WTF Pop Off

[Bicykiller]

Sooooo engine starts running poorly and I immediately suspect a vacuum leak because the pop off valve looks like this from the PO...
Not only is it installed wrong, but it looks TERRIBLE! It's leaking pretty badly. What's the easiest way to remove the epoxy surrounding it cleanly so I can reinstall the proper direction AND neatly!

[patkeefe]

It is ugly. What makes you think it is installed incorrectly? Does it leak (well, where is it leaking...at the epoxy or the actual rubber seal)?

[Bicykiller]

It opens perpendicular to the front/back of the car (the hinge is on the passenger side), from everything I've seen they are meant to open with the hinge to the rear?? probably not the biggest deal, but yeah, it's fugly.

It does leak bad at the base, not the seal, you can hear the air sucking through and when I put my fingers around it, it sounds like when you put your hand over a vacuum cleaner hose.

[patkeefe]

Try some of this stuff from Amazon over the epoxy and see if it stops leaking.
I think it's Seal All. It is one of the few things I have found that actually sticks to the PPS airbox.

I don't think the orientation matters in the install. The quality of install does matter.

[Bicykiller]

Originally Posted by patkeefe

Try some of this stuff from Amazon over the epoxy and see if it stops leaking.
I think it's Seal All. It is one of the few things I have found that actually sticks to the PPS airbox.

I don't think the orientation matters in the install. The quality of install does matter.

Great, will order it.

Any tips for removing the pop off and current slew of epoxy?

[Mark Salvetti]

I'm pretty sure you want the hinge towards the rear, so the valve opens facing the front. This way it's less likely to get hung up on the air filter if it ever pops open.

Mark

[2jmotorsports]

You going to remove the pop off and epoxy with the airbox still in the car? That sounds super risky as you may have bits of epoxy and other debris getting down into the intake runners.

If you have it out of the car, some chemical strippers are effective at removing epoxy. I used Jasco to strip the old epoxy off my engine case plugs before cleaning up and reapplying new epoxy.

[smadsen]

Go for a long drive in the desert. It will always fall out at the most inopportune time.

Then go to a plumbing store an get about a 1-1/2" expansion plug and plug the hole in the air box. Air tight $5.00 fix.

I'm kind of a linear guy, but on this one I'd plan ahead and get the plug before you venture into the desert alone.

The two-stage epoxy doesn't stick to whatever the air box is made out of very well.

[patkeefe]

The epoxy probably didn't stick to the airbox, so you can likely scrape it off pretty easily. The airbox is made from Ryton, a form of polyphenylene sulfide. Few things will adhere to it properly. Loctite makes a product, but I don't recall the name of it offhand.

Stuff could fall into the airbox, so vacuum it out real good when you're done (do you have the cold start spider?) Be careful

If you have a backfire, it only opens a small amount, enough to relieve the pressure wave. So, it may or may not interfere with the air filter. Was the car running OK, and then suddenly started running poorly? Did you have any backfire events prior to it running poorly? Is there any evidence of it contacting the air filter now?

I would also suggest you drop a PM to boyt911sc, who has a ton of K-Jetronic experience and expertise in these matters.

[Flojo]

Originally Posted by patkeefe

It is ugly. What makes you think it is installed incorrectly?

the hinge has to face to the rear of car.
should be turned clockwise another 90 degrees to the right.
so when it pops, it's lid alignes with the airfilter

[boyt911sc]

Originally Posted by Mark Salvetti

I'm pretty sure you want the hinge towards the rear, so the valve opens facing the front. This way it's less likely to get hung up on the air filter if it ever pops open.

Mark

Mark,

You are indeed correct. The POV could be installed in several orientations but the right one is the hinge towards the rear bumper. A heat gun is the tool to use to remove a POV with epoxy resin.

Tony

[JSZ]

The other thing you may want to consider is to scribe the outline of the pop valve on the ribs, with it in the correct orientation and then carefully remove the ribs, utilizing a dremel. Why I propose this, if you look at the side view of the pop off valve, near the base of the hinge, there is a very nice flange to allow more surface area for the adhesive joint. If you do not scribe the ribs, you get a small adhered surface area the thickness of the air box wall, something to the tune of .0100" if I remember correctly. And in a perfect world most of the adhesive is pushed away from the joint during install, providing a joint where the vacuum qualities are suspect. I also utilized in my second install of the pop valve, a 3M plastic epoxy for the automotive industry. Forget the JB weld. Also a nice burr on the dremel is great for removing old epoxy and preparing the new surface for proper adhesion of the epoxy.

