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Jase77's Avatar
 
Join Date: Jun 2014
Location: Cologne Germany
Posts: 165
Air Box Pop Off Valve

Hi Fellas,

I am nearing the end (hopefully) of my engine rebuild and I would like to hear your opinions on the Pop Off Valve for the airbox. I have to replace my old air box as it had a badly repaired crack in it.

I have the new airbox and it has a kind of diffuser feature in it which I believe was a factory update from around 1980. From what I have read this is just another reason why a Pop Off Valve shouldn't be needed.

My old air box had a valve fitted and the engine never back fired in 3 years of ownership, so I guess that the C.I.S was calibrated fairly well?

I have read recently that if your C.I.S motor is running correctly then it shouldn't need a Pop Off Valve fitted at all. There are also lots of stories about valves failing etc.

So, should I fit a new valve into my new airbox for added piece of mind, or should I concentrate on setting up my C.I.S properly and keeping the valve on the bench?

This will all be fitted onto a freshly rebuilt 1977 2.7. To say that I am crapping it about that first start up procedure is an understatement and I would rather not have to be worried about the airbox being blown to pieces as well.

As always, your comments, opinions and advice is always welcome.
Cheers,
Jason.
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1977 911S
1969 MGB GT
1958 Norton Dominator
Old 11-06-2017, 12:47 AM
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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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1977 911S
1969 MGB GT
1958 Norton Dominator
Old 11-16-2017, 11:44 PM
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Location: Nash County, NC. Just west of Rt 95
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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
Old 11-17-2017, 03:32 AM
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Quote:
Originally Posted by Flat6pac View Post
Itís 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
Fair point Bruce.
Cheers
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1977 911S
1969 MGB GT
1958 Norton Dominator
Old 11-17-2017, 04:13 AM
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Join Date: Mar 2002
Location: Philadelphia, PA
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Garage
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 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; 11-17-2017 at 07:18 PM..
Old 11-17-2017, 04:22 PM
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Join Date: Jun 2014
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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1977 911S
1969 MGB GT
1958 Norton Dominator
Old 11-17-2017, 10:52 PM
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