You did not indicate how many miles this engine has and how often oil has been changed.

I would expect that the valve noise is due to gunking up. The best way to cure this is to use a Universal grade oil and change oil and filter about every 500 miles, draining it when hot, until the noise goes away. Universal grade is specifically for diesels but tested and certified for gas engines as well. It has an EXTREMELY larger amount of detergents than other oils and will SAFELY clean out a gunked up engine.

After that change to synthetic if you are running extended oil drain intervals.

More history of the car would be helpful in answering your questions.

Good luck,