Yes we see it on our 1500 and 1300 Spitfires. The inside to the intake
manifold is also carbonized, as though we are preburning the intake charge.
Not a good thing. You need to use some anti-reversion technique. Keep the
exhaust ports square, particularly the bottom, with the round exhaust pipe
being bigger or nearly bigger than the diagonal of the port. Also some
anti-reversion in the collector is supposed to help. Have some space around
the pipes, don't have them close to the collector walls.
Matt Matthews
Houston Tx.
> From: "Jack W. Drews" <vinttr4@geneseo.net>
> Reply-To: "Jack W. Drews" <vinttr4@geneseo.net>
> Date: Tue, 09 Apr 2002 06:10:49 -0500
> To: fot@autox.team.net
> Subject: standoff
>
> "Standoff" is the term used to describe the condition of a cloud of
> gasses hanging outside the inlet of the carburetors. We most often see
> it on SU and Weber-carbureted cars on cool, foggy mornings. It is
> usually attributed to sonic resonance in exhaust systems, where the wave
> bounces back and hits the exhaust valve at the moment of overlap.
>
> I had a TR4 on the chassis dyno recently that experienced a higher
> degree of this than I have seen before.
>
> Has anyone else experienced this and / or dealt with it?
>
> --
>
> uncle jack
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