Not seen any replies to this either ...
Don't know how US smog kit or manifold vacuum take-off affects things but on
a UK spec car advancing the timing will increase the speed till a misfire
causes it to start reducing again. The onset of this misfire is used as a
marker point when tuning by vacuum gauge, the timing is set at 3/4in Hg back
from it.
PaulH.
-----Original Message-----
From: Mike Lishego <mikesl@tartan.sapc.edu>
To: MG List <Mgs@autox.team.net>
Date: 27 January 1999 00:44
Subject: More on timing
>Howdy all,
> I noticed a strange problem with my MGB. It had a little
>stumble at low rpms under load until it fully warmed up. No matter
>where I put the choke, it still acted up. Oddly enough, it just
>started this week. I thought I might have some carbon build-up, so
>I wound the car through the gears to no avail.
> To make things even weirder, I had a funny little problem where
>my idle speed while on choke would be about 1000 rpm. Once the car
>was warm and the choke was out, it jumped to 1500. The engine
>wasn't racing, just idling high. I checked multiple times to be
>sure that my choke linkages were in the right places and my mixture
>was set right, but I found no mistakes.
> Then today I decided to turn the timing back a touch to drop the
>idle. I did, and the car was a turd. I felt that I'd be better off
>with a high idle and power than otherwise. I loosened the bolt on
>the dizzy with the car running and started advancing the timing. I
>turned the dizzy past my original point, and was astounded to hear
>my idle drop!
> I clamped the bolt down and drove the car - it ran better than
>before, but not much. The most noticeable effect was a slight
>backfire when downshifting - of course, this could be due to small
>exhaust leaks. So, I'm wondering, is there a point in the timing
>where the idle will be at it's highest, and after that point the
>idle will drop, regardless of whether advancing or retarding the
>timing? On the same thread, can retarding the timing too much cause
>the starter to lug when trying to start a car when it's warm?
> FWIW, I just went out and tested the car while it was cold. The
>car idled at about 1200 on choke, 900 rpm without. I guess that's
>pretty close to factory specs; if I remember right the manual says
>something like 1200 choke/1000 w/o. The car also warmed up much
>faster than normal too - keep in mind that it's 40 deg. F right now,
>so morning temps aren't going to be much colder.
> The important thing is that my timing changes appear to have
>fixed any ailments I might have had. Can increasing the timing
>enable a car to burn _more_ fuel, or does it just enable the engine
>to burn it _more effectively_? I'd like to know why this stuff
>happened. What do you folks think?
>
>Michael S. Lishego
>http://www.geocities.com/MotorCity/Speedway/3706/
>
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