Charles,
Start with the valves.
Jay Fishbein
"Charles D. Sorkin" wrote:
> 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@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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