Its more than likely your correct size you need for that specific head + block

 

B20 cylinder walls are plenty thick to rev and make very decent naturally aspirated power. As long as the rest of the bottom end is built properly, you will have no issues. Use a new oil pump, balance the rotating assemble, make sure your piston-to-cylinder wall clearance is correct. Many people have had reliable NA B20VTEC engines rev to 8500+ RPM.

What I would do, for the block:
84mm Type R pistons
ARP rod bolt RESIZE THE RODS
ACL or King rod bearings
Balance the rotating assembly
New water pump, oil pump

You should have no issues revving to 8400 with a block built like that.

 

I'm running:

84mm JE pistons.
Eagle rods.
ARP rod bolts & mains.
ACL bearings.
brand new b18 timing belt and water pump

 

Don't use the ARP main studs.

 

why?

 

They won't improve anything. You have to line hone the mains afterwards and deal with bearing clearances. Factory is more than sufficient.

 

explain why you would have to line bore/hone the main journals when using arps?

 

Well I'm not taking the ARP mains out to put the stock ones back in because its already all together.

Is it going to be a prob?

 

thats what google says, ARP doesnt say you need to line bore the mains

 

When you torque any fastener more than the factory spec. it deforms the clamping areas (does that make sense?). Just like when you use ARP rod bolts, you have to get the bearing surfaces machined to make sure they are perfectly round again. I wouldn't use them, unless the machine work has been properly done and the bearing clearances have been rechecked. If you want another opinion, just ask an engine builder. It very well could be a problem.

In the end, it's your engine. Do what you want.