MGA distributor vacuum is supplied from *outside* the throttle. That is why you
get '0' at idle and a reading on acceleration. If you want to measure your
intake manifold vacuum you must tap into the manifold and not the line that
goes
to the distributor. Once you do this your vacuum guage will act normal. I don't
recall the exact readings but normal is about 15-20 inches Hg at idle, dropping
on acceleration and higher on deceleration. BTW, there is a spot to allow you
to
tap into the manifold (didn't mean to imply you should drill a hole and tap
it...). Remove one of the studs holding the "tappet clearance" plate. I don't
recall the thread size, you might need to make a fitting if your JCWhitney
guage
doesn't include anything that fits.
Eric <ejrussell@sprynet.com>
Bridgewater, MA
>Date: Sat, 19 Sep 1998 19:18:57 -0500
>From: Sam Perera <sperera@blkbox.com>
>Subject: MGA and a vaccum gauge
>
>For fun, I have started to add an ammeter and a vaccum gauge to my 1600.
>I'm into my project currently and the mechanical vaccum gauge ( bought
>from JC Whitney ) has been hooked up.
>
>Can anyone tell me what reading it should be so I'm at the perfect
>setting. The needle shows a value as I accelerate and return to 0 at
>idle. Is this correct ? My distributor is rather old and the vaccum unit
>looks even older. Hoever, I've never had any trouble with the car
>lately.
>
>Thanks.
>Sam
>
1600 MGA MKI Roadster
1500 MGA Coupe - needs restoring
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