Tom
You need to be careful with your spring replacement. The Ford Parts
manual lists the springs as Primary and Secondary; they are 2 different part
numbers and 2 different springs. The Primary spring has round ends, this
spring controls the initial part of the advance curve and has to bring the
mechanical advance back to zero at idle. The Secondary spring has oblong
ends and is part of the advance curve at higher rpm.
If you replaced only the primary spring with a lighter one and the
initial timing went up; then either the spring is way too light or you need
to move the spring mount tang out to increase the spring tension to bring
the mechanical advance back to zero. If the zero mechanical advance at
idle is not maintained in the distributor your timing will be floating and
changing and you will never get to a good tune up position.
Sometimes the best thing to do is nothing; just put everything back
to what you started with and be happy.
Ron Fraser
-----Original Message-----
From: owner-tigers@Autox.Team.Net [mailto:owner-tigers@Autox.Team.Net] On
Behalf Of Thomas Witt
Sent: Thursday, February 01, 2007 3:08 PM
To: tigers@autox.team.net
Subject: Re: Timing
Steve,
>>>While a change in springs can influence the rate of mechanical
>>>advance,
the total advance is controlled by the weight slot stops.<<<
Yes, that is true, and part of the "potential" problem. I will try and
illustrate (values are hypothetical): Stock springs: Initial advance 10
degrees Centrifugal advance (at crank) 26 degrees Total Advance 36 degrees
Softer springs (with distributor NOT moved from previous settings): Initial
advance becomes 14 degrees (extra 4 degrees come from the weaker springs
allowing the weight to add centrifugal timing advance - even at
idle)
Centrifugal advance (at crank) 26 degrees
Total Advance 36 degrees (which is where I think your logic is leading you)
BUT, if the advance was desired to be reset back to the Initial 10 degrees,
the Total would then become 32 degrees. In essence the weaker springs use 4
degrees of the previously available 26 degrees. Thus, the slot only
"effectively" provides 22 degrees. So, if it was desired to add softer
springs, but correct the initial advance back to it's original setting the
(I'll say potential) Total timing could be compromised. Potential - in that
some softer springs might not create the problem, but others, given how soft
the springs are and/or how heavy the weights are, can at times create the
issues I have presented. At least I have experienced it. Granted I do not
purchase application specific springs, but grab what I've got and "tinker."
Tinker - which typically involves spending a whole day and often ultimately
deciding I should have left well enough alone! :-(
Tom
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