Interesting...
I assume that by this you are implying that there should
pretty much be a constant "low frequency" vaccuume on
the intake port, and no variation at a higher frequency..
I did a compression test about a year ago and got around 110-120
per cylinder. I'll try the vaccuum guage and see what it
says.
Thanks! :)
Dave
----------
From: Robert Allen
Sent: Monday, March 03, 1997 1:11 AM
To: David Hall
Subject: Re: Vaccuume Advance
Sounds real odd. Have you done a careful compression test? Can you hear
the "huffa huffa" out the carbs? Connected a vaccuum gauge? Is there
variation there?
Bob Allen
David Hall wrote:
>
> Hi All!
>
> I have recently removed the air pump, gulp valve, etc from my 72 GT. Now,
>the only
> thing hanging off of the intake manifold is the vaccuume advance for the
>distributor.
> At idle, the vaccuume advance is acting like a speaker and humming (buzzing?)
> My
> guess is now that the gulp valve is no longer attached, there is a stronger
>linkage
> between the intake manifold pressure and the vaccuume advance. If I remove
>the vaccuume
> tube and place my thumb on it I can feel the thupa thupa thupa on top of a
>constant
> vaccuume. (Electrical analogy - a sine wave riding on top of DC.)
>
> I placed a timing light on it and did not notice the timing jumping around,
>so I am
> guessing that the magnitude of the variation in pressure is not enough to
>change the
> actual advance. However, the noise is annoying, and it doesn't seem like it
>would
> be good on the vaccuume unit.
>
> Has anyone run into this problem? My guess is that I need the equivalent of
>a low
> pass filter. Either a large vaccume resivoir, or perhaps a restriction in
>the line.
> Any ideas?
>
> Thanks!
>
> Dave (waiting for a new MG in the states) Hall
> http://www.pacifier.com/~dlhall
> 72 MG BGT
> 74 Midget
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