Drain Petcock Threading

[ruffy]

Does the (1977) Nova's drain petcock turn clockwise to open?

Don't want to start flushing my water until I know this.
My old caddy used to have the threading reversed, and
I figure, though don't know, all GM cars have it that
way. Would appreciate a confirmation or otherwise,
thanks.

 

[zora]

By turning it in, counterclockwise, you open the seat inside the petcock. There is a special tool/socket that grabs the ears of the petcock if you have trouble turning it.

 

[ruffy]

Thanks Zora; Funny they had to make it that way in the 1st place,
going against standard perception that clockwise "locks". Many a
newbie probably ruined petcocks on account of this "exception".

 

[zora]

double checked to make sure I explained it correctly here is what I found, should loosen counterclockwise

when tightening/loosening fasteners we always remember "Righty-Tighty, Lefty-Loosey" but with draincocks it's the opposite as it screws inwards to open the drain... turning it the other way could strip the "wing" handle of the petcock and then it's ruined... so you'd be tightening the wing handle so to speak...

To be clear, the petcock is normally reverse-threaded, therefore the "righty-tighty, lefty-loosey" still works. What happens is you turn the petcock to the left to loosen it/ let it drain, but in doing so, it actually goes "in" to the radiator.

 

[ruffy]

Zora, you wrote "you turn the petcock to the left to ... let it drain".
You probably meant the opposite, didn't you?

Have I got this straight:
By turning the petcock CLOCKWISE, I drain the radiator,
because the petcock opens up as it travels INTO the radiator.

That means the threading quite normal, it's just that we happen
to actuate a drainage thereby, because of the internal mechanics.

Whereas to close the drainage, we turn COUNTERCLOCKWISE,
because "unscrewing" the petcock in effect stops the drainage.

But the THREADING, therefore, is quite NORMAL, where clockwise
screws inward and vice versa.

 

[zora]

my reading of it is the opposite, to drain the radiator turn it counterclockwise because it is reverse threaded and will cause the handle to go inward, didnt you state your Cadillac was the same? Sorry about the confusion.

 

[ruffy]

There are few non-automotive occasions where reverse-threading is the rule.
The single one I know of that's automotive-related is the petcock - at least
it WAS for my old caddy. But now Zora you confirm it's the same for the
Nova.

I was going to say the inward-outward thing is confusing, and practically speaking, irrelevant. But where it may be relevant is that as you turn the
petcock to flush the radiator, it may help you to simultaneously press inwards
to help it along.

Anyhow, I am not going to take a chance with the petcock. I am going to
unfasten the lower radiator hose instead. Thanks Zora.