Help what size bolt goes in here?

I have a Elite Engineering Oil Catch can they make them for Corvettes. I got it real cheap but to install it I have to bolt it into a hole in the engine block. So if any one knows what size bolt goes in hole that my finger in pointing to I would be grateful. Thanks advance.

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220....221....whatever it takes.

Seriously, check out a few Metric sizes.
On my truck, half of it is SAE; half is Metric.

Tough to tell from the pic, but it looks like it's about 6mm or 8mm.
If it's SAE, try 1/4-20, 5/16-18, or 3/8-16.
All should be available at your local home improvement store for a few cents each.
Return unused portion to fill your pocket with change.

 

PM Sgt. Stanko. He makes a catch can bracket that I believe threads into that hole too.

 

NOW THAT'S THINK WITH YOUR DIPSTICK. LOL

 

I did as you said and found the bolt the problem I have it but do not know the size. So tomarrow I will size it up at work and let you guys know. Thanks for the idea!

 

Ok it is 18 mm I got the catch can on now I need hoses lol. Once they are put on I will take pics of it. So you guys can see it.