exhaust valve clearance keeps increasing Options

[mightyohm]

Hey all,

Long time, no posts.

I am having a hard time keeping the valves adjusted on my 914. I stopped driving the car a few years ago due to this issue, but have started working on it again. The clearance on #1 exhaust keeps increasing rapidly between adjustments. (The valve is getting looser and louder.) After a few hundred miles, the valve is making an awful racket. I just checked clearance today, and after about 1000 miles I had several times the specified 0.008" clearance (it could easily have been 0.050" or more - too big to measure). I adjusted the valve and I am running out of adjuster screw! See the attached pic. The other valves are fine.

Any idea what's going on here?

I pulled out the adjuster and it looks relatively fine - some flat spots from running with extreme clearance but it's not like the end is worn off.

I pulled the pushrod years ago and it seemed ok. But I should probably pull it again.

The car has solid lifters (I believe they are ceramic, installed years ago).

I would think that if I was dropping a valve seat, the valve would be tightening up vs. getting loose. But that could be what is going on. The car runs fine once I adjust the valve.

I would think that if the cam is losing a lobe, it would affect two opposed cylinders. Only #1 has this problem.

Any other ideas before I tear it apart?

[Bleyseng]

Order brand new heads from Len @ HAM now as your exhaust valve is recessing into the head. The chances are the seat will come loose and then you will spend the big bucks rebuilding the engine.

[mightyohm]

Order brand new heads from Len @ HAM now as your exhaust valve is recessing into the head. The chances are the seat will come loose and then you will spend the big bucks rebuilding the engine.

If the seat was recessing into the head, wouldn’t the valve be getting tighter and not looser? That would move the valve stem towards the adjuster, not away.

I’m not saying that it’s not a valve seat issue, but I’ve had a seat fail before (another car)
and as the valve sunk into the head it caused the exhaust valve clearance to tighten up.

Thanks to everyone who replied - the consensus is that it’s a valve seat problem of some sort. That was my gut feeling as well and why I stopped driving the car years ago. I was hoping that maybe I had overlooked another possibility and that it might be a simple fix, but I think it’s time to start planning a tear down.

[Superhawk996]

Order brand new heads from Len @ HAM now as your exhaust valve is recessing into the head. The chances are the seat will come loose and then you will spend the big bucks rebuilding the engine.

If the seat was recessing into the head, wouldn’t the valve be getting tighter and not looser? That would move the valve stem towards the adjuster, not away.

I’m not saying that it’s not a valve seat issue, but I’ve had a seat fail before (another car)
and as the valve sunk into the head it caused the exhaust valve clearance to tighten up.

If you're gaining clearance seat is not recessing into the head.

A dropped seat occurs when the head gets too hot and the shrink fit that holds the seat into the head loosens. The seat then falls out of the head typically jambing under the open valve and then damaging the valve, head, and piston when parts collide.

In your case, you may have a seat that has moved part way out of the head but then cools off and the seat is no longer fully seated where it should be. This pulls the valve stem away from the rocker and increases clearnace.

Regardless of what the cause is, you need to disassemble and figure it out before you have a catastropic failure.

[mightyohm]

If you're gaining clearance seat is not recessing into the head.

A dropped seat occurs when the head gets too hot and the shrink fit that holds the seat into the head loosens. The seat then falls out of the head typically jambing under the open valve and then damaging the valve, head, and piston when parts collide.

In your case, you may have a seat that has moved part way out of the head but then cools off and the seat is no longer fully seated where it should be. This pulls the valve stem away from the rocker and increases clearnace.

Regardless of what the cause is, you need to disassemble and figure it out before you have a catastropic failure.

That all makes sense. Thanks for confirming my fears. This is why I stopped driving the car years ago. I tend to be overly cautious so I was hoping that I had overreacted, but I guess not.

What are the chances a failed seat could be repaired? I've had seats repaired on water cooled motors but not the 914. Could I take the head to a local shop or is it not worth the risk? I remember years ago the talk was that most engine machine shops were not qualified to work on 914 heads.