Distributor blues

I live in Delaware. My 1969 chevelle (350 engine and trans) every-so-often has troubles with its distributor. When it rains, if the air is damp…the car will not turn over. Ususally a quick thump to the top of the distributor with a mallot does the trick. Thump, turn the key and whompf she fires up.
Getting tired of this process, we rebuilt the top end of the distributor and for nearly a year there have been no issues. Turn the key and go… now the car has resumed the old problem.
If its rainy or damp, you can pretty well bet that the distributor will need a smack if you want the engine to forward up.
What is causing this?

What does “rebuilt the top end of the distributor” mean? A distributor from a '69 350 should only need a rotor, a cap, and a condensor.
Did you also change the plug wires?
Do you have a good seal between the wire end boots and the distributor cap turrets?
Have you looked at the coil? I believe in the '69 the coil was seperate and mounted either on the inner wheel well or in the firewall. If there’s a problem there, a crack in the shell, a bad primary connection, or a bad connection with the hi-discharge wire to the distributor, that could be allowing a short to ground when wet.

Post back. I’m interested.

Points also I think s. m. . By the car not turning over do you mean it refuses to do anything when you turn the key to start?

For whatever reason - you are probably getting moisture up in the cap. A thump on the cap - shakes off some of the moisture - allowing it to start. Is it garaged? Car cover? Something is allowing moisture to get into the distrib.

Don’t know if you have or desire to go electronic. It is possible to get rid of the points…

Anyway - the following is a link to a NEW distributor - (takes points) fits a 69 Chevelle - 350 engine size; and has a lifetime warranty. Have a problem with it - they replace it free…

http://www.oreillyauto.com/site/c/detail/RPT0/GM10/02780.oap?year=1969&make=Chevrolet&model=Chevelle&vi=1038866&ck=Search_distributor_1038866_3698&keyword=distributor

I had a 72 Chevy 350 that would carbon track the cap badly enough to need replacing once a year. Never got mad enough to hit it with a hammer though.

I bet the problem is wires, plugs, dist cap. Also going to a High Energy electronic dist. would be great.

The next time it does this pop the distributor cap and note if there’s moisture on the inside of the cap. Engine heat can attract moisture just like a window pane sweating on a cold damp winter day.

Another potential cause (although dampness should not be a factor) would be if the wire into the distributor base plate has been rubbed through due to the advance mechanism moving. A tiny bit of contact between the bare spot and the distributor body could cause a problem that whacking may alleviate for the time being but I would hold off on the use of the mallet.

Bad wires or coil. I lived in De and had a 70 Nova. Cracked coil was my fix for the same problem.