Holley's instructions for the 4160 on my Buick say that too. (use timed/ported vacuum port) However, the Buick runs cooler with full vacuum. It does have a relatively mild street cam.

There's a lot of discussion about this issue . I found this article helpful: https://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor#Vacuum_advance


Gord 🇨🇦
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1954 1/2 ton 235 4 speed