Oil Pressure Relief Valve

I've bought a nice shiny new SS oil pressure relief valve, that's the end of the good news.

Can I get the old one off? Nup....

Any tips? Are these usually difficult to persuade off? Should I take the casing off and warm it up or something?

d

I haven't had that particular problem, but many similar ones...
Every time without exception, a good dose of heat has won the day

I would think (been doing that too much lately) that if the timing cover was mounted to the engine you could easily loosen it with the huge wrench that fits the hex.

If you have the cover off I'd screw it down to a piece of ply wood with sheet rock screws, leaving the offending hex(s) over an edge, at that point I'd use the box end of the wrench and have at it; something will give and rather quickly...

RS