View Full Version : dist cap corrosion ARGHH!

08-14-2005, 03:21 PM
I am thoroughly fed up with this whole ionization of air thing that causes excessive corrosion in my distrubtor cap. im running a mild 355 motor in my elcamino. 450 lift cam, edelbrock air gap manifold. nothing facny really. i have the full MSD ignition system. 6A box blaster 2 coil and the pro-billet dist with no vac advance. the first time i had this problem i replaced the then "new style" dist cap, with a vented one. i still have had the same problem since. this is getting quite old. as a matter of fact it is this very problem that made me yank the car off the road and start driving something else. well now im ready to get it running again and i just dont understand how to solve this problem. my drag car has the old style cap on it and while it isnt driven regularly i cant remember the last time i had the cap off since the motor was built 3 years ago. same thing with my friends car, he ran the same old style cap and never had issue. simple logic would tell me the old style cap is the answer but i sell way too many of these things at my speed shop with little to no complaints to make me think that the new design is at fault. what gives? and if the only answer i get is to drill holes in my cap, im yanking the whole thing out and going back to HEI

08-15-2005, 11:40 AM
Check the bottom side of your oil fill cap. Are you getting a thin film of water or milky substance? If so you might have to get a better pc breather system. Water vapor from the engine will vent out of your distributer and collect in you cap.
This is worst if you live in a real humid area, don't drive the car offen or run a 160 t stat. Make sure the hood seal is ok and water doesn't collect on the intake cause condensation inside the cap.

David Pozzi
08-15-2005, 12:02 PM
Things that would make it worse are high resistance in the plug wires, excessive plug gap, or high compression.
Are you just seeing crud on the terminals or is it causing the engine to run badly?

08-16-2005, 05:00 AM
runs terrible. msd is aware of the problem, im not the only one with the issue. but their only response is to drill holes in the cap to vent it. well i have a friggin vented cap. how much more vent do i need?

08-20-2005, 10:16 AM
May be its what the rotor arm tip or disi cap tips are made, they might have the tipsd out of cheaper metals were the old made in usa and the new ones in mexico or somewhere cheaper .

08-28-2005, 06:19 PM
I've had the same problems with my 85551 in my Nova. I disassembled my distributor, cleaned off the loose rust and sprayed "Rust Treatment" (made by Permatex, purchased at NAPA) on all of the components. I also replaced the cap at the same time and the new replacement cap came with a vent built in.
After reading your post, I went out and pulled the cap to take a quick look. There seems to be a small amount of rust coming back, but nothing like it was before. Not sure if the cap is helping, or if its the "Rust Treatment."

But I have to say, I'm very disappointed with my MSD Billet distributor because of this.....even though I haven't seen any drop in performance.

11-09-2005, 11:30 PM
I love MSD, but every damn distributor I have ever had from them ended up all rusty inside, even my brand new dist, is getting all rusty

David Pozzi
12-02-2005, 09:29 PM
Rust from the weights is common in GM distributors, and the MSD has that weight system. A very thin smear of vaseline or some dielectric paste for spark plug terminals should help, but don't load on so much that it splatters around in the cap. There's a lot plug terminals inside the cap and deposits on them are actually conductive and help reduce arc. Check the rotor tip and if all the firing is coming off one end of the tip, check your rotor phasing, it may be firing while it's not near the plug terminal.

If the trigger wires get reversed, your rotor phasing will be over 30 degrees off.

12-07-2005, 03:54 PM
rusty advance plates i can handle. my problem is green and crusty terminals.