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White valve?

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Just pulled my head and noticed that one of the valves was white with flaking build up and had small scratches bellow the guide.

Previous owner claims he replaced all four valves 14hours ago (17-18h now) 

Any ideas what it can be? 

Been using alkylate fuel for 4-5 startups in the garage, but cant be that.

Going to rebuild the bottom end and put on a big bore kit. So want everything dialed and 100% fresh.

 

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Going on the info that: all four valves were replaced 14 hours ago.

The white valve is an exhaust valve. I am going to suggest that one valve was running quite hot. Either from being past due for clearance check and shimming or a leaking seat. There is evidence around it of a previous "dropped valve" failure. See the dings in the head around it? That would be the why and when all the valves were done. You've got a repaired/rebuilt head there.

So if that valve is hot, it will cook and burn carbon deposits hotter, which the white is an indication of. There is possibility that it is/was running over temperature, "white hot". All indications are you had better replace that valve, check the seat, and shim it properly. Metal properties change at high temperatures. That valve may now be a high risk of being soft, to either bend stem of snap off when you push it with that big bore power.

I hope you measured the clearances before pulling it apart so you have an "as found" baseline. What were the clearances? What are the numbers? Those would give us some data to base this on.

If you have money and are game to have "everything dialed and 100% fresh" to go with that new bottom and big bore, then considering a new head should be on your list. This previously refurbished head may, or may not, be a problem for future valve/seal failures. I suppose the decision on one valve or whole head depends on what your end game is as to how hard you are going to be running it.

 

 

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Yeah, going on all new steel valves and have the seats cut. Maybe a bad job on the valve guide? As you pointed out on the dings in the head, thats probably the one were the guide got replaced on.

Still think this head is in repairable condition thou?

The clearance specs were all god (on the lower side, I reshimmed it too ex .20 and in .15 to see if I hade valve knock)

 

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See the scratches on the valve? 

Might already be bent, so maybe I dodged a bullet with this BB kit.

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Heres a link to the tappning noise, any of you guys think these probs are related?

 

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