The 71 monte used a "combination emission control system" for high gear deceleration and vacuum advance delay until high gear in automatics and 3rd and 4th in manual trans. It used a solenoid mounted on the driver's front of the carb. This solenoid had 2 vacuum lines on the back and a plunger that set the throttle. A vacuum hose comes off the front of the carb next to the solenoid,and goes to the solenoid. Then from the solenoid to the distributor. Using this setup, the dist will not get vacuum in park, neutral, first, or second. This is done to lower emissions. If you have a ported vacuum connection on the carb, (one that only gets vacuum when you oper the throttle slightly: not likely if your carb is original), I would hook directly from that to the distributor. That will give you better light throttle response.
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70 Monte, 454, auto. 70 Monte, 454+.030, 4speed.71 Monte, 350 beater. 71 Monte SS 454. 65 Corvette coupe 365hp.