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
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.
Yes, you get a shop to hone them or if DIY you have to use this type but for 8mm.
www.hogparts.co.uk
Yes , KW warns against carbide and high speed reamers with C630
Yes, this what happened. If I could I would insert a photo of the piston top
Upon checking the timing inlet pushrod showed a .015'' bent
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
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 .
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.
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.Upon checking the timing inlet pushrod showed a .015'' bent
