Motor mount nut size?

[polkat]

Trying to remove the nuts that hold the engine brackets to the top of the mounts (one each side) on my 318 poly in a '64 B body. Can't see too well in there but no wrench I've tried yet seems to fit. Looks like...maybe an 11/16". Does that sound right? Thanks!

 

[MarPar]

Seems kinda big for a 318...IIRC a big block is 5/8" :edgy:

 

[Meep-Meep]

It's possible the nut is 11/16" and the bolt head is 5/8"

 

[polkat]

I see. I'm talking about the threaded stud that comes up through the top of the rubber part of the mount. The brackets on the block have a hole at the bottom that fits down over this stud, and then a nut tightens the bracket to the rubber. It's the size of that nut I am asking about.