Questions about Popping Off Valves!

[Captoz]

Just getting ready to install a pop off valve in my 911. Have read Wayne's directions in the book and on line, just a bit nervous about cutting into my airbox.
Any tips or mistakes to watch out for?
Also I am interested in the fact the door opens into the airbox. Is this to allow air in to equalize the pressure after an explosion? Silly me though it should have been the other way around.

Cheers
James

[Bob Kontak]

I have a flapper that pops outwards - hmmm. I will look at Wayne's book now but I think you are mistaken.

[Bob Kontak]

The door opens up - away from the inside of the airbox. However, I am not walking in your shoes. What does your hardware look like?

[tazzieman]

Originally Posted by Captoz

Just getting ready to install a pop off valve in my 911. Have read Wayne's directions in the book and on line, just a bit nervous about cutting into my airbox.
Any tips or mistakes to watch out for?

Measure twice , cut once!
The main thing is to drill a small pilot hole before using the hole saw. Also , be careful not to drill into the metal of the manifold. This won't be an issue if you use the short bit that comes with the hole saw. You dont want a hole in the metal , nor metal chips! Some plastic shavings are to be expected and no drama if you can't suck them all out.

I was careful to sand/fine file off all edges and obtain a snug dry fit before epoxying with temperature resistant glue. The valve works like a champ! These cars often give a little cough at startup , even when tuned.

[Captoz]

The valve I have from our sponsor opens into the inside of the air box. Just like what is shown in the book and the on-line notes.

My wrapped mind just thought it would open out wards to allow over pressure to escape in the course of an explosion.

Thats why I thought I would ask in this group before I glue it in.

I am a beginner at this stuff and don't always see the reasons behind things because of my lack of experience, thats why it's great to be able to ask this group when you are in doubt.

Cheers
James

Originally Posted by Bob Kontak

The door opens up - away from the inside of the air box. However, I am not walking in your shoes. What does your hardware look like?

[Bob Kontak]

If you are looking at page 97 - bottom of three pictures - it opens up. I am going to go right now and get pictures and then you can feel small. :-)

[Captoz]

Feeling small is a small price to pay.

Cheers
J

Originally Posted by Bob Kontak

If you are looking at page 97 - bottom of three pictures - it opens up. I am going to go right now and get pictures and then you can feel small. :-)

[wwest]

The pop-off valve can be eliminated with the new intake "manifold" that incorporates the internal fuel distributor that prevents the fuel from pooling.

[Captoz]

I am coming up for a CIS rebuild, sounds interesting, can you piont me towards a URL on the product.

Cheers
James

Originally Posted by wwest

The pop-off valve can be eliminated with the new intake "manifold" that incorporates the internal fuel distributor that prevents the fuel from pooling.

[Bob Kontak]

Sorry - had to stop off in the kitchen and get some ice cream with Hershey's chocolate syrup.

Hope this helps. Again, this is what I see.

[Captoz]

Thanks Bob, thats the way I am putting mine in.

I was was just stuck on the idea that to relieve a backfire in the system it should have opened the other way.

Shows what I know!

OK out with the hole saw and the glue. Thanks mate!

Cheers
James

Originally Posted by Bob Kontak

Sorry - had to stop off in the kitchen and get some ice cream with Hershey's chocolate syrup.

Hope this helps. Again, this is what I see.

[Bob Kontak]

I bet Vegamite is better than this ice cream. Maybe not.

[Howard M]

Two suggestions: Use a small dental mirror to check your cementing technique BEHIND the valve. There should be a generous fillet of cement all around the joint. Remember, any air creeping through the joint is an uncompensated CIS leak. Also, carry an appropriate size expandable rubber plug in the glove compartment, available at any parts store. If your valve pops out of the hole due to a cement failure the plug will get you back on the road until a proper fix can be made.

[E Sully]

The valve must face in to work. If it faced the other way, it would hit the air filter element and not open.

[ossiblue]

Originally Posted by E Sully

The valve must face in to work. If it faced the other way, it would hit the air filter element and not open.

True, it must face inward as shown in the picture. Facing outward, the flap will pop up, but the clearance between the flap and the sloping air filter element will likely cause it to be wedged in the open position--massive air leak with the resulting failure-to-run consequence.