I can't figure out what bolt could fit this hole in my LS1 Corvette oil pan:

M16 bolt seems just a bit too thin

Looks like maybe a plug?

 

Not sure this one fits:

https://www.summitracing.com/int/par...atedkitscombos

 

Could that be a sensor hole? Maybe oil temp or level.

 

I don't know, there's the same kind of hole on the other side of the pan but that one has a plug inserted on mine

 

Oil level sensor?

 

Nope,the oil level sensor is towards the back of the pan on the side-you can barely see it in that picture. I had a look at the batwing pan sitting on the shelf here and mine doesn't have those holes,wonder when they were added or deleted?

 

Turbo drain back??

 

oh yea probably that, i'll have to retap to metric