Time for my first oil change of my six conversion. I didn't put in a quick drain plug on my -16 AN hose as more fittings just meant more money at the time - figured I could do it later if I wanted. Seems my fitting on the oil cooler is blocked by the headers - so not so easy to remove.

I drained 6 quarts from my sump (car been sitting for a while) and.....drained 2.25 more quarts by loosening the oil cooler from the engine and cracking it a little. 8.25 quarts out of 11 put in when it was bone dry. At least 1 quart I'd never get out regardless. For my one oil change a year...I think I can live with this! Versus the major PITA of putting in a quick drain tee.

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I would not do it that way because you could damage the cooler with messing with that frequently.

Probably the best way is to do what the factory did--just unbolt one of the oil lines and let it drain out that way. And drain the sump using the drain plug in the bottom of it.

--DD

I guess I don't get it. .
Isn't that is what the middle connection between the oil tank hose and the cooler hose is for. . anyway that's what I do to drain the oil tank, and then pull the oil filter afterward to minimize any messy leakage there. .
I'd be more concerned you're risking getting some debris in the oil cooler to block seals and causing a real leak. .

As with a 911 you always want to drain the contents of the oils tank first...while the engine is somewhat warm. Then you can take the plug out of the sump plate to release the remaining oil that may be in the crankcase. I can think of absolutely no reason to lossen the oil cooler away from the case as you are. Not sure where you got this advice or idea but it isn't a good way or smart way to change your oil.

Yes.

30 yrs ago i put an aircraft sump drain in the bottom of my oil tank

you push it in - it drains

yes, you have to remove the tank to do this properly

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How does this affect the seal between the cooler and the block? I would think that it would lose its sealing ability and leak when not desired.

that would be my concern

You are asking for trouble draining your oil like that. You need to break down and put a drain in the oil line. Get two fittings, an AN T and a cap.

If it's stupid but it works - you have come upon the the definition of lucky!