[Fot] SU carb smooth bore or leave rough?

[Phil Gott]

Still need the bridge!
We had a set of computune carbs with bridge removed on a 948 bug eye. It needed hand choking to start, wouldn’t run worth a darn below 3000 rpm. And if it stalled in the grid, very likely, it needed a vigorous push start.
Post Mortem we learned that on these the float level needs to be set high enough that the fuel literally dribbles out of the jet. That’s apparently the only way to get them to run at most any throttle setting and engine speed other than wide open.
There are a lot of ways to improve these carbs, but removing the bridge isn’t one of them unless you after pure WOT horsepower.
Phil Gott



Sent from my iPhone

> On Nov 25, 2020, at 12:35 PM, Bruce Stutzman via Fot <fot at autox.team.net> wrote:
> 
> 
> Back in the day we thought we needed the bridge to help mix the incoming air with the fuel.
> Bruce
> 
>> On Wed, Nov 25, 2020 at 12:04 PM David Gott via Fot <fot at autox.team.net> wrote:
>> Hi Mike,
>> 
>> My TR4 came with a pair of Computune set up HS6’s that have had the damper removed, and the whole bridge at the jet removed.  The jet stands alone on its own, sticking up the height of the former bridge.  Also, the throttle shafts are Steel, and very thin, only picking up the throttle plate on one side.  Alas, the steel has worn out the aluminum body and needs bushings badly.  I’m sure they flow great, but without the bridge, probably tough to drive at anything other than WOT.   I bet part throttle modulation is difficult, but good dyno numbers are sure to be there....  I will try them some day!  Anyone have experience running the Computune carbs?  
>> 
>> Dave Gott
>> 
>> 
>> Sent from Yahoo Mail for iPhone
>> 
>> On Wednesday, November 25, 2020, 11:34 AM, DAVE HOGYE via Fot <fot at autox.team.net> wrote:
>> 
>> I know that Huffaker does this.  I believe they also remove the damper oil and or the damper completely and shave down the throttle shaft to almost nothing.  So, I don't think you'd be trashing them, but I don't know what the dyno results are either. As far as I know, they also replace head gaskets and engines quite regularly on their BMC builds.  
>> Dave H. 
>>  
>>  
>>> On 11/24/2020 12:41 PM Mike Harmuth via Fot <fot at autox.team.net> wrote:
>>>  
>>>  
>>> I was going over my race carbs (SU H4)and wondered if there's anything to be gained  (or lost) by smoothing out the casting (before the jet)? I'm not sure if it's designed (or left) that way to promote turbulence and better mixing as the air flows over the jet or if polishing it down would help.
>>>  
>>> I'd hate to trash a pair of good carbs before I get some answers.
>>>  
>>> thanks
>>> mike h
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