horizontal or 30 degree; however, Burlen carries SU
adapters for 10 and 20 degree apps.
There is a ton of other neat stuff in this book; highly recommended, IMHO
regards,
Clay L.
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