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[Fot] Was Weber carbs now SU Questions

To: Friends of Triumph <fot@autox.team.net>
Subject: [Fot] Was Weber carbs now SU Questions
From: Glenn Franco <gaf3@charter.net>
Date: Sun, 02 Nov 2008 11:26:41 -0500
I decided to go with  1 1/2" SU's for my Spit 1300 over Weber side 
drafts, but I'm having some issues with them.
The SU's are from an MGB and I rebuilt them with new jet assemblies, new 
gaskets and set the floats to a level position.
Per Joe Curto's advice I'm using early spitfire float assemblies to put 
them in a level position compared to the MGB.
The intake manifold is the British version made for 1 1/2" carbs. I'm 
running a race cam purchased from Ted at TSI and a Stahl header.

The problems I'm having are:

    * The front carb (last one in line to get fuel) starts to leak gas
      from the main jet when the engine is shut down. I'm assuming the
      float needle valve is not holding against fuel pressure.
          o The pump is a holley red electric and pressure is reduced to
            _3 1/2-4 psi_ at the pressure regulator. _Is that too much
            pressure for an SU?_
    * Another problem is resistance in the vacuum pistons from dropping
      completely. No matter how much I polish up the piston and bore It
      hangs up about 1/4' from the lowest positon. It does drop when I
      stroke the dashpot. This makes it hard to sych the carbs.
    * I'm running a bit on the rich side since the carbs were tuned for
      a 1.8L B engine but thought I could lean it out with the needle
      adjustments.
    * What viscosity is generally used in the dashpot? I used some
      10w30w oil I had around.
    * Is their any _online_ tuning guide for SU carbs out there?

Any advice would be appreciated
Thanks in advance
Glenn Franco
72 Spit racer running, working out the problems


Bill Babcock wrote:
> I agree, SU's are really pretty carbs, especially when they are  
> polished. I"m building a street TR3 and it will absolutely have SUs,  
> though in most other respects it will be Peyote in TR3 clothing.
> On Oct 30, 2008, at 3:06 PM, Steven Preiss wrote:
>
>   
>> I just like the look of the SUs in there. And the cork gaskets that  
>> don't
>> leak if renewed periodically, and the thumb sized jet nuts you can  
>> turn half
>> a flat with your hand to adapt to seasonal or elevation changes. And  
>> those
>> big aluminum dashpots with their own dipsticks! (Nobody would ever  
>> mistake
>> those for EFI!)
>> This, along with the rest of the package helps me keep in touch with  
>> my
>> agrarian roots, and makes me feel very happy.
>> STeve P.
>>
>> ----- Original Message -----
>> From: "Terry Stetler" <tlizzard@msn.com>
>> To: <fot@autox.team.net>
>> Sent: Friday, October 31, 2008 10:34 PM
>> Subject: Re: [Fot] Weber carbs
>>
>>
>>     
>>> .... once you are done, you are
>>> done.
>>>
>>>       
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>>     
>
> Bill Babcock
> Babcock & Jenkins
> Billb@bnj.com
> 503.936.7660
> www.bnj.com
>
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