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Old 01-09-2022, 12:10 PM
wbnapier wbnapier is offline
Senior Chief
Join Date: Sep 2017
Location: Encinitas, CA
Posts: 491

On a freshly restored tri-power I had a a similar problem after opening the outboard carburetors.

I had to add a heavier duty torsion spring (from a 4bbl) on the rear carb so that the outboard carburetor butterflies would close completely. You need sufficient spring pressure to return all the butterflies to idle.

Mike told me I can tweak the lighter duty spring to get some more strength out of it too.

1965 Pontiac GTO
455 w/ #48 Heads, '65 Tri-Power
Modern Muncie M22W
3.55 Rear Differential