Gouge in titanium valve stem - is it toast?

[stownsen914]

I wound up disassembling my cylinder heads after I got them back from the shop and found a valve stem gouged. I assume tool marks. I should mention that the valves are titanium, which I understand may be more sensitive to stress risers from gouging. Is was a little tight coming out of the valve guide, but pulled out by hand.

Is this a problem?

[VFR750]

The valve stem seal may ride up that far under full lift. If it does it will likely get cut and start to leak.

The best you could do is remove all positive material and leave a trench.

I would imagine the deep groove for the split lock retainers is far more stressful than a linear gouge aligned with the stress vector.

As for the shop that did that....

[cgarr]

I would not use it, most likely put there when the top retainer was compressed to remove the keepers.

[stownsen914]

I disassembled the heads myself before taking them to the shop. These gouges weren't there upon disassembly - I would have noticed. Also, it appears that someone attempted to clean up / polish the gouges a bit, probably so they would pass through the guides.

There are three marks/gouges in the stem, they seem to be 120 degrees apart. Almost surely from a tool chuck?

[reclino]

Titanium is VERY sensitive to scratches becoming cracks. Working in the military aerospace industry, any damage like this would be cause for rejection.

[stownsen914]

I took another look at the valves this AM. I'm finding it hard to believe I gouged these removing the springs. I looked at the gouges using a magnifying glass, and they seem very defined, and don't show a leading or trailing edge I might expect if the spring retainer made the gouge. The gouges have sharper ends. I don't see any damage on the old or new spring retainers, or any metal shavings. But before I disassemble the rest of the heads I want to make sure I'm not damaging the valves myself. I'm using a generic folding clamp style valve spring compressor. I was compressing them using the lever action, but switched to using the screw handle to compress the spring (like a regular C clamp). Bad idea to use one of these?

[dannobee]

Valve chucks/grinding equipment use a tapered cone at that end to center up the stem. On the other end (closer to the head of the valve) they use some version of three rollers or balls to center up the valve. And even if they ground the tip, the machines still don't use anything that holds the valve using that small of a surface area.

But if they used a collet and lathe or mill, all bets are off.

No, I would not run it. And I'd inspect the other valves closely, too.

[stownsen914]

Thanks guys for the input - much appreciated.

So I'm trying to figure out whether my technique/tools in removing the valve springs could have caused the spring retainers to gouge the valve stems. I'm using a C clamp style spring compressor similar to the one below. I googled and couldn't find much in the way of pics of valve stem damage from improper removal. I'd expect a retainer to leave a gouge looking more like a semi-circle around the stem, not a linear gouge lengthwise like mine have. I always thought removing valve springs was a simple procedure - now I'm afraid to proceed!