Re: [Fot] SU carb smooth bore or leave rough?

[Phil Gott via Fot <fot@autox.team.net>]

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Still need the bridge!
We had a set of computune carbs with bridge removed on a 948 bug eye. It nee=
ded hand choking to start, wouldn=E2=80=99t 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 en=
ough that the fuel literally dribbles out of the jet. That=E2=80=99s apparen=
tly the only way to get them to run at most any throttle setting and engine s=
peed other than wide open.
There are a lot of ways to improve these carbs, but removing the bridge isn=E2=
=80=99t 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@autox.team.net> w=
rote:
>=20
> =EF=BB=BF
> Back in the day we thought we needed the bridge to help mix the incoming a=
ir with the fuel.
> Bruce
>=20
>> On Wed, Nov 25, 2020 at 12:04 PM David Gott via Fot <fot@autox.team.net> w=
rote:
>> Hi Mike,
>>=20
>> My TR4 came with a pair of Computune set up HS6=E2=80=99s that have had t=
he damper removed, and the whole bridge at the jet removed.  The jet stands a=
lone on its own, sticking up the height of the former bridge.  Also, the thr=
ottle 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 bushing=
s badly.  I=E2=80=99m 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 th=
em some day!  Anyone have experience running the Computune carbs? =20
>>=20
>> Dave Gott
>>=20
>>=20
>> Sent from Yahoo Mail for iPhone
>>=20
>> On Wednesday, November 25, 2020, 11:34 AM, DAVE HOGYE via Fot <fot@autox.=
team.net> wrote:
>>=20
>> I know that Huffaker does this.  I believe they also remove the damper oi=
l and or the damper completely and shave down the throttle shaft to almost n=
othing.  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 a=
nd engines quite regularly on their BMC builds. =20
>> Dave H.=20
>> =20
>> =20
>>> On 11/24/2020 12:41 PM Mike Harmuth via Fot <fot@autox.team.net> wrote:
>>> =20
>>> =20
>>> I was going over my race carbs (SU H4)and wondered if there's anything t=
o be gained  (or lost) by smoothing out the casting (before the jet)? I'm no=
t sure if it's designed (or left) that way to promote turbulence and better m=
ixing as the air flows over the jet or if polishing it down would help.
>>> =20
>>> I'd hate to trash a pair of good carbs before I get some answers.
>>> =20
>>> thanks
>>> mike h
>>> _______________________________________________=20
>>> fot@autox.team.net=20
>>>=20
>>> http://www.fot-racing.com=20
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mcast.net=20
>>>=20
>>>=20
>>=20
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>>=20
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>>=20
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>>=20
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto">Still need the bridge!<div>We had a set of c=
omputune carbs with bridge removed on a 948 bug eye. It needed hand choking t=
o start, wouldn=E2=80=99t run worth a darn below 3000 rpm. And if it stalled=
 in the grid, very likely, it needed a vigorous push start.</div><div>Post M=
ortem we learned that on these the float level needs to be set high enough t=
hat the fuel literally dribbles out of the jet. That=E2=80=99s apparently th=
e only way to get them to run at most any throttle setting and engine speed o=
ther than wide open.</div><div>There are a lot of ways to improve these carb=
s, but removing the bridge isn=E2=80=99t one of them unless you after pure W=
OT horsepower.</div><div>Phil Gott</div><div><br></div><div><br><br><div dir=
=3D"ltr">Sent from my iPhone</div><div dir=3D"ltr"><br><blockquote type=3D"c=
ite">On Nov 25, 2020, at 12:35 PM, Bruce Stutzman via Fot &lt;fot@autox.team=
.net&gt; wrote:<br><br></blockquote></div><blockquote type=3D"cite"><div dir=
=3D"ltr">=EF=BB=BF<div dir=3D"ltr">Back in the day we thought we needed the b=
ridge to help mix the incoming air with the fuel.<div>Bruce</div></div><br><=
div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, Nov 2=
5, 2020 at 12:04 PM David Gott via Fot &lt;<a href=3D"mailto:fot@autox.team.=
net">fot@autox.team.net</a>&gt; wrote:<br></div><blockquote class=3D"gmail_q=
uote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,20=
4);padding-left:1ex"><div>
Hi Mike,<div><br></div><div>My TR4 came with a pair of Computune set up HS6=E2=
=80=99s that have had the damper removed, and the whole bridge at the jet re=
moved.&nbsp; The jet stands alone on its own, sticking up the height of the f=
ormer bridge.&nbsp; Also, the throttle shafts are Steel, and very thin, only=
 picking up the throttle plate on one side.&nbsp; Alas, the steel has worn o=
ut the aluminum body and needs bushings badly.&nbsp; I=E2=80=99m sure they f=
low great, but without the bridge, probably tough to drive at anything other=
 than WOT. &nbsp; I bet part throttle modulation is difficult, but good dyno=
 numbers are sure to be there....&nbsp; I will try them some day!&nbsp; Anyo=
ne have experience running the Computune carbs?&nbsp;&nbsp;</div><div><br></=
div><div>Dave Gott<br><br><br><a href=3D"https://overview.mail.yahoo.com/?.s=
rc=3DiOS" target=3D"_blank">Sent from Yahoo Mail for iPhone</a><br><br><p st=
yle=3D"font-size:15px;color:rgb(113,95,250);padding-top:15px;margin-top:0px"=
>On Wednesday, November 25, 2020, 11:34 AM, DAVE HOGYE via Fot &lt;<a href=3D=
"mailto:fot@autox.team.net"; target=3D"_blank">fot@autox.team.net</a>&gt; wro=
te:</p><blockquote><div id=3D"gmail-m_4453025841764188289yiv4410313316"><div=
>
  <div style=3D"font-size:12pt;font-family:helvetica,arial,sans-serif;color:=
rgb(51,51,51)">
   <span style=3D"font-family:helvetica;font-size:12pt">I know that Huffaker=
 does this.&nbsp; I believe they also remove the damper oil and or the dampe=
r completely and shave down the throttle shaft to almost nothing.&nbsp; So, I=
 don't think you'd be trashing them, but I don't know what the dyno results a=
re either. As far as I know, they also replace head gaskets and engines quit=
e regularly on their BMC builds.&nbsp;&nbsp;</span>
  </div>=20
  <div style=3D"font-size:12pt;font-family:helvetica,arial,sans-serif;color:=
rgb(51,51,51)">
   <span style=3D"font-family:helvetica;font-size:12pt">Dave H.&nbsp;</span>=

