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?

[Krieger]

Do you ever check to see if the rocker arm hold down bolts are tight? I had a car that those studs slowly pulled out... Out of habit I check every time I do the valves on my 4 cylinder.

[ClayPerrine]

It sounds to me like you are starting to lose a valve seat.

Clay

[914werke]

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[Superhawk996]

(IMG:style_emoticons/default/agree.gif)

Valve seat is probably moving into toward the combustion chamber and pulling the valve stem away from the rockers and adjusters, increasing the clearance.

Better to tear it down now than wait.

You may have something making cylinder #1 run too hot. Again better to find out now than keep waiting for something catastrophic.

[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]

Do you ever check to see if the rocker arm hold down bolts are tight? I had a car that those studs slowly pulled out... Out of habit I check every time I do the valves on my 4 cylinder.

I tried to wiggle things and it was all tight, but I’ll look at the rocker studs closely the next time I’m in there. I think if the rocker stud was going it would affect the intake to some degree and that is maintaining a perfect 0.006 adjustment.

[KSCarrera]

The other thing to consider is that the pushrod is eating into the cam follower – not at all an unknown problem. As soon as the hardening starts to wear, it will keep eating and eating, meaning the clearances will keep opening up. Pull the pushrod out and check the tip at the inner end. Then remove the pushrod tube and withdraw the cam follower so you can take a look at the seating surface where the pushrod sits. A simple check to carry out before you get into pulling heads off. At least that's one check you can do on a Type 4-based engine you can't do with a VW Type 1!

[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.

Is anyone rebuilding 914 heads at this point? I didn't realize Len was no longer rebuilding used 914 heads - I've been away for too long.

Are the LN-200 heads the ones you are referring to? I looked at the price on the LN site.. I don't think it makes sense to invest in new heads on this motor. There's enough other issues with the motor and the car. I'm just trying to get the car driveable for a while until I am ready to restore it.
I do have a bunch of engine parts set aside, maybe enough to build a 2nd motor so I could swap it for this one.

[yeahmag]

I’d think loosing a cam lobe to be the most likely. Pull the pushrod and use a magnet on a stick to pull the lifter and inspect.

[Superhawk996]

Also take a close look at that spring retainer. Can't tell if that is some sort of casting / stamping flash or if you have cracking starting on the circumference of the retainer where it transitions into the keeper pocket. May just be the lighting of the photo but take a close look.

[mightyohm]

I’d think loosing a cam lobe to be the most likely. Pull the pushrod and use a magnet on a stick to pull the lifter and inspect.

Cam lobes are shared so it would not affect just one cylinder...

[mightyohm]

Also take a close look at that spring retainer. Can't tell if that is some sort of casting / stamping flash or if you have cracking starting on the circumference of the retainer where it transitions into the keeper pocket. May just be the lighting of the photo but take a close look.

Yeah, that does look weird. I'll have to take a closer look.

[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.

[Superhawk996]

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.

Not great. Best course of action is a new head.

Once a seat loosens from over heating the vibration, hammering action of the valve on the seat tends to enlarge the valve seat pocket, loosing the shrink fit it was intended to have.

I've repaired loosend seats in lawmowers by peening the valve seat in place but this is noting but a crude field fix. Not worth the risk in my opinion.

To repair it properly would involve welding the seat pocket and then remaching it for a proper shrink fit. The cost of doing that properly is not much less than a new head and then you know it's proper.

HAM has great options and is reaonable pricing on new heads when you consider all the labor and parts involved to do it properly.

I personally would not replace just the head without looking to find out if you're overheating that cylinder.

Of course if you find that retainer is cracked, just replace the reatiner and see where you're at.

[Montreal914]

You can contact Jorge at European Motorwerks in Hawthorne,CA. He repaired my 2.0 heads. Depending on cost of new head, yes you might be better off getting new ones. Worth the call to see once you have the head in your hand.

If you say the engine is probably not worthy of getting new expensive heads, then your choice is fixing it without too much of an investment (repair) and cross your fingers or get new heads and fully rebuild your engine while taking that opportunity to bump it up to 2056. (IMG:style_emoticons/default/driving.gif)

Then, there is also the option of finding a good running engine, dismantling this one and see what could be saved for a future build, or sell the parts to help pay for the used engine.

Good look! (IMG:style_emoticons/default/beerchug.gif)

[djway]

A friend had a similar situation on a T1 rebuild. When he opened the motor back up the tappets had ground away to nothing.

[Bleyseng]

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.
The local shop I know for VW/Porsche aircooled heads sucks so don't bother.

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.