Just put 70 440 r/t challenger back on road after 15 year rebuild. Temperature gauge hardly gets off cold. I would like to put in a mechanical gauge to see what it is reading but the 1/2 plug does not want to come out. Engine is freshly painted so really don't want to use torch.
Is there a superior Penetrating oil ?
thanks
Gregg

Kroil

Yes Kroil or PB blaster

Home made mixture of 50% ATF and acetone works GREAT

i seriously doubt any of the suggestions will work as pipe threads can be very stubborn and some of the Suggestions will most likely eat or discolor the paint. Which 1/2" plug are you trying to remove ??

Got a pic of it as there are several different types and the approach may change depending on what your dealing with.

Aluminum or iron manifold? If aluminum, it's not coming out.

Be a hell of a trick to get a water temperature sender to work in a 440 intake.

I think you meant water pump housing

As for the paint, doesn't really matter it's going to crack when you pull the plug out, if you can. May as well accept that.

My bad, I sit corrected.
I found it impossible to remove a steel pipe plug from my SB aluminum manifold.

If the penetrating oil over several days did not work then I would use a torch & some candle wax.

Is it the OE sender that is stuck or one of the other suitable plugged ports on the housing? No harm pulling the OE sender for diagnostic if that is what it takes.

Good luck if pulling an OE plug in an iron housing without lots of heat.

I took out the original sending unit out but hole is to small for mechanical sending unit .. There is a 1/2" plug by the 2 hoses that go to
the heater core.