Eric_P

My 79 SC has what looks like a factory pop off plug, held in loosely by the normal vacuum. Right side of airbox, about a 1" opening, barbed rubber plug. Can push it out easily, but seems airtight when running... anyone else have this? Definitely not aftermarket...
Am I off the hook for a "proper" pop off valve?

Off to John Walker's shop Tues for the tensioner upgrade and a valve adjust..

Peter Zimmermann

It's just a plug that was for a breather hose that's not necessary in your application. The plug prevents unfiltered air from entering the engine. It's not a pop-off valve, which is another story...
Pete

autobonrun

Peter, I have the same year car but I have a hose that goes from the hole mentioned over to the oil filler neck. Are you saying the 79SC doesn't need this hose or is there something specific to his application?

In addition, I think this is the hose that holds the backfire grid (flame arrestor). See a post I made earlier when mine was missing.

http://forums.pelicanparts.com/showt...=backfire+grid

Eric_P

autobonrun,
That's the part I'm referring to. I know it's not a proper pop off valve, but the slightest positive pressure should send it right out.
I'm gonna use it as a pop off for now...
Car runs great, so I assume nothing is missing/disconnected. Unless it's smog crap, in which case, I have a special box for that.

autobonrun

The pop off valve that is often referred to is installed inside the air box to vent off overpressure in the case of a backfire. The grid I linked to serves as a flame arrestor. Is the piece you're referring to the same as in my photo? If so, it will contain a mesh screen and the pressure drop is so low across it, there won't be enough to blow it out. It fits inside a hose. Is there a connection on the side of your oil filler neck? Looks like the last guy that posted has a plug in his similar to what you're describing. I'll wait to see what Peter makes of the differences between those with the plug and those with the hose/backfire grid.

psalt

Eric,

The plug you are looking at is neither a pop off cork or a flame arrestor, it is a remnant of CIS evolution. Porsche moved the oil tank breather after they realized it was plumbed into the wrong side of the air flow sensor. I am not sure of the production date change, but it may mean you have a replacement air box, if you are interested. It cannot function as a pop off anything because it is on the other side of the air flow sensor.

Paul