I built an LS3 based 427 last year for my truck and its been running great. I used King PMax Kote bearings in it, but since I wanted to beat on it and not worry I built it with .0005" extra oil clearance in the mains to keep things cool in the bearing department. I used a HV/HP oil pump to compensate and it idles at 40psi hot so it worked out well. When I did that I used a X .001" larger bearing half and a STD bearing half together. I didn't think about it at the time, but does it matter what position the X bearing half is in? Upper or lower? I'm about to put my LS7 bottom end together for my Z28 and am paying a little more attention to this assembly. I haven't found much on this subject other than its normal to swap bearing halves around, which I already knew. Do I just need to keep all the STD and X halves to one side? Does it matter at all? I've built probably a 120 engines but the lifter failure from this engine before has me paranoid about everything now. I'm not cool with dropping another 25k into this over a bearing half....

 

YES, It does matter. They need to be the same size shell on the block side. Same with the cap side.

If I recall , you want the X bearing with more clearance on the block side in this application because the block will grow more than the caps.

@Che70velle Please correct me if I am wrong.

 

Its honestly a preference thing. I always put my larger sides on the caps…rods or main caps…if I’m half-shelling. But whichever way you decide to go, you MUST do all 5 the same. Triple check here at final assembly and make 100% sure you have them set up correctly.

 

Thats what I did on my trucks 427. I'll keep doing that. Thanks