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O rings or no o rings? Checking ej25 main clearance

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So I’ve put together Engines by checking the main bearing clearances both with and with out the o rings in between the case half’s in the past and both engines were fine. But this time around I’m building one that is definitely going to have a big increase in power compared to the stockish engines I’ve built in the past and want to make sure that I am indeed checking my main clearance the right way so that there aren’t any problems down the road. So I got a question for ya Andre. When you assemble Subaru engines what is your preference when it comes to checking the main bearings? Do you use the oil o rings in between the case half’s? Or do you assemble completely dry?

I actually have another question as well. I am using king xpg bearings and I wanted to know if it is ok to mix shells for the main bearings? I believe I am going to have to use one std and one std x for extra clearance as they are a little on the tight side. I read somewhere that the only way you can do this is say you put the std bearings in say the RH case half then all the std x ones in the LH case half. I gotta look at my notes but if I remember correctly only 3 of the main journals are a little tight. Can I safely mix std and std x with out changing one whole half of the block to the std x ? Like journals 1,2,3 std x then 4,5 std on one of the case half’s? I know you can safely do this for the connecting rods but I am unable to find a clear answer for the main bearings. And if anyone were to know you would be the man Andre! Thanks for everything!