Direction of Air Box Pop Off Valve

[FL911SC]

I have a 1979 911SC with CIS. I am getting ready to install the recommended pop off valve in the air box.
My question is: does it matter which direction the valve is facing once it is installed? In the few photos I can find of the valve installed, it seems that opening is facing the front of the car (when the valve top is in the opened position). My thought is that spinning it 180 degrees and allowing the top to open toward the front of the car, putting the opening facing the rear, might be a better choice. My reasoning is that with the valve facing this direction, one could visually inspect the lower air box assembly. Inspect it for what? I don’t know. But it seems if I am going to drill a hole that big, I might as well be able to see what’s down there after a backfire episode.

So does it matter which way it is facing?

Thanks!

[Bob Kontak]

Check this thread out. See the last pic of my flapper open on my 81. Access is available to see if installed in this position. My 81 has more baffeling (sp?) than a 79 so you could probably see more than on mine.

CIS - Has anyone seen this before>

I wold not buck convention. If installed in the reverse, the flapper lid is real close to the bottom of the air cleaner element. I suppose it would work ok but if there is a big backfire and you need the flapper opening a lot (assuming this happens) you may find out the hard way that the added opening room is your friend.

[boyt911sc]

Originally Posted by FL911SC

I have a 1979 911SC with CIS. I am getting ready to install the recommended pop off valve in the air box.
My question is: does it matter which direction the valve is facing once it is installed? In the few photos I can find of the valve installed, it seems that opening is facing the front of the car (when the valve top is in the opened position). My thought is that spinning it 180 degrees and allowing the top to open toward the front of the car, putting the opening facing the rear, might be a better choice. My reasoning is that with the valve facing this direction, one could visually inspect the lower air box assembly. Inspect it for what? I don’t know. But it seems if I am going to drill a hole that big, I might as well be able to see what’s down there after a backfire episode.

So does it matter which way it is facing?

Thanks!

FL911SC,

Yes. If you decide to install the pop-off valve facing rearward, you'll regret later. There is a good reason why people installed it facing forward. There is nothing to inspect inside the air box after a big backfire. If there would be an inspection needed, you'll be inspecting the outside perimeter (seams) of the plastic air box. Just my two cents.

Tony

[ossiblue]

Absolutely turn the valve so the flap opens toward the front (hinge facing the rear of car)--I know!

The PO on one of my cars had installed the valve with the opening toward the rear, as you are considering. Any decent backfire would cause the flapper to lodge against the mesh of the air filter, keeping the flapper open. This happens because of the slope of the air filter.

Do yourself a favor, install it as shown with the opening toward the front of the car.

[FL911SC]

Seems like there is consensus on this one, so I will install it with the opening facing forward as recommended.
Thanks for the advice!!

I love this place!!!

[E Sully]

If mounted any other way the filter will stop it from opening properly.

[tazzieman]

Doesn't the valve come with a drilling template and clear instructions for installation? I think it does!