It sounds as though your distributor is connected to ported vacuum. If you connect it to manifold vacuum, then the ignition system will advance the spark anywhere from 12 to 18 degrees extra at low engine speeds. The motor may not like this and ping (detonate) when you try to accelerate.
Some engines are designed for full vacuum advance at low speeds, others are not. It depends on the camshaft, what kind of emission equipment is installed, the compression ratio, the piston deck shape, the condition and age of the engine, the gasoline octane rating, the transmission, the rear gear ratio, the air temperature, the list goes on and on and on. Without being there, I can't tell you for sure whether it can handle it. But if the motor pings with manifold vacuum, and it doesn't with ported vacuum, then it should only be hooked to ported. If it never pings AND the system is working correctly, then use manifold vacuum and see if the car performs a little better.
Do yourself a favor and test the vacuum pot on the side of the distributor to see if it's working like I described in my last post.
------------------
David
newbie #4153
