Oil Pressure Relief Valve Plungers Frozen

[Ashley James]

I have a second engine for my car and am in the process of rebuilding it. It's a 64SC and both relief valve plungers are stuck solid. No obvious signs of corrosion, but the engine has been in bits for a long time.

I've tried soaking for 12 hours in vinegar or penetrating fluid and I've applied hear with a hot air gun, but they're stuck fast.

Does anyone have a trick or know something I don't. There must be millions of the latter.

[Dave Erickson]

Try using a tap to pull it. I think a 10mm tap fits, but I'm not at home to check. Just get the tap to bite and you should be able to pull the piston right out.

[Ashley James]

Good plan, I'll give that a try.

[Vic Skirmants]

Pipe thread tap. It will eventually bottom out and turn the piston. I think 1/4" pipe; not at home to check.

[John Brooks]

there is a P tool for that, but the tap is easier.

[Ashley James]

All done with a 14mm 1.25mm pitch 2nd tap and a hot air gun. Thank you all for your help.
It's a relief that no harm will have been done.