PJRiter

First Start after 25 years
Should I remove the valve covers and oil the rocker arms (425 not started in 25 years)? suggestions

oldcutlass

Its better to use a priming tool (basically a modified distributor without a cam gear) and prime the whole engine.

matt69olds

Or use a 5/16 socket an a long extension, spun by a drill. Make sure to tape the socket to the extension, it’s real easy to knock the socket loose and have it fall down into the engine.

Oldsmaniac

Make sure you have good gas and not a tank that has varnished.

Sugar Bear

The methods described above are the best because pulling the valve covers only oils a limited number of components. By priming the oil pump all of the internals that are normally lubed get oil except for maybe the wrist pins and the complete albeit partial part of the timing chain.

The second best way would be to remove the oil filter, fill it with clean oil, reinstall, drain the pan, add the needed 4-5 quarts then remove the coil wire and crank the engine until the rockers show some oil. It's difficult to get a lot of oil up top.

Whichever method you choose add a teaspoon or so of oil to the cylinders and make sure the engine turns freely and completely by hand before using the starter.

YMMV, Good luck!!!