motor won't turn over

[Cobra Jet Steering LLC]

most likely you have an exhaust valve stuck open and a piston is stuck up against it. Pull off the valve covers and look for a loose rocker arm that will lead you to the valve that is stuck . You should always turn those engines over in the off season so your valves and valve springs don't have an issue.

 

[Lance Stiffler]

Plugs looked good. No evidence of water. And I've put marvel mystery oil in the cylinders and no movement at all.

 

[Lance Stiffler]

I've taken the rocker arms and push rods out. What next?

 

[Cobra Jet Steering LLC]

then it's easy look for a valve stem that is not all the way up most likely an exhaust valve also try turning the engine backward and see if it moves if so you definitely have a stuck valve. moving the engine backward gets the piston off the valve , hopefully you did not bend the valve when you first cranked the engine over.

 

[Cobra Jet Steering LLC]

Also there is a fitting that you can purchase fairly inexpensively or make one with a little ingenuity, it was what we used years ago when we needed to change valve guide seals without removing the head, This fitting screws in the spark plug hole and you attach your air compressor with 120 psi using a quick coupler like any air tool does , it pressurizes the cylinder , it was to keep the valve in place while you removed the spring however if you have an open valve you will locate it immediately when you charge that cylinder and you will hear where it is coming out in either the exhaust manifold or the intake manifold.