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My '71's 454" was still "chugging" after a cold start so I decided to drill two more 5/16" holes in its choke butterfly to give it a bit more air plus I backed off the choke housing one notch (now one notch lean). Engines with long duration camshafts and Holley carburetors are pretty picky on cold starts because of the poor low rpm efficiency and Holleys don't have a "choke pull off" like the QuadraJets have. Many of the Holleys used on the 1960's muscle car engines had holes in their choke butterflies for this reason.

When I cranked it early this morning it instantly started and fast idled but it did have a brief "chugging" moment that lasted a few seconds so I might have to enlarge the holes to 21/64".
 

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