twelve cylinder distributor caps why the holes ??

[M. Patla 13876]

for what reason would distributor caps have 2 small holes near the base? i have several 12 cyl caps and all have it. i also have a new 16 cylinder cap in the box and it actually has 8 holes at the base, all appear factory made. why? also, does anyone have a  SHURHIT CATALOG ? I would like to identify SHURHIT C-69  it could be early sixteen cylinder cadillac . thank you and happy motoring  M.PATLA13876

[Otto Skorzeny]

Could they be vent holes? Most distributor caps have some sort of vent hole or holes for moisture to escape.

[Mike GA]

I agree with Otto - vent holes.  A distributor can build up charged air inside the cap, leading to misfire.  I can't explain the science behind "charged air", but it has happened to me and drilling holes in an unvented cap will resolve it. 

I have heard of using epoxy to secure a fine mesh screen across the holes to prevent bugs and dirt from entering the holes.  Never tried that.

[mario]

if engine gets wet it also dispells moisture buildup in cap.
ciao,
mario

[Gergely Szentmartony 25603]

It is not only against moisture.
There is ozone generated inside distributor cap when rotor rotates and providing high voltage pulses to spark plug. This ozone is very very reactive in nature. Its always ready to combine with any other molecule.
Arie Jan Haagen-Smit and Conrad Vleck found that rubber exposed to high smog levels cracked in just seven minutes. Thus was born one of the early methods for measuring ozone levels - stretching rubber bands around jars and timing how long the bands took to snap.
So ozone generated by the sparks inside the distributor cap can "eat" the material of the cap.

[M. Patla 13876]

thank you for this information . now i have my answers thanks again  matt