Greetings All,
Last night I was adjusting the timing on my '77 Spitfire when I made what
is probably a rather basic observation. With the distributor vacuum pipe
disconnected I notice that my timing changes as RPM's increase. Thus while
at 850 rpm I can set it at the recommended 10 degrees BTDC it climbs to
almost 16 degrees BTDC as RPMs increase.
While this in itself did not seem all that unusual I then noticed that when
I connect the vacuum line back up to the distributor that it essentially has
no effect although it is pulling air. I still go from 10 degrees to about
16 as RPM increases. I theorized, perhaps incorrectly, that the purpose of
the vacuum connection on the distributor would be to maintain the
recommended 10 degree timing regardless of RPM.
Is my theory flawed and everything is as it should be or is something
misfunctioning? If the later I would guess that the defunct component is
the vacuum
unit attached to the distributor. Does this sound reasonable?
Any insights??
Regards,
Mike Israel
mike_israel@merck.com
77 Spitfire
86 XJ6 (still won't start)
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