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Re: SU Carbs

To: Mark Dent <stickerman@home.com>, datsun-roadsters@autox.team.net
Subject: Re: SU Carbs
From: Kyle Hagemann <kyle@sonic.net>
Date: Mon, 18 Jan 1999 11:28:11 -0800
At 01:28 PM 1/18/99 +0000, You expounded thusly:
>This may sound like a strange request but I need a SU carb. I do not
>need it to work though. I just want to take it apart so I get a better
>idea of these things. I think I can get a better idea with a visual but
>I don't want to take mine apart because I won't be able to put it back
>again! Free is preferred but I can pay too.
>Mark

Whoa!  That does sound strange...  You might be better served by getting a
service manual...  The Nissan manuals all have a very good section on the
theory of operation of the SU carb.  It'll explain the overall theory,
including the variable venturi, as well as the functioning of each part.
You sound a little scared of your SUs - don't be!  They are super-simple.
Basically, there's three parts other than the carb body:
a)      the dashpot piston, which holds the needle. It rises and falls, based on
engine vacuum, richening or leaning out the mixture as it goes.
b)      the throttle shaft, butterfly valve assembly.
c)      the nozzle - also called the jet.  The needle rises and falls inside the
nozzle when the piston moves.  The nozzle will move down when the choke is
engaged to richen the mix for cold running.

a) is really simple, a piston in a chamber - take it apart and have a look
- nothing to screw up there!  b) is really complicated and should never be
messed with - there's several little linkages for the chokes and whatnot,
and it's a PITA to get back toegether. c) is just as simple - a tube that
slides up and down in the carb body based on the choke and adjuster.  To
get the nozzle assembly apart, though, you really need to remove the carb
from the car.

These carbs can be completely overhauled with a can of carb spray and a
couple gaskets!  E-Z!!!!

Get a manual, read it, and fool around with 'em - it'll work out well!

Another thought is Scott Bruning's SU video...  for the $15 or $20 he
charges, it's well worth it...

Kyle
     ____  Kyle Hagemann, Born-Again Grease Monkey From Beyond
 _.;(____\____    72 240Z, L28, 5spd, poly, etc. - The Z-Beast
|  _ |   |  _'@`, 66 1600, Daily Driver - For Sale! $3,250 /bo
`-(@)------(@)-;  69 2000, U20, goes like stink - no name yet!
-_-_-_-_-_-_-_-_- 84 Maxima, it's a bulletproof tank - Mr. Max
http://www.sonic.net/~kyle 240Z tech info, Win95/8 theme, etc.
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