The ol 451 hasnt been herself lately and have been busy,but tonight i opedned the cap and rust and carbon trials everywhere!!!!!!I spent two hours cleaning it up and now the exhaust is louder and car sounds meaner so im think'n no way..took it out and my god it pulls real hard..but also snagged one of the advance springs on my jacket i guess and lost one.A buddy brought some over that were a little stiffer but wondering being since i fixed the crazy spark patterns if i should put my weaker springs back in (when i buy some more)???But the real qusetion is how do you keep that sealed up cap vented???I swear you could run it under water..Thanks!

Buy a new cap its vented. Unless you have the old gm style with the points door?

run the lightest spring combo that will keep you just under the pinging point up thru the gears at WOT on your hottest/driest day. Want a vented cap to get the ionized air out of there which contributes to crossfire/carbon tracking and might check rotor phasing. Run it more often to keep an oil mist circulating to combat the rust EDIT & the heat from running will dry it out

Thanks for the replys..and the i'll try the lighter set again now that i have a consistant hot spark.

Here in the land of warm and dry (not lately) I found the same thing.

Mine is a rusty mess inside every time I look at it. I vented the cap by drilling small holes around the cap but problem continues. MSD tech said I did not drive the car enough.

The first guy to reply said they are vented now..have to check that out!

Since I had the raisin bran hood on my Dart...in the rain my distributor would get a bad crossfire from water getting sucked into the scoop and then dripping on my dizzy (it had a slant 6) I fixed it with vaseline on the lip of the cap/dizzy surface an a latex surgical glove stretched out over the whole cap. Problem went away....Looked funny in the engine bay though...