Valve stem wear opinion

[peabodyracin]

Recently I went to look at a worked set of 906 heads for sale. Some mild porting, larger valves, bronze guides, springs, etc and claimed to have less than 1000 miles on them. They did look to be low mile units and had been stored well.

Just about when I was going to reach for my wallet I noticed the tip of one valve had a slight "U' worn into the center of the tip. You could feel it with a finger nail and there was a bit of discoloration in the U area. Looking further I found another that had the same problem but also exhibited a second wear pattern about 40 degrees turned from the first pattern. Checking the other head I found yet a third one with the same problem developing, only less noticeable.

The seller seemed genuinely surprised when I pointed these areas out to him. He asked what I'd pay for them and I made an offer, considering I was going to have to disassemble them, possibly be replacing at least 3 valves and wondering about the valve guides. I've always been under the impression valves rotate somewhat as an engine is running. I wondered if a valve guide problem could interfere with this movement and cause this sort of wear. Anyway, my offer was not accepted and we parted ways on good terms. Nice guy and I don't think he was trying to pull anything.

I continue to wonder what was going on with these so thought I'd put it out here and see what your thoughts are. Thanks in advance!

 

[493 Mike]

Recently I went to look at a worked set of 906 heads for sale. Some mild porting, larger valves, bronze guides, springs, etc and claimed to have less than 1000 miles on them. They did look to be low mile units and had been stored well.

Just about when I was going to reach for my wallet I noticed the tip of one valve had a slight "U' worn into the center of the tip. You could feel it with a finger nail and there was a bit of discoloration in the U area. Looking further I found another that had the same problem but also exhibited a second wear pattern about 40 degrees turned from the first pattern. Checking the other head I found yet a third one with the same problem developing, only less noticeable.

The seller seemed genuinely surprised when I pointed these areas out to him. He asked what I'd pay for them and I made an offer, considering I was going to have to disassemble them, possibly be replacing at least 3 valves and wondering about the valve guides. I've always been under the impression valves rotate somewhat as an engine is running. I wondered if a valve guide problem could interfere with this movement and cause this sort of wear. Anyway, my offer was not accepted and we parted ways on good terms. Nice guy and I don't think he was trying to pull anything.

I continue to wonder what was going on with these so thought I'd put it out here and see what your thoughts are. Thanks in advance!

Heavy duty engines mostly, had rotators built into the retainers but, standard retainers do not rotate.
Mike

 

[peabodyracin]

Thanks Mike. I knew about rotators but for some reason thought the action of the coil springs induced a certain amount of valve rotation on most any valve in head arrangement. Too many years back to say where I got that opinion!

 

[DanielSlocum]

if guides are worn much.....the valve job will be on its way out. if the valves were ground once....might not have enough margin left if ground again.
the integrity of the whole thing really depends on the condition of the guides. not sure,but i suspect that all valves do rotate at least some.
bronze guides are said to last much longer than iron,and i think that is true. high spring pressure likely wears valve tips faster and also guides.