Randall,
My distributor only has vacuum Retard and centrifugal advance. I
disconnected the vacuum retard when I was initially trying to get the engine
running after a rebuild. It seems to run okay, so I didn't reconnect it.
Should I reconnect the vacuum retard and advance the timing so they balance
at idle, but have more advance at greater throttle positions?
Alan Harris
69 TR6
above in ref to:
Date: Fri, 15 Oct 1999 08:04:51 -0400
From: "Jack Brooks" <brooks@belcotech.com>
Subject: RE: Vacuum advance - Clarification
Randall,
The bottom line is that at idle, the vacuum advance is pulled in by the high
vacuum in the inlet manifold changing the timing. When you open the
throttle, you let in more air and bring the vacuum in the manifold closer to
zero, allowing the vacuum advance to move back to it's static position. So,
the question is whether the engine is advanced or retarded as the vacuum
decreases or increase.
Listers, can anyone shed some light on this issue?
Thanks,
Jack Brooks
1960 TR3A
1974 Norton 850 Commando
Hillsdale, NJ
> Jack :
>
> I'm not sure if I said one of those things that "just didn't sound right"
> <g>, but I think Barry glossed over the point that most if not all auto
> vacuum advance systems do NOT advance the spark at idle (unless the engine
> is overheated). Efficiency at idle is not a concern (it's 0 by
> definition),
> and a retarded spark makes for a smoother, more stable idle speed. Also,
> for most engines, the centrifugal advance is no longer working at idle, so
> the idle timing needs to be retarded for the slowest possible speed, not
> just the nominal idle speed.
>
> Randall
> 59 TR3A daily driver
>
>
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