Odd 383 Distributer Cap (With Breather Hole)

[Mariposa Mike]

Recently replaced ignition parts on my 66 383HP Charger including the pictured black cap. Never seen one with a breather. Standard brand I believe. Anyone else seen these and have an explanation why it would be needed? Pertronix electric ignition if that matters.

 

[Vaanth]

Recently replaced ignition parts on my 66 383HP Charger including the pictured black cap. Never seen one with a breather. Standard brand I believe. Anyone else seen these and have an explanation why it would be needed? Pertronix electric ignition if that matters.

View attachment 1925381

The vent on the pictured cap is to relieve buildup of ionized gases, from the arcing of the rotor tip to the cap contacts, inside the distributor. The addition of the vent to replacement caps started in the 1980s.

 

[1 Wild R/T]

Breathers on distributor caps are common, they started appearing way back in the 70's as the energy delivered by ignition systems increased there was issues with high voltage causing ionization of the air trapped under the cap.... To be honest I don't understand the physics of it but here's a link...

Google Search

Basically the manufacturers were fighting ignition misfire issues and venting the cap solved it...

 

[1 Wild R/T]

The vent on the pictured cap is to relieve buildup of ionized gases, from the arcing of the rotor tip to the cap contacts, inside the distributor. The addition of the vent to replacement caps started in the 1980s.

So apparently my memory is fine & I didn't just pull all that outta my butt....

And I still remember seeing them first in 78-79 time frame..

 

[Mariposa Mike]

Holy Moly. I can create plasma in a distributer...and ions, atoms, electrons??? The 70's were different times. Maybe this theory came from some guy smoking something at the corner of Haight and Ashbury. Seriously though there must have some data that led to this. Maybe electronic ignition systems don't have this issue and they generally started in the mid to late 70's. Thanks for the explanation though. Like I say, never saw one before.

 

[DeltaV]

I always wanted a clear distributor cap.

 

[65CopCar]

My 95 Caravan had a OEM cap with the vent. Went a very long time. Subsequent caps had no vent and never made it past 10,000 miles. I learned to wash the ionized deposits off and dry them out in the oven. Got to the point I could immediately tell when it was time to change the cap and always had a spare with me.

 

[Mariposa Mike]

A clear cap would be very cool. Could stand there for hours and watch all 8 firing off over and over. Back in the day I never had an issue with a cap. Especially going only 10K miles. I did have issues once in awhile with the dual points. Recall one time going over Tioga Pass in Yosemite in my 67 440/375 HP Sport Fury. It began missing as I got to the upper altitude and ran fine after I dropped elevation. Turned out one set of points gap had closed down to about .010 and were slightly burned with a tit on them. Why that only showed up at altitude I don't know but adjusting them solved the problem until I could change them out.

 

[Ray70Chrg]

The vent on the pictured cap is to relieve buildup of ionized gases, from the arcing of the rotor tip to the cap contacts, inside the distributor. The addition of the vent to replacement caps started in the 1980s.

Mystery solved! I always wondered where those extra ions were coming from in my garage.

 

[1 Wild R/T]

A clear cap would be very cool. Could stand there for hours and watch all 8 firing off over and over. Back in the day I never had an issue with a cap. Especially going only 10K miles. I did have issues once in awhile with the dual points. Recall one time going over Tioga Pass in Yosemite in my 67 440/375 HP Sport Fury. It began missing as I got to the upper altitude and ran fine after I dropped elevation. Turned out one set of points gap had closed down to about .010 and were slightly burned with a tit on them. Why that only showed up at altitude I don't know but adjusting them solved the problem until I could change them out.

Probably due to the air fuel mixture getting so fat at altitude the weak spark couldn't fire certain particularly rich cylinders...

 

[1 Wild R/T]

Mystery solved! I always wondered where those extra ions were coming from in my garage.

See! The vented cap works!!!!

Thank God it was only extra Ions not extra Klingons!!!

 

[Ray70Chrg]

Truth be told, I thought it was a vent to release air pressure buildup when the engine was turning hi rpms.