What's this hole in the distributor for?

[714Speed]

My 71 350 came with a new Mallory unit distributor and I was wondering if anyone knows what this hole is for. It is a small hole on the front of the distributor, at the same height as the tachometer cable fitting. When I bought the car someone had put a little piece of duct tape over it. I assume to keep dirt out of it. Anyone know what this is for?

[Yoda]

Not sure, but you might be refering to the Dwell Adjustment Window. Is there a small metal flap that you move up to open, or down to close the window?

Bud

[714Speed]

No, no flap, just a simple small hole. I suppose I should keep tape over it until I figure out what it is, but your suggestion makes sense. Thanks.

[luvmy73]

Does it look like someone cut the hole out, or was is fabricated with the cap?

[Jack]

Originally posted by 714Speed
My 71 350 came with a new Mallory unit distributor and I was wondering if anyone knows what this hole is for. It is a small hole on the front of the distributor, at the same height as the tachometer cable fitting. When I bought the car someone had put a little piece of duct tape over it. I assume to keep dirt out of it. Anyone know what this is for?

Either no pic or I don't have pics enabled ... BUT ... it sounds like you may be describing the hole where a threaded Zerk grease fitting screws into ... like what you see on tie rod ends & ball joints ... that'd be my guess.
JACK

That was my first thought....some kind of lube fitting

[Twin_Turbo]

This one here (also duct tape on it) ??

[vette-dude]

I had one of these dist. on a former race car and it seems to me that this hole was to set up your advanced weights with a little plastic tool that came with the dist. This allowed you to dial in when you wanted the mechanical full advance to come in. At least I think that was what it was for. CRS has cause my memory to fail at the most inopportune times.

Randy

[Twin_Turbo]

yes, there's a "key" to set that.

[714Speed]

Twinnie: That's exactly what my distributor looks like. So, should I leave the tape on there to keep out dirt, or is it okay to leave it open? I doubt Mallory intended for "tape" to be one of their hardware parts..........Many thanks!

Neil

[Twin_Turbo]

I have tape on mine. I think there was probably a rubber plug that would go in there but I don't have it either. I'd leave the tape on there.

[vettepilot]

Originally Posted by Twin_Turbo

I have tape on mine. I think there was probably a rubber plug that would go in there but I don't have it either. I'd leave the tape on there.

Is the inside of the hole threaded, or is it smooth? If it's threaded, I would install a small machine screw to seal it. If not threaded, then I would tap it and then install a screw. Making certain it doesn't bottom out on anything inside of course.

vettepilot

[Twin_Turbo]

It's smooth, still running with the tape but I will probably pull the thing apart and tap it for an o ring boss plug or something.

[norvalwilhelm]

I had to drill my cap full of holes to allow air to circulate. Air trapped in the small cap was being ionized I think the word is but it is caused by the high voltage in a small area. Anyway the air was ionizing causing the spark to jump to other cylinders. The fix for this is holes in the cap to allow air to circulate inside the cap removing the ionized air.
I have run this way for 12 plus years without a problem. Still on the original cap and rotor.
I would forget the hole, leave it open and let the air circulate.

Originally Posted by Twin_Turbo

It's smooth, still running with the tape but I will probably pull the thing apart and tap it for an o ring boss plug or something.

[Twin_Turbo]

yeah, ozone is a problem, I have 2 little holes in all my caps too jsut to allow for circulation. Full of holes? WOW

The hole for the key is quite big and it can allow dirt into the cap, it's just way too large.