Working on engines will require some special engine repair tools. If you are doing repairs that do not require anything more than removing the cylinder head, then except for a torque wrench a typical mechanics tool set should be all you need. A lot of modern vehicles require special tools such as Torx sockets, for certain fasteners. This will strictly depend on the engine you are working on.
As crazy as it may sound, now days one of the best tools you probably already have is your cell phone camera. I regularly will take 20 or more pictures of an engine before I start to disassemble it. That way I will know where all of the brackets and other parts go. I do the same thing with cylinder heads that customers bring with everything still bolted on them.
If you are working on an engine with camshaft(s) in the cylinder head(s), then you may also need a camshaft alignment tool to hold the camshafts in alignment while reinstalling the timing belt or chain. There may be other special tools you need for working on your particular engine. They should be described in the service manual. Some auto parts stores have these special tools to rent. Others might even have a loaner tool program where you can leave a deposit and “borrow” the tool to use.
If you plan on completely rebuilding your engine, you will need an engine hoist to pull it out of the car. You will also need some additional special tools. Once again, a torque wrench will be needed. A piston ring compressor will be needed to install the pistons in the cylinders. A piston ring installing tool will be needed to properly install the rings on the pistons.
At least two micrometers are needed. One that will measure the size of your pistons and one to measure the crankshaft journals. If you are very comfortable with your Automotive Machine Shop, you can trust them to do these measurements for you and then simply assemble the engine, but anyone can make a mistake and the final responsibility really rests on the engine builder ( You ! )
When purchasing tools for engine building, especially measuring tools such as micrometers, it is best not to look for the least expensive ones available. High quality tools will last a lifetime with just a little care.