Sometimes when I drive my 74 Mav: 200 I6, 3sp manual, in the rain, the engine runs very rough. Something under the hood is getting wet. Is it the distributor or what?
Plug wires are bad.Replace them as well as cap/rotor.Look at your plugs too may be time to replace those as well.
Yeah could be getting under the cap or it has a crack in it somwhere.Pull it off and look for what appears to be a pencil line inside the cap(carbon tracking) that usually indicates a crack in the cap.Also make sure none of your plug wires are contacting anything that will burn them,this will give you the same problem.Even if the wires are new,if you cooked one it will leak.I assume you replaced the coil wire as well,if not,do so.
My first thought was plug wires. My first car was a 12 year old (at the time) 65 Mustang, and it still had the factory plug wires. It would die driving along a 60 mph if it started raining! Changed the plug wires ... problem solved. I would bet that maybe you are getting some cross-firing on a couple of wires and that the rain brings it out. This can happen on nearby cylinders that run parallel to each other. Make the wires cross each other twice if you can not route them away from each other. I don't know if I am being clear enough here. Perhaps a pro mechanic could explain this better how to make this work. Also, shoot the whole ignition system with WD40 and that helps keep the moisture out. One more thing ...There is a rubber strip that came on the firewall to seal the gap between the cowl and the hood. Many of these rot and fall off never to be seen again. If yours is gone, it may help a lot to replace it.
My guess would be plug wires. Just because they are new doesn't mean they are any good. There is a lot of cheap junk being sold out there.
in my olds i had to put some grease around the dizzy cap. that was just a temporary fix though. it seemed to die after comming to a stop in the rain
An old mechanics trick that always works is to start the engine in the dark and look for the light show. Keep your hands back from the fan and rotating assemblies though...you won't see those in the dark! Anyhow, if the wires are the culprit you will see blue arcing where it's happening. It could be near the plug ends or on the distributor side, or even in the middle of the wires where they come close to metal or cross each other.
His car is a nice, all original, very low mileage car. The firewall seal was still intact, at least when I saw it last year. The coil appeared original then, also. John, is the points and condenser still original?
If the coil is original, I would look at that really hard. It might be cracked and I imagine that high humidity could mess with it if that was the case. I may have a good original for a 302 still around here if you need one. I switched my whole points/condensor and coil over to Pertronix stuff. A great way to convert to electronic ignition and a very worthwhile change. It still looks very factory because all the goodies fit under the distributor cap. Points are only good the moment you put them in and then it is all downhill from there.
