So here's a weird problem. I have a valve that keeps getting too tight and tripping a missfire code. Specifically the rear intake valve on Cyl #3. I pull the valve cover and set it back to spec and everything is fine on the street until I do a track day and beat on the car a bit. Come home and magically it's misfiring again and that one valve is way too tight -so tight that not even my smallest feeler gauge fits.

No visible damage to the adjuster, the stem of the valve seems to be at the same height as the others. Clearance on the others remains within spec, and the head was rebuilt last year. Upgraded to AP2 retainers at the same time. Those also appear to be fine. Leak down on that cylinder is good (albeit after the valve is returned to it's correct spec). The clearance just gets tighter because it feels like it. Go figure, any thoughts?

 

Is the cylinder head all oem?

 

Does the locknut torque down properly - 14 ft lbs ? , just wondering if it could be stripped.

 

Yes it is. Rebuilt recently, but with all oem stuff.

 

Problem with the build.

The valve stem or seat is moving upwards. Bad guide, non-oem valve, seat not seated

 

I've seen this in BMW engines with bad or improperly fitted seats.