After pulling the crank to replace the main seal I noticed the #2 rod bearing looked like the coating had smeared for the lack of a better word. The motor has maybe 10,000 miles on it if that. The coating hasn’t yet worn off any of the bearings. I took some 1500 grit sand paper and sanded it smooth. You can still see some lines but can’t feel them. Thoughts on running it like this? These pics were about half way through the cleaning up process.
You know, its been so long I forgot you could buy just one. Now again, since its been so long, I can't remember if the crank was turned.
The bearings should have STD. or .010 stamped on them to tell you whether the crank has been turned. I say "should"..... Sometimes it stinks getting older!
A “before” pic would have been helpful. I’m thinking if it smeared, it’s lack of oil or it’s too tight. Maybe JW will respond.
What number rod is that.7,8? Looks like it ran dry and started to come apart . Replace it. How does the crank journal look?
Top & bottom bearings are a wipe out. Mike the crank in at LEAST 4 places. Show us a pic of the crank journal from a few diff. angles.
That bearing shell is toast. Check your crank pretty closely to see if there was any material transferred from the bearing to the crank. I'd also want to get to the bottom of the lack of lubrication on that rod. How was the other bearing on that crank throw? Do you know what the clearance was on that specific bearing when the engine went together? When you replace the bearing, you'll want to know what it is for sure.
The crank is absolutely perfect and the #1 bearing is fine. This was the only time I ever let someone else screw a motor together for me so I have no idea what the the clearance was. I'll be plastigauging the new bearing and all the rest. I'm in a jam because I'm losing the space that the car is in and have no choice but to put it back together with a new bearing and hope for the best.
Were those bearings coated in the aftermarket with anything? If so, then the coating is de-laminating. If not, then that looks to me like classic acid etching.. this typically comes from long term storage with dirty oil in the engine. But you typically see this to some extent on all the main and rod bearings... not just one. Although the classic indications are not present, with distressed rod bearings, we are always worried about detonation issues. If your combination is boarderline, normal variations in air and fuel distribution in the engine can lean one cylinder out enough to detonate just that cylinder. Tell me about your combo. JW
Hey Jim, I don't know about coated in the aftermarket. They just have that flat looking silver coating and that is what appears to have smudged. The did sit for over a year although I did start it occasionally. Only briefly though because of the massive oil leak. Don't remember exactly but its around 9.5 to 1 compression.
Im assuming the "other half" in your pic is the upper shell, being the first pic shows the shell in the rod cap. The upper bearing shell takes most all the load from the rod and piston, I'd be suspect of the clearance on that one. May want to pull the crank
Look at the rod cap and rod , the impression of the lettering and numbers on the rear of each Bearing shell should look like it's been clearly stamped in, if not and it looks smeared then those Bearing shells have been moving either due to not enough Bearing crush, getting hit with detonation, or a combo of both!
Smearing of the dark gray breakin coating most bearings come made with is a sign of a dry start or running dry , or lube break down at some point. Many builders choose to remove it in the first place so it does not wad up like it can at times which eats up the needed Bearing clearance at those locations on the surface. Also do not for get that the rod bolts themselves can be used forever and expected to provide the needed Bearing crush force. In a pure street motor ( that never see's more then 5000 rpm ) if they have been torqued up 5 times and not replaced then your just begging for trouble! If the motor has been rebuilt just once and during that rebuild the rod Bore got checked for size then those bolts have already been torqued up and stretched 4 times out of the playing with Fire 5 time absolute limit! Here's the numbers. 1) the rod is made at the GM factory and sized, that's 1 torque up session. 2) the rod is split open so the motor can be assembled at the factory,which is torquing them up a 2nd time. 3) you are rebuilding the motor and have the machine shop check the big end for roundness, that's a 3rd Torque up session. 4) You or the machine shop assemble the motor which makes for a 4th and maybe fatal time that the bolts are torqued up and stretched out.
