In <Pine.NXT.3.91.960308135354.13483A-100000@mulberry>, Gen wrote:
>I'm holding off on calling Car Talk on this one because I think they'll
>call me a fool for even having a British car,
You should hold off on calling Car Talk on general principle. Much of
the time they are _wrong_, and I don't even think that they are
funny.....
>but I'm curious: my dad
>set the timing at Xmas in my 71 BGT dynamically, strobe light, whiteout
>on the mark etc., and it ran fine.
>so eventually took
>it to a shop where the guy said the timing was way off. He set it with
>the engine not running and said you shouldn't do it dynamically. DOes
>this mean my _Dad_ is wrong? I just want to know if timing should
>be set statically or dynamically and why. Dad said maybe the
>engine was worn enough (from a 74 B) that it shook or something in
>such a way that you couldn't set it accurately when running?
>
This is a tricky question. Depends on the condition of the engine and
how dear ol' Dad set the timing. First, unless the distributor is
totally hosed one can get the car running fairly decently stting the
timing statically. It may not be perfect, but shouldn't be off my
more than a few degrees, not _way_ off. The MGB distributor has a
very aggressive spark advance mechanism (both vacuum and mechanical) and
this needs to be taken into account when setting the spark
dynamically. I believe that the correct figure is about 14 deg BTDC
at 2000 rpm for dynamic timing (top of my head, don't go out and reset
your cars on that). Now, if you follow that spec (or at least think
that you do) you could still be wrong for a number of reasons, for
example, the mechanical advance springs are loose, the tach is not
right, you did not _disconnect and plug the vacuum advance when you
set the timing_ (and remember to reconnect it when done), the
distributor bearings are loose (gives you lots of wobble), the dwell
(gap) is set incorrectly, there is a hole in the vacuum advance
diphragm, etc etc. The list goes on.
The point is that you have a 25 year old (or so) car and things go bad
after a while. If everything is in perfect working order, then proper
setting of the spark can be done either statically or dynamically. If
not, neither will work so well, but static is probably more reliable
just to get the car to run. I wouldn't lose confidence in Dad's
skills and instincts just yet. He may have done just the right thing
but was foiled by the Ghost of Lucas......
A. B. Bonds
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