Brother of The Benz,tsgtchew
There are procedures for storing an engine and for bringing it back.
It does no good to tell of that now.
You may have the piston rings not sealing after having set for such a long time.
Valve stem seals may have become attached (stuck) to the valve stem and when put in motion may have become damaged.
These are a few of the pitfalls of storing an engine without properly preparing it.
Change the oil and filter.Use a motor solvent with the motor oil.
Add a solvent such as Marvel Mystery Oil or Risolone in the spark plug holes and turn the engine over using the starter motor.
Let it set a while, this will help if the piston rings are stuck.
With the engine running, air filter removed, pour the solvent in the intake, flooding the engine but not letting it die.
This will deglaze and lubricate the valve mechanics.
After all of this, time my help.
Try running the engine mildly and driving moderately.
Take it easy for a few miles to allow the engine to fix it's self.
After all of this hot air, all that remains is,
Happy Trails Beep Beep from The Spiderman in Houston!!!