rod bearings

[ricot83]

hey guys i need to replace my bearings, but not sure what size/clearance i am supposed to get or anything, i just rebuilt the oil pump and still have low oil pressure, also is this a permanent fix or temporary or what? in other words am i wasting my time?

[Eagle]

Look on the side of the engine block, near the distributor. You should see a boss with a recessed square drive plug in it, between the distributor and the oil filter housing.

Look for a letter or two letters stamped into the metal boss just above the plug. These give the bearing clearance codes. Not certain if they remained the same after Chrysler took over, but for the Renix years the codes were

B = Bores (Rings) 0.010 oversize

M = Main bearings 0.010 undersize

P = Rod bearings 0.010 undersize

C = Cam bearings 0.010 undersize

If you have no codes, all bearings are "standard."

[Sarge]

What size you'll need will be determined by how worn everything is. If anything needs turned that would mean different sizes other than stock.

Sarge

[ricot83]

thank you gentlemen

[Dr. Dyno]

hey guys i need to replace my bearings, but not sure what size/clearance i am supposed to get or anything, i just rebuilt the oil pump and still have low oil pressure, also is this a permanent fix or temporary or what? in other words am i wasting my time?

Use Plastigauge to measure all of the main and rod bearing clearances. Make a note of each and then you'll know what undersize bearings to buy.

[8Mud]

The connecting rod bearings, rarley wear round, they get kind of egg shaped. The largest clearnace is the middle of the top bearing sleeve.
If the machined surfaces aren't scored (or have ridges), new bearings will probably work out for you. If they have ridges, chances are the whole works is gonna overheat and self destruct. The oil leaches/washes away some heat, the crank, heat sinks it's share also. The ridges get hot fast. In an ideal world, there is a constant film of oil betweeen the machined surface and the bearing sleeves.
Most times if you can see the bronze/brass bearing through the chrome alloy coating, it's sure enough an indicator they are pretty worn or will probably fail soon. You can spot check a few with plasti gauge. I usually check number three and five first.
I alway use plasti gauge to check my new bearings also. Nothing will cook them faster, than not having enough clearance. I'm not very trusting.
The bearings sometimes wear more on one edge of the machined surface than the other, a good caliper gauge/micrometer check may save some grief.
Sometimes a little luck helps.

[8Mud]

Covering up the connecting rod studs with a piece of rubber hose, if you don't have the plastic covers made for the purpose, is a good idea. Cutting the rubber hose a little long also helps, something to grab onto with a pair of pliers. Nicking the crank with the studs, can't be good and happens quick.
I've never had a psiton low enough to see if a ring will pop out the bottom, maybe it's possible maybe not. Something to keep in mind though.