Distributor advance

["Westerlund, Ken" <kwesterlund@xxxxxxxxxx>]

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Hi Don,

In the "Old Reliable" book you discuss distributor modification for the
strip engine.  Are there any modification I should make to that
procedure for a 440 street only engine (mild cam, stock 1972
compression, headers, stock converter)?  E.g., not limit the mechanical
advance so much, or modify the advance curve differently?   

Thanks,
Ken 


-----Original Message-----
From: Don Dulmage [mailto:big-d@xxxxxxxxxxxx] 
Sent: Friday, January 07, 2005 9:46 AM
To: 1962to1965mopars@xxxxxxxxxx
Subject: dist vacuum


Yes the two are different. 
maniflod vacuum is drawn from below the throttle plates and is created
because the enginge is asking for more air than the carb is allowing in.
The limits the peed of the engine. 
Distributor vacuum on Mopars is venturi vacuum nowadays called ported
vacuum and is taken from above the throttle plates and is created by air
rushing by the hole or port provided. 
This vacuum ios a function of air speed through the carb venturi (or the
throttle body with FI) meaning the more air flows through thecarb the
higher the vacuum at this port will be which works out perfectly for the
dist advance since more air through the carb means more engine speed and
now higher vacuum at the distributor port and there fore more advance as
speed increases. . 
If you hooked the dist to the manifold vacuum port on the carb (often
the lowest port hysically) you would have max dist advance form the
vaccum advance unit at idle and none at full throttle because manifold
vacuum drops as the throttle is opened (no restriction from throttle
blades or at least very little) Rule of thumb is at idle there should be
no vacuum on the distibutor advance . It should only come when the
engine is reved. 
BTW most home done set up I see that came here for tuning had the
distributor hooked to the wrong port. 
If any more quetions feel free to email. I used to teach Engine Fuels
and Electrical at Provincial Trade School and firmly believe there are
no dumb questions ,only dumb answers.
Don
Author of
Return to Deutschland (True Adventure)
Old Reliable (Mopar)
http://stores.ebay.ca/Don-Dulmage-Enterprises
[Non-text portions of this message have been removed]

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