I just had my head gasket replaced. Why is my car knocking and surging up and do

Car started sounding bad and smoke was coming out exaust pipe. My Mechanic replaced head gasket, resurface cyl head, grind valves, replaced spark plugs. He said there was no oil in the engine and there could be possible damage. $900.00 later it shouldn't be knocking and surging should it? He said to bring it back if there was a problem. What kind of problems would I have if the engine was damaged? I really appreciate your help as I am a widow with no one to consult with. Thanks in advance for any help you can give me.

The part about there being "no oil in the engine" and "there could possibly be damage" is the part that is popping up right now. It's terribly disappointing and sad, but you have base engine issues, probably due to lack of lubrication. Your cylinder head is probably just fine now, but your pistons and bearings in the engine are likely compromised. I'm so sorry to hear about your situation and would encourage you to work with the mechanic towards a reasonable solution, holding them partially accountable for not checking the engine fully before selling you the repair work.

Dave, I took my car back to my mechanic today and he adjusted the timing belt I think. It runs quieter but it is still blowing smoke. He said to bring it back in and he will check it for me. Do you think I should have someone else check it? Thanks for your help Trisha

To me, it needs to go back to the person who did the repairs first, for every possible attempt. If you go somewhere else, it will cost you more money right off the bat. I still feel like you probably have a base engine issue, but definitely see what you can do with the mechanic who did all the work of record first.

Thanks Dave I'll do that. Is there any test that can done to test the basic engine. Can I keep driving it with some smoke?

If "some smoke" is the only symptom and you still have good power and no noise, then yes, you could drive it until the point you may require an emissions test of some sort. At some point, though, it will continue to deteriorate. I would focus on a good solution for all your money spent.