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Anyone know how to fix a premature pop off valve?


Guest jjohart

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Guest jjohart

Hi, I've got an 83 ZXT with intercooler and boost control. According to my aftermarket boost gauge, the pop off valve is going off at 12.5. I bought it "modified" off of Ebay (prev. owner claimed it was set to pop off at 15).

Does anyone know someone who's willing to tighten this thing up, so it will pop up at higher boost (above15), or how hard it is to D.I.Y? It is a stock Datsun piece, which it appears to have lost its hi-hat-like cover, and it seems like there isn't much I can do with it, short of prying it apart!!

BONUS: IF I don't mind the risk, can I make my old, stock POV keep from popping if I drop epoxy inside the housing of it?

Thanks

John

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If it is the stock "pop of valve" then it's actually an Emergency Relief Valve or ERV. It should be located towards the back of the engine bay on top of the intake manifold. All this does is it releases boost pressure after a certain boost pressure. A real BOV goes b4 the throttle body. If this is the case then all you need to do is get a 1" compression plug from your local hardware store, remove the old ERV, and plug the hole with the plug. Then you need to go and buy a real BOV because your turbo does not like 12.5 psi reverberations. Hope this helps.

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Guest jjohart

No, I don't refer to blow off valve, which I already have (DSM gen 1), hooked up properly.

I am referring to the Pop off valve, located as the first reply said. This one appears to have been modified somehow, as it makes that crappy fssst sound when the pressure builds, at around 13.5pounds of boost-the stock unmodified one that came with my car starts fizzing at only 10.5 boost pounds.

So the question remains, since no one seems to know what the modifier did to increase the pressure needed to "pop" the POV (tighter spring tolerance), seems like no one has the answer to what I originally asked, as to how to incrementally increase its resistance, so I can at least get 15pounds boost. If nothing else, would I be best off just gluing up the inside of my stock POV, if I'm willing to rely soley on my boost control computer (Greddy Profec B) to regulate max boost?

Thanks again (waiting for more info)

John

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Looking down at your stock-modified pop-off valve, grab the internals with a pair of plyers and twist 1/8 to 1/4 turn and the internals will come out. Add a thicker or more washers between the spring and valve as needed to increase the spring pressure until the desired psi is achived.

The proper type of washers can be found at your local hardware store, they are often refered to as a fender washer.

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I posted a short paragraph on how to increase the pressure this safety valve will stand up to. All you have to do is push down the top and turn it to the left or right and it will come up and out, just don't drop the spring in. Now just get another smaller diameter spring to put in the middle of the stock one. You will have to experiment with different stiffnesses of springs probably. I'v had three 280zx turbo cars and I've done this to all of them when running slightly higher than stock boost. And also, you can't increase the spring pressure by adding washers, that will just reduce the amount of travel of the plunger. Just go to Lowe's or Home Depot and look in the spring section. There are some pretty soft springs that come two to a pack. They are a little long and will have to be trimmed to fit without binding. I'm sure someone will insert a useless smart ass reply to my solution now, but don't worry, it will work. :roll:

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If you really want to keep the pop off valve, I can vouch for what 2slo4u said. Thats pretty much what I did to mine and its really easy to do. Using washers can get you a bit more PSI before she pops if you really need it.

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