What does normal wear on a main bearing look like?

I pulled two main bearing caps on my 400 SBC to inspect them.

About 2 inches in the center of each of the bearing looks copper colored. They are smooth except FOR at one end of each bearing where for 1/4" they felt slightly rough, Considering the rotation, that would be the end where any debris would collect. The crank looked perfect.

Anyone have any pictures of normal bearings or thoughts? Is this normal?

thanks

FYI - changing a motor in my COE is becoming a real pain in behind!!! I'll post pictures later.

 

Copper means the bearing is worn out. It has worn through the babbit to the copper backing.

Check the crankshaft for wear, measure with a micrometer, if it is round, smooth and not worn down you can just replace the bearings but chances are, with that much wear, the crank needs to be turned.

 

Well isn't that just wonderful news...

 

That's normal wear. But it is wear....you probably want to replace them, and either mic the crank, or at least check the clearance with new bearings using plastigage. The bearings are a lot softer than the crank, so they usually wear more.

 

Ugh!!!! I really don't get along with bearings, never have...hate the dumb things and they hate me back twice as much.

It is possible to replace the bearings without totally tearing the motor to pieces? I have the new cam and heads already on it and hate to tear it apart again.

 

Yea but it ain't easy. Gravity won't be helping you, you'll be fighting it. If I was an evil bearing looking to get you, I'd wait until you were under the car fuckin with me.
Start with the bearings next time.

 

It's a lot easier to do on an engine stand, with the engine upside down.

 

Rod bearings are easy to do under the car, but mains not so much. I've found that it's best with mains to loosen all the caps at once and then address them individually. I try to get them as loose as the thread length will allow by taking each one out, then just screw the bolt back in a couple threads. Once they're all loose you can remove one main cap, and then pry each engine side journal bearing out and replace it. Then loosely reinstall the cap and move to the next.
Of course mic the crank before even buying the new bearings, just so you know it's good.
Make sure you do the rod bearings too while it's open. They're cheap (even for high quality) and not worth opening the engine for later.

 

I checked a web site of bearing pics and mine look like normal wear.

http://www.bobistheoilguy.com/bearingwear/bearingwearanalysis.htm

A friend told me that I should remove the main caps one at a time, lightly pry up on the crank and "roll" the old bearing out and "roll" a new one in. He suggested just replacing with bearings with the same size that are there now. He said to do them one at a time so I would know if one was too tight and to use platigauge on a few to make sure thay are not too loose.

Thoughts?

 

How do you measure the crank mains in the engine? Or are you just talking about the rod bearings?


FYI - my motor is still hanging by a chain so I can flip it around.

 

That sounds like reasonable advice. Make sure you figure out what size they are, usually they're stamped on the back side something like 010 and that is the undersize in thousandths of an inch.

Measuring the mains with the crank in the engine is pretty much impossible, so check the clearance with plastigage. if it's less than .003" youre fine

 

A trick I've used is to remove the bearing cap, stick a nail in the main journal's oil hole, then turn the crank to roll the top side bearing out. The nail head will push the bearing right out of the block. Be sure to turn the engine so the nail meets the bearing on the side without the tang. Doing it that way avoids any prying or potential for scratching the crank journal.

 

In order to plasti-gauge the main bearings, you need to unload the down weight of the crankshaft. To do this, you need to put a jack on the crankshaft counterweight and jack up the shaft to push up the clearnce on top. Then you can use plasti-gauge to check the clearance. Without jacking up the crank, you will get a false reading.

 

Good trick to remove them...Any trick for putting the new bearings back in?

I was loking on Summit Racing site - lots of choices, what do I want for a mild street engine? Are the bearings sold as pairs or full sets?

 

Jim, Are you saying I should measure the old bearings with plastigauge first to see if there is too much slop?

 

I was suggesting checking the clearance on the new bearings.

