Some applications of the SU carbs used this style of throttle disk.
The "Good Book" (Burlen Fuel Systems SU Reference Catalog) lists this
item as having an "Anti-stall Hole". Other styles include one with
"Anti-stall Notch" and "Overrun Emission Valve." I presume it limits
the minimum idle setting available, so that even with the disk fully
seated, some airflow is available.
> From: Richard Gosling <email@example.com>
> Date: Thu, 8 Nov 2001 11:17:31 -0000
> YES, that hole would have had an effect!
> NO, I don't think it's supposed to be there! No idea what it's doing there,
> but it may well have been your culprit. AFAIK (and there are plenty who
> know better), throttle discs should either be entirely plain apart from the
> holes in the middle that the screws pass through, or should have the
> (pointless and annoying) anti-run-on valve on one half.
> Richard & Daffy
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