  </div>=20
  <div style=3D"font-size:12pt;font-family:helvetica,arial,sans-serif;color:=
rgb(51,51,51)">
   &nbsp;
  </div>=20
  <div style=3D"font-size:12pt;font-family:helvetica,arial,sans-serif;color:=
rgb(51,51,51)">
   &nbsp;
  </div>=20
  <div id=3D"gmail-m_4453025841764188289yiv4410313316yqt59346"><div style=3D=
"font-size:12pt;font-family:helvetica,arial,sans-serif;color:rgb(51,51,51)">=

   On 11/24/2020 12:41 PM Mike Harmuth via Fot &lt;<a href=3D"mailto:fot@aut=
ox.team.net" target=3D"_blank">fot@autox.team.net</a>&gt; wrote:
  </div>=20
  <blockquote type=3D"cite">=20
   <div>
    &nbsp;
   </div>=20
   <div>
    &nbsp;
   </div>=20
   <div dir=3D"ltr">
    I was going over my race carbs (SU H4)and wondered if there's anything t=
o be gained&nbsp; (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 be=
tter mixing as the air flows over the jet or if polishing it down would help=
.=20
    <div>
     &nbsp;
    </div>=20
    <div>
     I'd hate to trash a pair of good carbs before I get some answers.
    </div>=20
    <div>
     &nbsp;
    </div>=20
    <div>
     thanks
    </div>=20
    <div>
     mike h
    </div>=20
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