Technical 8BA Oil Pressure Sending Unit square nut wrench size

Sorry, sorry, I know this has been discussed to death, but I've seen conflicting info.

What size wrench fits the square driving nut on an 8BA oil pressure sending unit?

I've seen posts that say 9/16", and others that say 5/8". If somebody knows for sure, it could save me having to "double-90" the wrong size wrench.

 

Also, anybody ever tried using an open-end crowfoot wrench to loosen a sender? It's worth a try, but it'd help to know what size to get so I don't have to buy a whole set....because, according to the wife, I "already have every tool known to man!"

 

Just get a harbor freight crow foot set .

 

Well, she is clearly incorrect!
And I'll let you tell her.

 

OK. At $9.99 for a set, that's cheap enough even for me.

 

I just measured the one (original as far as I can tell) I took out of my '50 8BA this past spring. It's 9/16"

 

Use a 9/16 wrench works every time.

 

My '49 Tudor Custom, "Shirlene", and I thank you, sir. Did you install a new one, or did you install a mechanical pressure gauge in that plug (like I intend to do)? I like that blackwall look, by the way, that's what I'll be going for. Shirlene was a farm car, she never ever wore whitewalls!

 

Thank you, sir.
You got that sweet ride up to 200? Top down at the time, I take it?!

 

I put a mechanical oil pressure gauge, a volt meter and two mechanical temp gauges below the dash under the radio. I also put oil and battery idiot lights in the instrument cluster where the original oil pr. gauge and ammeter were.

The blackwalls with original style center caps and trim rings is a look I wasn't sure about at first. I've come around to thinking it was a great idea.

 

I did manage to get a 9/16" open end wrench on the square fitting, you were right...fits like a glove. Of course, there is no room to MOVE the wrench, but at least now I know what size crowfoot to try, or what size wrench to try to bend. Thanks again.