Have had #6 cyl valve bend twice (stainless in a Merlin Head) any suggestions ?

ck piston to valve clearance

Stunt,
It is possible that either the valve guide clearance is too tight, or there might be something causing that combustion chamber to run a lot hotter than the others. A bad injector, vacuum leak, carb problem, ignition wire crossover etc can cause the combustion chamber temperature to be too high in the one cylinder, which in turn will heat up the exhaust valve more than nomal, causing it to expand and stick in the valve guide. The spark plugs will probably tell the story.

I doubt that it is a valve to piston problem if it is only that one cylinder. You need to have your machine shop measure the valve guide clearance snd make sure it is correct. I would almost guess if it has stuck the valve twice, it might need a new guide.

Without looking at the parts that is all I can offer ....

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I agree with Bill. Sounds like it's hangin in the guide. Can you see where it's tagged the piston? I assume that it's an intake valve (stainless). Hopefully your running Inconel exhaust valves. In a high performance marine application you have extreme high exhaust temperatures.

What valve to guide clearance are you running? what style seal? is water leaking into that cylinder?

I agree with Billk, if it's a EFI set-up #6 is allways the cyl I try to tune to. If there is a lean condition it will show up there (#6) first. You may be having a fuel related problem.

My money is on bad machining from merlin. I had a set they didn't machine the top of the guides off correctly. Spring retainer contact = broke timing chAIin. They suk.