This is a story written by my favorite columnist, Peter Egan, in Road &
Track many years ago. It came from a collection of his columns printed by
Road & Track. I highly recommend buying it as he's truly a car guy with a
great sense of humor and always strikes a chord which is familiar to any car
crazy nut. I frequently laugh and smile when reading this book.
I dedicate this story to all those with SUs :)
Mike
A CARB NAMED SU
Last Thursday just when I was getting my life pretty much under control,
Associate Art Director Larry Crane walked into my office with a video
cassette tucked under his arm and said, "How would you like to see a two and
a half hour movie on rebuilding and tuning SU carburetors?"
"Two and a half hours of film on SUs? Who on earth would do such a thing?"
"My oId friend Lawrie Alexander," Larry said. "He's the sales manager at
Moss Motors, the MG specialists up in Goleta. He's a transplanted Brit who's
been working on English cars for years. Would you like to see the movie?"
"Love to," I said, not joking. "I'll take it home tonight." Now I realize
that most people, faced with a 15O-minute film in which the principal
characters are a veteran British car mechanic and two carburetors on a
workbench, would probably become slightly despondent, or even turn nasty and
unpredictable, possibly injuring themselves or others. But in my case, Larry
found a ready made audience. I've spent only slight exaggeration here about
half my life fiddling with SU carburetors and I was genuinely interested in
soaking up a little added insight from a real expert.
For those of you who have not had the pleasure of owning British cars, with
attendant weekends spent beneath the bonnets thereof, SU carburetors are
(were) the standard fuel/air mixing devices on Jaguars, MGs, Triumphs,
Healeys, etc, from time immemorial. SU stands for Skinner's Union, named
after George and Thomas Skinner, a pair of brothers who were in the
shoe-manufacturing business and invented this style of carburetor (with its
original leather- bellows arrangement) in 1905.
SUs are nice-Iooking carburetors, their most prominent feature being the
bell-jar shaped aluminum dashpot containing a piston and needle that rise
and fall with manifold vacuum, changing mixture with engine demand. In rows
of two or more, they have a way of making the most mundane engine look
relatively exotic, and it may have been the sight of those twin or triple
air cleaners under the hood that caused so many American youths and their
elders to plunk down money for their first English roadsters. It certainly
worked on me. Multiple SUs probably sold as many cars in this country as
wire wheels and bucket seats did.
Elegantly simple in principle and design, SUs wear their mechanical hearts
on their sleeves, so to speak; all three of their moving parts (piston,
throttle and choke) are visible with the air cleaners removed, and their
exposed workings give them the vintage look of a piece of 19th century lab
equipment, or possibly some early navigational instrument, like an
astrolabe - if an astrolabe could be made to hold gasoline and Ieak.
Though the SU carburetor is a pretty good design, it is not without its
faults, some of which may be directly responsible for so many of those
American youths mentioned above not owning British roadsters today. Throttle
shafts wear in their bushings, causing the engine to suck too much air
through the carbs, and, meanwhile, brass needles wear out and oval their
jets, as if to compensate. The real Achilles' heel, however, is the throttle
and choke linkage between two or more SUs. This system of rods, shafts,
clamps, levers and fulcrums is subject to wear, slippage and- worst of all
maladjustment by the owner. In fact, the really basic problem with every SU
carburetor and its Rube Goldberg throttle linkage is that it offers the
amateur mechanic more opportunity for doing The Wrong Thing than any
invention since the 4-masted clipper ship.
When I worked as a mechanic, it was amazing to see the variations of SU
carburetor maladjustment that came through the door. Air cleaners mounted
upside down, jets dropped to full rich or screwed up to full lean, rear
carbs disconnected from the fronts, pistons frozen in theirdashpots
and-strangest of all-piston dampers filled with STP rather than ATF or 20-wt
oil. Many people thought this was a competition trick.
They were wrong. And this is where Lawrie Alexander and his
two-and-a-half-hour video come in. Alexander stands at a workbench in front
of the camera and calmly, thoroughly explains how SUs work, shows you how to
rebuild all four styles of them (you can fast forward through those types
you don't care about) and then explains how to tune them on the car. The
amazing thing is he makes rebuilding SUs look so appealing and simple,
you're half tempted to go out and buy another British car, just to try out
his good advice and to get even for all those years you hadn't the faintest
idea what you were doing. The video costs $39.95, plus $3.00 for shipping,
from Milaw Productions, PO Box 742, Goleta, Calif. 93117. If you own an
English car, or even a Volvo with SUs, it'll be the best $42.95 you ever
spent. Okay, that may be an overstatement; I can't speak for sailors on
shore leave.
Students of high technology may object that using a VCR to rebuild an SU is
overkill, like using laser holographs to teach the lost art of roof
thatching. They are right, of course, and, sadly the SU is going the way of
roof thatch. It is a symbol in a way, of British cars. People who dislike
SUs on sight or can't be bothered fiddling with them will eventually be-
come disenchanted with English machinery in general, while those who delight
in tinkering, adjusting and setting right will find in the SU all of the
charm, texture and maddeningly eccentric logic that make the English car
worth troubling with, for those who understand. Or, until now, thought they
did.
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