Run the engine for 30 minutes after reaching operating temperature. Then turn off the engine and adjust the valve lash.
Post the serial number that in pressed into the ledge to the rear of where the distributor enters the block.
Here are the 1956 235 codes. All 235 truck engines had solid/mechanical lifters and all 1956 and later 235 passenger car engines had hydraulic lifters.
You might by able to turn the crankshaft be hand by trying to rotate the harmonic balancer, or by trying to move/rotate the fan belt.
This type of flywhell rotating tool will do the job. Last resort, if you need a tool: take the bottom cover off of the clutch housing and pry the flywheel with a strong/large flat-blade screwdriver.
