Since I am no longer certain if my mixture is set properly (and I'm getting
intermittent irregular idle), should I start with the carbs, or with the
timing? Perhaps the cold has something to do with it, but I'm getting
sometimes dark smoke (too rich, or another unrelated problem) or no smoke.
Thanks for the comprehensive info.
Charles
'74 Midget
'68 Sprite
cdsorkin@ix.netcom.com
Bloomfield, NJ
-----Original Message-----
From IfixMGs at aol.com <IfixMGs@aol.com>
To: cdsorkin@ix.netcom.com <cdsorkin@ix.netcom.com>
Date: Tuesday, February 01, 2000 10:24 AM
Subject: Timing without a timing light (LBC content a-plenty)
>Charles,
> I hope this is neither oversimplified nor stupiefying. It's an off
the
>cuff condensed version of a tech article I did some years ago for MG!
> Fastest idle is not necessarily the best idle advance. Most important
is
>the relationship between the static timing (engine off) and how much/how
fast
>the vacuum and mechanical advance comes on. Static timing, unencumbered by
>mechanical and vacuum advance establishes little more than how the engine
>starts, and idles. A timing tape, a known TDC reference, a handful of
>various advance return springs, and a timing light will go a long way to
>developing the right curve to make the most horsepower at any given rpm,
>without pinging or detonation.
> Timing tape and light aside, a better bet is a vacuum gage... providing
>you know that the carb/s mix is pretty close, begin by retarding the spark
>into the "red" 15"hg area, and advance it (cw) incrementally until you get
a
>good steady needle. I usu end the tuning session by richening the carbs a
>flat at a time (or with a Weber, 1/4 turn at a time) until I get that
>unmistakable 'putting' sound that indicates the mix is rich, and then lean
it
>till the vacuum goes high and steady. Once done, perform a piston lift and
>change mixture for best rise/decay.
> My rationale for the extra step is that vacuum is affected by a
number
>of factors. Advancing the timing to max idle may advance it too far for
>reasonably easy starting. Too much retard affects idle vacuum, off idle
>performance and cold starting. A slight vacuum leak, lean mix, or too much
>advance will also speed the idle up, and may go unnoticed until the weather
>warms up, and you note a rise in temperature. Richening the mixture
>eliminates the possibility that mixture affected the vacuum.
> The relationship between the crankshaft pulley and distributor is a
>2:1 ratio - for every full engine turn, the distributor turns 180 degrees
(it
>takes 2 full engine turns (one intake stroke and one powerstroke, so the
>distributor turns 1/2 eng speed to accomodate all cylinders thru 2 full
turns
>)
> If the crank index is set at 2 degree before Top Dead Center, and
>you rotate a loosened distributor 1 degree clockwise, obviously the crank
>doesn't turn, but the relationship between the point open event index
between
>the TDC pulley mark and the timing index marks has changed 2 degrees, so
the
>next time the eng is rotated around, the point open will take place at 4
>degrees before TDC.
> Mark Childers Union Jack Spares and Repairs VA Beach VA
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