Is the vacuum booster directly mounted to the master cylinder? I would think it is a divorced HydroVac as found on the older trucks. A working HydroVac will make noise and create a small disruption in idle quality, but you should have good power assist if all is healthy.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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