What size connecting rod bearing?

[Dngrsone]

I am overhauling a 1988 S-10 Pickup 2.8 liter engine with a spun connecting rod bearing on #1 cylinder.

I have the heads off, ready to start pulling pistons (I have full sets of pistons and connecting rods inbound), but I have no idea what size bearings to buy. I am looking at the list at Rock Auto and they show bearings ranging in size from .001mm undersize to a full 1mm oversize.

How do I determine the proper connecting rod bearing size?

Thanks for your time.

[silicon212]

You don't. Not in the way you want to. If you simply buy one bearing and replace it, that bearing will instantly spin the instant you fire it back up.

You're looking at a bottom-end rebuild, complete with all bearings, crankshaft, and probably a new connecting rod or two. There's also a chance you need to replace the affected piston, due to the possibility that the increased bearing clearance allowed the piston crown to make physical contact with the cylinder head.

[Dngrsone]

Thanks, silicon, I knew I would have to replace all the connecting rod bearings, and I am replacing all the rods and pistons (fortunately, the piston did not hit the head, but I broke it trying to get to the bearing ).

My question is, how do I determint the appropriate oversize for the replacement bearings? I don't want to guess.

[silicon212]

Originally Posted by Dngrsone

Thanks, silicon, I knew I would have to replace all the connecting rod bearings, and I am replacing all the rods and pistons (fortunately, the piston did not hit the head, but I broke it trying to get to the bearing ).

My question is, how do I determint the appropriate oversize for the replacement bearings? I don't want to guess.

Depends on what crank you get. If you get a common 'ten-ten' crank, then you will be using .010 undersize bearings. Your machine shop will tell you exactly what you need to use. I don't know about over there, but my machine shop marks the crank with a paint pen for what it is - one mark on the counterweight and one mark on the rod journal throw is .010 under mains and .010 under rods, one mark on the counterweight and two marks on the throw would be .010 mains .020 rods etc.

[Dngrsone]

Originally Posted by silicon212

Depends on what crank you get. If you get a common 'ten-ten' crank, then you will be using .010 undersize bearings. Your machine shop will tell you exactly what you need to use. I don't know about over there, but my machine shop marks the crank with a paint pen for what it is - one mark on the counterweight and one mark on the journal throw is .010 under mains and .010 under rods, one mark on the counterweight and two marks on the throw would be .010 mains .020 rods etc.

So you're saying I can't reuse the existing crank?

[vesmcd]

When you spun the bearing, it messed up the bearing surface of the crankshaft. If you don't have the crank journals reground, you will spin the new bearing as soon as you fire up the engine.

[Dngrsone]

Yes, the journal is scarred. I am pulling the crankshaft out for machining. Thanks, guys.