My distributor weights won’t move

Question:

I have a question regarding an issue I found with my distributor. Not being exactly schooled in distributorship, I noticed that my 1976 Chevy Nova with the 305 cid V-8 has an issue with the distributor advance weights. When I was tuning my car with a new cap, plugs, rotor and cables I tried to move the advance weights with my finger to see if the springs had any life in them. To my surprise they did not budge. Is this normal? Does the distributor have to be removed for the springs to loosen up, or is this some type of other issue? At one point I dropped some penetrating oil on the springs and the weights, waited a few hours and gently tapped the weights with a screwdriver to see if I could break them free. The car seems to run OK, but I feel like the power is not there.

My other car, a 1979 Grand Prix with a 301 cid V-8, moves quickly while the Nova is lethargic even though the Nova has a bigger motor. Is it the stuck weights that are causing my woes? How can I break them free?

Answer:

You should be able to easily move the distributor advance weights with your fingers and the fact that you can’t indicates a problem.

In all likelihood, the weights are stuck to the distributor’s base plate because of a little bit of rust. The purpose of the weights is to advance the ignition relative to engine speed by mechanically moving the distributor’s base plate, hence the term “mechanical advance.”

Most vintage distributors rely on a combination of vacuum advance (also called initial advance) and mechanical advance. As the engine speed increases, the distributor turns proportionately faster and centrifugal force slings the weights outward on their pivots. The further out the weights move the more the ignition advances. The weight of the weights and the tension of the springs holding them determine how much advance is added over the engine’s range of speed. When the weights don’t move at all there is no mechanical advance and engine power and overall performance will suffer considerably.

You’ve already tried penetrating oil and some tapping and though you don’t say, I’ll assume the weights are still stuck. Aside from hitting them harder, maybe with a small hammer instead of a screwdriver, the best solution probably is to replace the faulty distributor with a new or good used one. Millions were made and they are readily available and relatively inexpensive.