I can see if I can get a couple of picture of the pop valve. Currently my complete CIS system is packed away as I am going to a PMO ITB setup

[boyt911sc]

Some pictures for those planning to install POV correctly......








Test the POV before installation. Some of the new POV’s are defective right from the box. Do not install the POV unless it passed a vacuum test for leak. If you don’t trim the fins or ribs, the POV will be sitting high and less contact surface between the air box and POV.

Tony

[Marc Bixen]

DO NOT CUT THE RIBS! REPEAT DO NOT CUT THE RIBS!
Inside the late airbox is a cold start distribution rail (silver spider looking item). If you cut the reinforcing ribs, the pop off valve will bottom out on the distribution rail and render the pop off valve relatively USELESS.

[boyt911sc]

Originally Posted by Marc Bixen

DO NOT CUT THE RIBS! REPEAT DO NOT CUT THE RIBS!
Inside the late airbox is a cold start distribution rail (silver spider looking item). If you cut the reinforcing ribs, the pop off valve will bottom out on the distribution rail and render the pop off valve relatively USELESS.

Marc,

I hate to disagree with you. And I hope you don’t take this personally. This is a technical forum and we could argue and disagree all day long. And at the end of the day, no hard feeling towards one another. Let’s discuss this with the intention of finding the facts. I will present data, measurements, etc. for discussion. Let the public decide.

I will be back........

Tony

[wgirardot]

Subscribed, and eagerly awaiting data to verify if mine is installed correctly

Bill

[pmax]

Originally Posted by smadsen

Go for a long drive in the desert. It will always fall out at the most inopportune time.

Then go to a plumbing store an get about a 1-1/2" expansion plug and plug the hole in the air box. Air tight $5.00 fix.

Not a bad idea.
Plug the hole up and fix the system.

I'm kind of a linear guy, but on this one I'd plan ahead and get the plug before you venture into the desert alone.

The two-stage epoxy doesn't stick to whatever the air box is made out of very well.

In addition, hard epoxy on a plastic deformable flexible box will not work. How did that practice become commonplace in the world of CIS "upgrades" ?

[gregpark]

I'd use a super sharp small chisel with a vacuum running at the business end and try to remove just the adhesive.
To reglue mine I used PL urethane construction adhesive years ago and the bond is like a weld.

[Marc Bixen]

Boyt911,
Another reason that I restrain from answering questions here. In the 80's I worked for the company that developed, held the patent for, and manufactured the pop off valve. Trust me, what I tell you is true. The efficiency of the pop off valve is GREATLY reduced if you cut the ribs. I assume if you want to trim the skirt, you may, MAY , reintroduce some of the original design efficiency, but all dimensions of the valve were made and tested for mounting on top of the ribs. I wont get in a spitting match, these are the engineering facts of the pop off valves intended design. You can get all the "opinions" you want. I was there!

[boyt911sc]

Originally Posted by Marc Bixen

DO NOT CUT THE RIBS! REPEAT DO NOT CUT THE RIBS!
Inside the late airbox is a cold start distribution rail (silver spider looking item). If you cut the reinforcing ribs, the pop off valve will bottom out on the distribution rail and render the pop off valve relatively USELESS.

Marc,

I don’t know where you got the idea that mounting a POV with the fins/ribs trimmed will bottom out and come in contact with the spider rendering the POV useless. The data and measurements I will present will show that you are incorrect. The POV will never come in contact with the “spider” using the revised installation procedure.

EVIDENCE #1:




The distance between flat top of the “spider” and the bottom fins/ribs is between 15~16 mm. Measurements taken from several samples (airboxes with plumbing).

EVIDENCE #2:
Picture of a POV installed with fins/ribs trimmed. The pictures below show the interior ribbed section above the “spider”. The POV will protrude below the inner ribs between 3~4 mm. And will not come in contact with the “spider” as claimed by Marc B. The height of the ribs/fins is 10 mm.




EVIDENCE #3:
The POV is designed to be mounted so that the collar or shoulder comes in contact with airbox for more surface area.


For someone to claim that a POV installed with the fins/ribs trimmed will bottom up and rendered useless is TOTALLY NOT TRUE. There is approximately 1/2” clearance between the spider and the bottom of the POV (revised installation).

So where did the idea of the POV coming in contact with the spider is a MYTH. I rest my case.

Tony