Engine ate screw heads

[jpcode]

OK this is for my buddies infinity QX4 vs 3.5L 2002. It was running ok and then while idling it started making a lot of noise, seemed lit stuff was bouncing around in the intake and seemed to misfire but no smoke out the tailpipe. I started to take the motor apart and found once the top intake manifold came off that one of the flaps, I don't know what to call them either intake flaps or swirl flaps was broken off. The flap itself was actually in the intake pipe for another piston. Now what I am worried about is the screw heads that broke off that were holding flap in place obviously went through the motor. They aren't that big, what are my chances that they could make it out the exhaust valves?

[Buzzman]

Unfortunately, this is a known problem with these engines on the Pathfinder/QX4.
Those are the power valves, and the screws that hold them in come loose and get ingested into the engine.
The end result is usually a blown engine.
They are supposed to have loctite, but most don't.
A lot of the guys on this forum have taken the intake manifold off and tightened and loctited the screws as a preventative measure.
I did mine last year.
If the screws somehow made it through with minimal damage, then you may have saved the engine, but I doubt it.

There are a few threads on here on this subject.
There is a sticky at the top of this forum called threadlocker on power valve screws:
threadlocker-on-power-valve-screws-pics-t304263.html

[jpcode]

thanks a million for this I didn't they were called power valves

[4xq]

Misfire would probably be a bad sign. You could do a compression test on the cylinder that sucked the screws. Occasionally you get lucky and the screw gets spit out the exhaust valve, or embedded in the piston head. But you lost both, so odds are slim.

If compression is bad, you can go to car-part.com. Input your vehicle data, and select engine as the part. Used engines are available for under 400.00, depending on your area of the country.

[rgk]

There is a potential issue where no threadlocker was applied to the power valve screws during assembly; this is not a very widespread issue, however.
threadlocker-on-power-valve-screws-pics-t304263.html

They are supposed to have loctite, but most don't.

[jpcode]

OK, my screws did not come off, the heads broke off. What side of the flap is pressure being applied? What do these things do anyway?