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Moroso adjustable vacuum advance kit for 1975–1981 GM HEI distributors. This kit adds an adjustable vacuum-advance unit to HEI distributor setups, letting technicians tune vacuum-driven timing response for better idle and part-throttle behavior where vacuum advance tuning is desired. It installs on compatible HEI distributors from the specified model years.
Moroso 75-81 GM HEI Adjustable Vacuum Advance Kit
