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RE: measuring piston rise

To: <british-cars@autox.team.net>
Subject: RE: measuring piston rise
From: "Randall Young" <Ryoung@navcomtech.com>
Date: Sat, 22 Mar 2003 12:11:36 -0800
> I just realized that the HIF 6 in this application seems to have a
> vacuum port that is plugged off. If it leads to where I think it does,
> it gets the vacuum from between the butterfly and the piston, which
> means that it would "measure" the amount of vacuum that the piston is
> exposed to. Am I reading this correctly?

Unless a HIF is quite a bit different than the earlier models, the piston
gets it's vacuum signal directly from the venturi, which should be quite a
bit more than the vacuum between the piston and the throttle plate.

> I've been experimenting this week with using the green spring rather
> than the yellow (12 oz rather than 8oz), it seems to work pretty well,
> except for sometimes when trying to accelerate from a very low load
> situation, in which case the car just doesn't want to do anything,
> except possibly die.

Have you tried heavier oil in the dashpot ?  That's it's function, to richen
the mixture when you open the throttle suddenly.

> If I were a little less restrained on my
> sanity/time/research budget I'd experiment with a progressively wound
> spring on the carb piston. But if I were going to that much bother,
> I'd probably do better with a closed loop fuel injection system.

Why not use a needle with a faster taper ?

Randall

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