Valve/guide seizure

If you do a lot of guides (C630 or AMPCO45), or you just want the best tool with money no object, this system just might be the way to size them. Kibblewhite recommends diamond hones and plenty of coolant.
https://goodson.com/blogs/goodson-gazette/black-diamond-valve-guide-honing-system
C630 and similar bronze alloys are really tough on reamers, and there's a risk of snapping one off in the guide. I use a very similar hone to this Goodson unit for my guides, with an assortment of stones for different internal finishes, it works great on Triumph tappet guide blocks too

 
Is it possible that the valve seized in the full open position leaving compressed springs and slack rocker ? That may explain collision-
I don't believe that a valve in full open can touch the piston - at least that's the impression I got watching the valves with a borescope in a Combat engine. Interfering with each other, that's a different issue. I recently wrote about a 750 with the pistons in backwards. The intake did just barely touch the piston flat area.
 
This

Also not sure what guide material was used, KW sells different types. If C630 they need special equipment to size correctly
Yes , KW warns against carbide and high speed reamers with C630
 
If the intake valve got tangled on the exhaust valve, it could delay it's closing long enough for the piston to arrive and hit it.
Yes, this what happened. If I could I would insert a photo of the piston top
 
Educate me. Is this C630 bronze alloy so hard that reamers won't work? Back in the day, I did all the head work in our shop and I used hand reamers on both cast iron guides and phosphor bronze (I think that what I remember they were made of). The boss did the race engines and had cautioned me about tight guides. This was and is not as desirable as tightness in particularly body parts elsewhere. I never had a comeback for a seizure or excessive oil consumption.

However, on my pickup engine I had a head specialist do the head with hard seats, phosphor bronze guides, stainless valves and Perfect Circle seals. I trusted his work and just put the head on the engine and went on down the road. A few weeks later I did have an exhaust valve seizure after 100 miles on the freeway. It released by itself after a few minutes of cool down. I subsequently richened the main jets (adjustable) an eighth of a turn and advanced the spark a couple of degrees. Forty thousand miles later I had that head off and checked a couple of exhaust guides at random. No stem wear and no guide wear according to my bore gauge. They make a nice pop sound when you pull them out with your thumb over the end of the guide. This was just as I would have expected had I newly set up a Norton head in the past.
Well you were more lucky than me. The valve job was done by a specialised shop, so after a walk seeing tools and numerous engines being repaired, I trusted them. I'm just a rider and must rely on them. I guess they know what to do or would have closed if not reliable
 
Reading your posts, the consensus is .0015'' intake and .0020 ''exhaust. The problem is that I took KW specs, .0008''-.0012''intake and .0012''-.0015'' exhaust. I can't tell what figures the shop achieved, but even if they used the upper scale, it is too tight. Am I right?:rolleyes:
 
Maybe your shop wrote down the actual clearance somewhere on a workshop card.

Before you buy new valves, post a picture of the valve stem in question. You could have them spin the valves on a lathe to check for straightness, if that is what they're concerned about.
 
I've bought some Black Diamond valves from JS and it's suggested I ask if anyone here knows what valve to guide clearance to use with iron guides?
 
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I've bought some Black Diamond valves from JS and it's suggested I ask if anyone here know what valve to guide clearance to use with iron guides?
If you have a micrometer , measure the stems , i:e 5/16 or .3125 is the standard stem size for guide so "depending what their ground" to , intake stem might be .311 and exhaust might be .3105 .
 
I've bought some Black Diamond valves from JS and it's suggested I ask if anyone here knows what valve to guide clearance to use with iron guides?
Hard to go wrong following the factory spec. Norton specifies .3105" - .3115" for the valve stem, and .3135" - .3145" for the guide ID, same for both intake and exhaust. Black Diamonds are specified at .3107" stem for both intake and exhaust. So you could get anywhere between .0028" and .0038" clearance with new KPM valves and new iron guides. FWIW, Smokey Yunick recommended .0025" on the intake and .003" on the exhaust for cast iron Chevy guides. I've used that as a minimum criteria with success on Norton heads with iron guides and KPM valves. I use HSS or Cobalt steel reamers for cast iron and cobalt steel reamers for bronze guides, with a Goodson guide hone for finish. Reaming bronze guides is a good way to dull a reamer if not done carefully. Goodson sells a reaming oil specifically for bronze guides that really works. I've never tried bronze guide liners, but they obviously work quite well. I've also never tried diamond hones, but I don't expect to do enough more valve guide work in my lifetime to justify buying them. Maybe in my next life.

Ken
 
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Upon checking the timing inlet pushrod showed a .015'' bent:(
It is a good thing that you caught this. A valve with even a slight barely-measurable bend is a valve that's waiting to fail in service. Every time a bent valve lifts off its seat and then returns to the seat under spring pressure, it's the equivalent of bending a cheap wire coat hanger back and forth. A loose valve head from a fatigue-broken valve is a dead-sure day spoiler.
Sorry to have to say, but I would not feel comfortable with trying to straighten and reuse such a valve -- I'd replace it for sure; additional expense, yes, but not nearly as expensive as a broken valve going down the road.
 
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