[Jacques Reed]

Hi Phil,

If it were not for the acetone and ATF mixture I would go with heating up the valve with the good old oxy-acetylene torch, if you have it. It is amazing what oxy heat can do with frozen items after they cool down.
Perhaps if the acetone has all evaporated and you are reasonably happy, and outdoors, it might work. All depends how dirty the engine is too. Keep an extinguisher handy just the same. Once the stem expands with the heat and cools it may break the bind.
Is it the mushroom stem ends or straight shank later 8BA type?
Once you get it free I suggest you drive the guides down and out rather than pull them down with the valve lifter bar. I learnt the hard way that the valve guide lip is brittle and broke one before a mate gave me this vintage Australian made valve guide knockout tool (attached). All you do is raise the valve after removing the collets or keeper, put the spoon end under the valve head onto the guide and whack the end of the tool with a decent hammer.
No doubt there are new ones on the market or you could rough out a similar tool.

Best of luck but in any case play it safe if in doubt using oxy.

Cheers,