All 4 inlet valves on my 1938 Ruby are stuck.So I took all 8 valves out and cleaned them as it hadn’t been done since the 80’s. The exhaust ones were fine, but I still cleaned them and lapped them in. I put the head back on along with a new gasket, and stared the engine. It started first time, and run lovely. I let the engine run for 10 mins then turned it off. After about 15 mins I decided to start the engine to take the car for a run, but was horribly shocked to find all the compression had completely gone again. And cannot believe it! When I cleaned the valves they were free as they should be…. I cannot understand it. It is only the 4 inlet Valves that are sticking….. Could it be new guides?
I have just been advised by a friend unable to reply direct to your posting that he had a similar problem. He found that his petrol tank had been lined many years ago and that the ethanol in modern petrol was dissolving it. What he found was that after running the engine for a while after it cooled the residue in the fuel had formed around the valves and caused them to stick open.
He would be happy to explain more if you wish to contact him, his email is firstname.lastname@example.org
I notice you mention new guides. Have you fitted new guides? If so did you ream them?