289HP with C4 automatic

Onetim

New Member
Sep 14, 2018
26
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3
Farmington MI
Hi all new here, I have been running a actual 289hp in a A code fastback, with a early C4 automatic. The problem is a balance issue, lumpy idle that becomes a vibration issue at higher speed, like on the freeway. What is the correct flex plate offset weight, 28oz? or? Running the stock 3.0 gear, Engine is stock with thick dampner, internal offset weight, the engine was balanced during rebuild. I have had the drive shaft reblanced, and on car tire balancing to no effect.
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until 1981 all small block ford engines used a 28oz balance factor. after 1981 ford started switching over the 302/5.0 to the 50oz balance factor. 1981 is the year this change over started.