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Re: [TR250] mechanical advance

To: Randall Young <ryoung@navcomtech.com>
Subject: Re: [TR250] mechanical advance
From: David <dmb993@earthlink.net>
Date: Sat, 18 May 2002 22:33:56 -0700
Cc: TR250 <triumphs@autox.team.net>
References: <NOEDJDCNFBCNELMBFNFEOEAHDBAA.ryoung@navcomtech.com>
User-agent: Mozilla/5.0 (Windows; U; Win98; en-US; m18) Gecko/20010131 Netscape6/6.01
Fascinating. I had no idea that the point cam is coupled to the distributor
shaft through the mechanical advance, and that this whole mechanism is
completely independent from the sliding point plate, and that the 
sliding point
plate is only used by the vacuum adv/retard. This makes perfect sense.
Thanks for the info Randall. :-)

On my distributor, freshly received from TREnterprises,
the 2 vacuum diaphragm are removed, and in their place is a threaded shaft
that's about 2.5 inches long, with a slider on one side and a thumb wheel on
the other. The thumb wheel is indexed for adv in one direction and retard
in the other. This mechanism rotates the plate that the points bolts to. 
Since
the mechanical advance is completely independent from the point plate, I
assume that I can use the thumb wheel to make small adjustments to the
static timing.

Thanks again,
David
'68 TR250 CD8124L

Randall Young wrote:

>> From what I can tell, the rotor spins
>> counter-
>> clockwise, as viewed from above, and the mechanical advance rotates the
>> points plate in a counter-clockwise fashion also. To me, this looks like
>> the
>> mechanical mechanism actually retards the timing since it delays
>> the opening
>> of the points relative to the position of the distributor. If someone
>> can fill me
>> in on this I'd very much appreciate it.
> 
> 
> David :
> 
> Are you talking about the mechanical advance, or the vacuum advance ?
> 
> The mechanical advance does not move the point plate at all, instead it
> moves the point cam relative to the distributor shaft.  Moving the cam
> farther CCW in relation to the shaft makes the points open earlier,
> advancing the timing.
> 
> Randall

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