If there is positive pressure inside the cooling shroud, wouldn't these seal better if they where pushed inside the cooling shroud? I've always installed them on the outside. Do you?

The bigger "flange" for lack of a better word should be on the outside with the smaller one inside. You are probably right that it would seal better the other way around, but the way the rubber bits get mis-shapen, it probably doesn't matter anyway.

Konrad

Hey, that's a good idea.

I always put the bigger flap on the inside. I just thought it was supposed to go that way.

The #2 cylinder does not quite seal, but all the other seal way better then with the flap on the out side (the #2 seals better too, just not perfectly.)

My plug wires only have the one big flap, not a smaller inside flap. My earlier set of wires did not have the smaller flap either...

Zach

I was going to make some fiberglass covers that fit the sheetmetal real tight and have a hole for the wire to thread thru. They'd be held in place by a sheetmetal screw.

It's on my bucket list....

JMHO, but maybe that seal has another purpose? Maybe to keep things out? Water? But if it is just for an air seal; I gotta agree w/ you Elliott.
Sealing w/ pressure rather than against pressure makes sense.

...Until they get brittle from the heat and then break off inside the shroud the next time you pull a plug wire...

You can put them inside if you like - I am not the spark plug air seal police. Since T-IV sheet metal is curved in that area a good seal is problematic anyway.

"Supposedly" you can slide them up and down on the connector a bit to improve their loading against the shroud. Probably you'll find they're already too brittle for this.

Some of the plug makers (Magnecore comes to mind) have nice seals of heat-resistant rubber with the small inner flange and a large outer flange designed to snap into the hole and stay there. I haven't tried them on a T-IV so I can't say they're actually better in this regard.

Another use for duck tape? Hee, heee. Just kidding. My new wires came with nice ones and seem to seal just fine. Had them off yesterday checking the plugs. That anti- seize I used 2 years ago sure worked well, plugs came out easy as pie.
Tom