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Re: C4 upshift

To: land-speed@autox.team.net
Subject: Re: C4 upshift
From: ARDUNDOUG@aol.com
Date: Sun, 23 Jun 2002 00:11:29 EDT
In a message dated 6/22/2002 7:05:31 PM Pacific Daylight Time, 
saltracer@hotmail.com writes:


> Thanks so much for the accumulated advice on our timing on the flathead. We 
> went to a local drag strip today for some test and tune and the car runs 
> strong, but we have a problem with the 2-3 upshift on the C4 automatic. It 
> doesn't shift right away and will let the engine rev quite a bit before 
> 
Phil,
    What's been done to modify the tranny? I presume that it still has the 
stock valve-body? I use manual valve-body (driver makes all shifts) C-4's in 
both my LSR and drag cars, so I don't have any hands-on knowledge of the 
stock C-4 shift points. 
    I do believe however that on a stock C-4 the shift points are controlled 
by vacuum from the intake manifold, and possibly also from centrifugal input. 
In a multiple carb setup or IR injectors the manifold vacuum would be either 
low or non- existent, depriving the tranny of it's shift-point sense or 
giving it the "low vacuum" signal that full throttle gives, delaying the 2-3 
shift.
    I'm just guessing. Hopefully someone with experience can enlighten us.
    Perhaps Tom Bryant can enlighten us. He deals with stock tranny's in his 
everyday business.......Ardun Doug king

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