That was a chronic problem on that era Ford V8s. Friend of mine had a boat with twin Fords and I spent one Saturday morning in the mid 60s installing the "kit" that was available back then to solve the problem on both banks of both engines.
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Capt Bob
1969 Chris Craft 23 ft Lancer "Retriever"
260HP 5.7L MERC w/Volvo outdrive
Atlantic Salt Water Flyrodders, Seaside Park, NJ