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How to free up and remove a stuck exhaust valve? The head has been removed from the cylinder. I have had some ATF in the exhaust port, not for that long I suppose, and I have given it some gentle taps with a hammer (with a bit of wood between the valve tip and hammer) to no avail. Do I need to soak the whole head in something for a long period?

Stick the head in the oven when cooking the roast -about 170C, wip it out when it is warm and sizzling and then give the valve stem a gentle twonk with nothing retricting the valve head underneath, give the stem some diesel to aid lubrication. I did have a sticking valve on an engine with inclined valves which would stick open when giving it some welly, the piston would then close the valve - at tick over and on cooling down would then do as it was told.
Round where I live it used to be fairly common for farmers to have this problem with their Land Rovers caused by pootling around at tick over, the cure was an Italien tune up with chunks of glowing carbon coming out of the exhaust.

What Harrymuffin said. Shock 'n Unlock (combined freezing/penetrating oil spray) directed on the valve stem so far as possible is what I would try after heating.

Thanks for the suggestions. I don't think I would get away with using the oven so I will leave that option for now but Harry's mention of the diesel reminds me what others have said to me about diesel so I will get some and completely soak the head in it for a week or more and see if a gentle tap or two succeeds then.

stradella wrote:Thanks for the suggestions. I don't think I would get away with using the oven ...

A hot air gun should do it, the head is not very big so would not be too much of a heat soak.

Ming wrote:

stradella wrote:Thanks for the suggestions. I don't think I would get away with using the oven ...

A hot air gun should do it, the head is not very big so would not be too much of a heat soak.

Indeed, it's surprising how hot you can get things with a hot air gun. You could build a 'hearth' of bricks to help retain the heat.

If 'tut other half' won't let you do it with the Sunday roast then do it when she is out jogging. Someone might say, but if you heat the head up and have the original castiron valve guides, then you will knock the guides out - differential expansion, the original guides have spring clips so they can only go so far into the head when fitting new ones. The oven is the best way as the heat is uniform especially if you have a number to knock out of an alloy head, but if only one as you have, then hot air gum as suggested is just as good as using a blow lamp keeping the flame moving over the head as much as possible. Spit on it every now and then and if it sizzles then it is hot enough. If you have kerosene central heating then drain some out of the tank which is just as good as diesel Kerosene down to 19p a litre from the suppliers and diesel at the local garage now 94p/ltr, should I fill up now or wait another couple of weeks?

Success. Eventually I found a decades-old 5 litre plastic oil bottle and cut one side off. There was just enough space for the head. (Modern oil bottles with handles both at the top and side have a rectangular shape, too narrow to hold a 350 Morini head.) Filled it with diesel and left it for two weeks. Took the head out, cleaned it a little and tried to set up a press of sorts with a valve spring compressor in an upside down position along with other bits and pieces ... wasn't going to work.

Today I used a hammer and block of wood and just delivered repeated light taps and after perhaps 200 taps I thought I might be feeling some movement. Yes!

Got it out. Plenty of carbon around the valve head and lower stem but the problem, most likely, was some rust half-way up the valve stem. I am reasonably sure that this head/engine has done very low kms, perhaps only 16,000, so cleaning the valve and valve guide will hopefully suffice for some more klms - whenever the rest of the engine gets done ...