This is a small concern ive had since i built my engine 2.5 years ago. I sized it all out for high rpm, boosted application. Its a b18a1 with eagle rods and srp pistons, oem bearings. I specd out main journals 1,2,4,5 to .0018 and journal 3 to .0022. My rod bearings are all at .0015. Does having the slightly tighter clearence on the rod bearing cause any issues like premature bearing failure? Oil pressure is perfect and i see around 70psi@4000rpm once its all warmed up using 5w-30 (though typically i run 10w-40 due to the high oil temps i tend to have when running such high freeway rpms)

Engine has been rock solid, but im only spinning it to 7k since im using a stock head while i plan out rebuilding my other head. The new head will spin up past 8k (nonvtec head) so i wanted to address my concerns before hand. Engine has 35k miles on the clock and besides little things (carbon fouled and damaged a sparkplug caused by a bad valve guide makin the cylinder burn oil) the engine mechanically has been sound.

 

I'm a noob when it comes to building and lack experience, but I've been reading a lot lately. I'm looking forward to hearing responses from the experienced builders here. Seems to me that as long as you have good oil pressure, which you do, there shouldn't be any problems. People say "loose is fast", but I would also think you'd want the rods to be on the tighter side of spec to keep your side to side rod play to a minimum. But then again, what do I know...

 

Side to side play doesnt change a significant amount when you change the bearing size i dont think. Regardless all my side to side play and crank end play are spot on perfect.

 

I say run it!

 

I don't have the B18 FSM manual but I am pretty sure you are within spec on your bearings. You've been running them and your pressure sounds perfect.

If anything, I would change to Pennzoil Platinum Synthetic 10w30 so you are running in spec oil that has superior shear and high temperature resistance and lets you run 10K between oil changes without issue at all.

If those clearances match factory spec, then I'd say you are great to go. OEM bearings last a very long time of 300K KM or more before hitting the first soft layer of copper.

If you are concerned then start doing oil analysis of every oil change. After 2 or 3 changes you have your base line and when the copper shoots up some years down the road, you know it's time to finally redo the bottom end. OEM bearing use a copper layer from what I've seen.