Re: [alfa] slow engine deceleration in off-throttle conditions -- ignition problem?

["Dean" <tessiedog@xxxxxxxxxxxxx>]

Sounds fair to me!
----- Original Message -----
From: "White Anthony" <anthony.white@domain.elided>
To: "Alfa Digest (E-mail)" <alfa-digest@domain.elided>
Sent: Tuesday, January 06, 2004 8:28 AM
Subject: [alfa] slow engine deceleration in off-throttle conditions --
ignition problem?


> Before Christmas, I dropped a rebuilt head on my 116.  At the same time, I
> took the Dellortos off my 105 (under restoration), and put them on the
116,
> as the Dellortos on the latter need rebuilding.
>
> The 116 Dellortos have an integrated vacuum take-off for the vacuum
advance
> on the ignition.  The 105 carbs do not.  In the interim I have blocked the
> vacuum advance mechanism on the distributor.  For the most part, the car
is
> running really well.  However, when lifting, particularly to shift gears,
> there is a pause of around half to three quarters of a second in which the
> engine speed will stay the same before the revs will drop, and even then
the
> drop is quite slow.  This is longer than it takes to change gears, and so
is
> providing a rather unpleasant sensation.
>
> Throttle return spring strength is good.  The carburettors didn't cause
the
> same problem on the 105, so I doubt that the problem is with them.
>
> I'm guessing it is an ignition problem -- specifically, that the
centrifugal
> advance mechanism on the vacuum advance distributor is weighted
differently
> from that in a mechanical advance only distributor, and so, without an
> appropriate vacuum take-off, isn't retarding the ignition when I lift the
> throttle.  However, it's been some time since I swotted up on ignition
> operation, so this is fairly uninformed speculation.  I do have a
mechanical
> advance distributor sitting in my workshop, so I'll try swapping that
later
> in the week.
>
> Until then, is anyone able to offer any advice or suggestions?
>
> Kind regards,
> Anthony White
> Wellington, NZ
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