Rod bearings are sometimes sold as pairs, sometimes as full sets. Mains are sold as full sets. You want normal bearings, usually the Clevite 77 or equivalent. Should cost around $80 for rods and mains

and you need to make sure what size you need before you get too far along.

 

I will pull one rod and one main cap off and and check the numbers on the backside and then mic them too.

White lithium or just engine oil for reassembly?

 

Either...or the assembly lube that the bearing companies sell

 

Yikes, forget $80 for everything. The mains alone for the 400 are $70.

 

Underhauling diesels so done all the time. Old motors manuals use to show how to make a tool out of a cotter key. Take a cotter key and mash the eye shut bend the legs out at about 90 deg. and cut them to about to the width of the bearing. You will need to tweak the legs the loop part goes into the crank oil passage and the legs lay flat against the crank. Put the key in the oil passage and turn the crank so that it comes against the nontang side of the top bearing half keep on turning the crank and you'll roll the top half right out

 

inflation....it's been a year since I overhauled an engine.

 

Again...how do you put them back in? Bearings are NOT my friends. I totally destroyed my 51 Merc Flathead as a kid by messing up all the bearings, so I really need remedial instruction.

I am not ashamed to say. Bodywork and paint = easy, Engines = duh!?!??!

350 mains are $32, the 400 is more.

 

Damn, if it's on a chain just put it on a stand and make your life a lot easier. There really isn't a good way to mic the mains with the crank with in the block. Chances are if the bearings are worn, so is the timing chain & sprockets, so now is the time to change them too. Don't forget an oil pump.
Good money spent now will save you lots of headaches/money later on down the road.

 

The suggestion to loosen up all the main cap bolts will help, then you make sure which way the bearing fits, and put it on the crank journal, and then slide it around till the tank fits into the notch, and push it in the rest of the way. The cotter pin trick might help. It's a bitch to do it under the car.

If it were a big diesel you'd have more room to work...but a 400 especially is really tight.

 

Just oil them and they should roll right back in by hand. Be sure the tang is right.

 

Put it upside down on a stand...loosen all main bolts first...Remove one cap and rotate bearing out with the nail-trick, oil the new bearing and just slide it in until tang fits into notch. After all are done, torque them down starting at center working outwards in various stages up to 70 ft lbs. Right?

There are arrows on the caps, do they all point to the front or back?

Now for the cap part, Do I just pry it out with a screwdriver...or ?

 

Just start them in on the tang side and push them in with a screw driver or to be safer a brass drift Back in the 60s they used to check crank finish by rubing a penny across them if no copper came off the crank was good but of coarse pennys arn't copper any more. I just did it on a 300 Ford in the truck. It helps to have 2 people 1 to hold the bearing and 1 to turn the crank.

 

X2 and the rings.

Put the block on the stand.
Mark everything.
Take the heads off.
Cam and lifters out
Get the autozone ridge cutter ( free rental)
Take the pistons out
Crank out.
Mic all that stuff and the bores.
Should all be within reason and ready to put back together without a machine shop.
Clean your pistons up and the grooves.
Hone the cylinders. (3 stone is free rental too )
Scrub it down.
New rings, rod bearings, crank bearings, oil pump , and gasket set is available as a kit cheap. 200.00
http://m.summitracing.com/search/ma...ype/engine-rebuild-kits?toggleResults=display
Put it all back together.
One good Saturday should do it if you have everything there.

You could just put bearings in it, but you can't hardly clean anything.

 

On the two main caps that I took off, the crank looked just perfect, but I bet I can find some copper penniies around here. Wonder if copper pipe will work?

 

There is no ridge. The motor was rebuilt recently. It was bored .020 and new pistons installed. I put a new cam, lifter and double roller timing chain on it already. I also replaced the heads with a rebuilt set too.

I just pulled the pan to put the new timing cover on it and decided to check some bearings. It apparently shows some normal wear. It was a running motor before I started all this. The cheepie aftermarket gauge in the donor car showed 25psi oil pressure at idle, went up to 60 reved.