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Join Date: Jun 2014
Location: Cologne Germany
Posts: 197
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Air Box Pop Off Valve
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1994 968CS 1977 911S 1969 MGB GT 1958 Norton Dominator |
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Registered User
Join Date: Jun 2014
Location: Cologne Germany
Posts: 197
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Thought I would give my thread a bump, this time without the waffle.........
Airbox 'Pop-Off Valve', Opinions please. Cheers.
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1994 968CS 1977 911S 1969 MGB GT 1958 Norton Dominator |
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Join Date: Oct 2008
Location: Nash County, NC.
Posts: 6,978
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It’s an insurance item, if you were to have a backfire would the expense of the valve out weigh the cost of the air box and install on the engine?
Bruce |
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Join Date: Jun 2014
Location: Cologne Germany
Posts: 197
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Quote:
Cheers
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1994 968CS 1977 911S 1969 MGB GT 1958 Norton Dominator |
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POV vacuum test.........part I
Jason,
If you ever decide to install a POV on your car, don’t make the mistake of installing it without testing it. Some of these POV’s made by URO are defective or leaking not all but some. Regardless of brand name, test before installation to save you from some aggravation. There is a simple way to test to do it: ![]() ![]() ![]() Below is the picture of a brand new POV fresh from its packaging that does not seal. It failed the test and should never be sold. The POV (good) with yellow sticker is an old used POV and could still hold vacuum. ![]() This is about the POV itself. Installation is another story. The instruction sheet that cones with the new POV says to drill a 2” hole and glue it. This will work but not the best option for installing the POV. There is another option to improve the installation and promote stronger adhesion between the air box and POV. I will post the pictures later. My wife is calling me and it’s dinner time. Tony Last edited by boyt911sc; 02-02-2018 at 02:35 PM.. |
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Location: Cologne Germany
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Tony,
Thank you very much for the info and advice. You're right that the installation is one thing but the choice of bonding agent and method of curing it is a whole different kettle of fish. I look forward to seeing your recommendations about the installation. Hope you enjoyed your dinner? ![]() Cheers. Jason
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Revised POV installation.........
Jason,
Sorry for the delayed response. Been busy with the Engine Rebuilding Sessions preparation. I have attached some pictures regarding the revised POV installation procedure. Below are the conventional POV installation procedure: ![]() ![]() Below are the pictures of the Revised POV installation procedure: ![]() ![]() ![]() Aside from drilling the 2” hole for the conventional POV installation, trimming some small section of the ribs of the airbox allows the POV to sit lower and producing more surface contact area between airbox and POV. The extra surface contact area produces stronger and better adhesion. The shoulder or collar of the POV comes in contact with the airbox at the rib contacts and at a small circular ring using the conventional method. The contact area is minimal at best. So to obtain a stronger and better adhesion between the POV and the airbox, additional surface area is needed. I have been doing this installation for a long long time and been keeping it to myself. Time to share this experience with fellow CIS enthusiasts. For those people who have the time and interest into this trivial subject, measure and calculate the surface contact made by the conventional procedure versus the revised procedure. The difference is more than 4X. Finally, POV’s should be tested prior to installation. I have encountered several new from the box POV’s that we’re defective (not sealing). Whether you do the conventional installation or not, check the POV before installation. Tony |
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Location: Cologne Germany
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Hi Tony,
Many thanks for the great info and recommendations. I can see how this method would help to give a better bonding area and I will be doing the same thing on my airbox. Would you specify a high temp bonding epoxy? My POV didn't come with any and I am planning on using some Scotchweld DP 490 which is good up to 120 degrees C. Would you think this is enough? Cheers, Jason.
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Location: Cologne Germany
Posts: 197
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I drilled and prepared the airbox to Tony's specifications today and it's very obvious how much more of a bonding area will be available. Grinding down the fins on the airbox is pretty quick when using a Dremel.
This was done with the airbox off the engine so access to these areas is very easy. Attempting this with the airbox still fixed to the engine and in the car would be possible but it wouldn't be very comfortable, plus the grinding creates a lot of plastic swarf so keeping things clean would be a hassle. Cheers, Jason.
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