Quick Facts: '67, 289 with factory(built-in) A/C
When accelerating hard, the vacuum is temporary lost to the a/c. The air will be coming out of the vents like normal, when you accelerate, it will blow to the floor for about 10- 15 seconds, then go back to the vents. Any ideas?

thanks

 

Manifold vacuum always drops off during load. The open throttle plates allow a lot of air to enter, so the suction created by the pistons is alleviated. A vacuum reservoir solves this problem, but I don't think a '67 used one.

I had a '38 Buick coupe with manifold vacuum wipers. If I stepped on the gas they would stop dead. I didn't drive in the rain.

 

Yeah, you are stuck with that phenomenon. Live with it. You are lucky to even have an air conditioner.