<div dir="ltr">Thanks to everyone for their insights. I think I'll just look for any obvious rough spots but mostly leave well enough alone.<div><br></div><div>mike h</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Nov 25, 2020 at 4:52 PM Enquiries Road & Track <<a href="mailto:enquiries@roadandtrack.net.au">enquiries@roadandtrack.net.au</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">I have had a few goes at shaving throttle shafts with very mixed results..typically fracturing where they meet the carby body. if you planned to change them routinely, thats not such an issue<div><br><div>Some recent flow bench work leaves me wondering completely about the wisdom of any of this without real-world testing<br></div><div><br></div><div>We found some head/intake arrangements where the air flow was too high in certain places and we had to dimple the port to slow it down. Sometimes, just enlarging the port does not work as intended</div><div><br></div><div>The very best SU research ive seen was done by David Vizard . There are plenty of on-line references to his work, but if anyone can't find what they want, i can scan relevant parts of his text book (tome) on tuning BMC A series engines. Ive used his analysis on various shapes of ram tubes for many years</div><div><br></div><div>of far more importance seems to be the distance from the valve to the throttle plate, with the ideal varying considerably with the RPM range being used. As a general comment, it seems like many folk have it far too long </div><div><br></div><div><div>I have proven that fiddling with the damper in a SU has a dramatic effect on throttle response, and not always what you think. i'll offer the comment that its very engine set-up specific. Sadly, this aspect is all-but impossible to test on a conventional flow bench</div></div><div><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><br></div><div>Terry</div><div>Australia<br><br></div></div></div></div></div></div></div></div></div></div></div></div></div></div><br></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Nov 26, 2020 at 2:35 AM DAVE HOGYE via Fot <<a href="mailto:fot@autox.team.net" target="_blank">fot@autox.team.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
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<span style="font-family:helvetica;font-size:12pt">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. </span>
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<span style="font-family:helvetica;font-size:12pt">Dave H. </span>
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On 11/24/2020 12:41 PM Mike Harmuth via Fot <<a href="mailto:fot@autox.team.net" target="_blank">fot@autox.team.net</a>> wrote:
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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.
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I'd hate to trash a pair of good carbs before I get some answers.
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thanks
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mike h
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