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[Spits] 79 Spitfire with SU carbs

To: spitfires@autox.team.net
Subject: [Spits] 79 Spitfire with SU carbs
From: David Woerpel <dwoerpel@wi.net>
Date: Tue, 26 Jun 2007 17:43:27 -0500
Hello,

I am helping a friend with a 1979 Spitfire 1500.  He's removed the 
Zenith and installed 2 S.U. HS4's.  I'm one of the masochistic types 
that likes working on SU's and have no problem with the H4's on my MGA 
or H1's on the Bugeye Sprite but this problem has us stumped.

The car has been desmogged, the head lightly shaved (I don't know how 
much) and the rest is stock as far as we know.  It was running happily 
and he decided that he wanted SU's.  The carbs are set correctly. We 
started with the jet adjusting nut at 12 flats down (yes, they are 
centered).  The float levels are at 3/16", oil in the dashpot (1/2" 
above tube).  The car starts and runs on choke and the pistons rise 
equally but when the choke is gradually reduced after, 3-5 min., it 
starts to stall.  Add choke; it runs.  Push off the choke and it wants 
to die.  When we tried hand manipulating the throttle it occasionally 
coughs back through the carbs and dies.

The owner had ordered a new mechanical fuel pump which we installed.  It 
ran better off choke momentarily but then fuel poured out both float 
bowl overflows.  I know the mechanical pump isn't putting out too much 
pressure so I'm suspecting the float needle and seat.  New rubber tipped 
ones are on order.  The coughing back through the carbs makes me suspect 
timing but when it runs it's pretty smooth.  Just for kicks, what are 
the timing specs for a 79 1500?  He has no manual and mine are for my 
above cars.

Any suggestions would be very helpful.  Thanks in advance.

Dave
59 :{)
59 MGA 1500
05 MCS
Burlington WI
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