oldschool90 Posted June 8, 2011 Report Share Posted June 8, 2011 Hey guys, I need to change the rod bearings on my truck, but I'm not sure what size to get. I had to get another re-manufactured crankshaft about a year ago, and I dont have any of the paperwork from it to see if they even put the bearing sizes on it. I dont know what to do now. (and if it helps, I got the crank from autozone). Is there any kind of markings on the shaft itself that they would've put for the size? Or am I going to have to pull the crank out to get it measured? Quote Link to comment
albyneau Posted June 8, 2011 Report Share Posted June 8, 2011 Hey guys, I need to change the rod bearings on my truck, but I'm not sure what size to get. I had to get another re-manufactured crankshaft about a year ago, and I dont have any of the paperwork from it to see if they even put the bearing sizes on it. I dont know what to do now. (and if it helps, I got the crank from autozone). Is there any kind of markings on the shaft itself that they would've put for the size? Or am I going to have to pull the crank out to get it measured? If you're just doing rod bearing you dont need to pull it unless it's really bad~ but you will need to measure it! Quote Link to comment
oldschool90 Posted June 8, 2011 Author Report Share Posted June 8, 2011 you will need to measure it! Thats the thing though, I'm not sure how to measure it. Plus also the most precise piece of measuring equipment I own is a ruler. Now that I think about it though, I think I might have a micrometer somewhere, but I dont know how accurate it is. unless it's really bad I'm assuming that you assume that the bearings are bad? One is. But only a slight knock. I'm hoping I can fix it myself with some kind of fine polishing compound and a little elbow grease. Quote Link to comment
datsunaholic Posted June 8, 2011 Report Share Posted June 8, 2011 Generally they don't mark the undersizes on the crank. The bearing shells themselves MIGHT have a size on them, if not standard. But it's best to measure. Rod journals can be measured w/o totally removing the crank. In fact you don't even have to remove the pistons/rods to change bearings. But if you have to change bearings you'll need to inspect closely because usually it's not just the bearing that went bad- they almost universally take out the journal when they go. You can get a rough measure with a caliper. They make digital ones that are easy to read. A micrometer would be more accurate though. While it's generally not done if a crank was professionally remachined, it's entirely possible that one bearing is different than the rest. We do that on our ex-aircraft engines all the time due to the cost. Quote Link to comment
oldschool90 Posted June 8, 2011 Author Report Share Posted June 8, 2011 In fact you don't even have to remove the pistons/rods to change bearings. But if you have to change bearings you'll need to inspect closely because usually it's not just the bearing that went bad- they almost universally take out the journal when they go. Did this on my old honda when the oil pump wore out. Journal was bad -not trashed- just had scorch marks on it from getting hot. Just put new bearings on, drove it, and in less than ten miles, it was knocking again.. And in 20 (on the way to the JY, figures), the whole thing just died. (course, we didnt replace the oil pump either) So I guess I'll get a measurement with that micrometer when I get it apart. If I post the measurement, would you guys be able to help me figure out which size to get? Quote Link to comment
oldschool90 Posted June 8, 2011 Author Report Share Posted June 8, 2011 Shoot, my micrometer isnt big enough. Could I get a good enough measurement from a caliper? Quote Link to comment
oldschool90 Posted June 26, 2011 Author Report Share Posted June 26, 2011 I pulled my bearings today. Here's some oics: That number means 0.5 undersize, right? And a little off topic, I pulled the spark plugs out to turn the crank, and noticed that two of them didn't look like they were supposed to: The other two looked normal. Quote Link to comment
HRH Posted June 26, 2011 Report Share Posted June 26, 2011 Yeah that looks nasty. .5 should mean .50mm oversized on the bearing. That is .020 under. That bearing looks bad, down to the copper isn't good. Looks like the bearings I pulled out of the dead KA in the truck. If your crank needs more than an additional .010 off, I wouldn't use it, I'd find something better. You can get a decent set of calipers at NAPA, Schmucks, hell even harbor freight. They'll be plenty accurate provided you use them correctly. I'd measure all the journals on the crank, see if there's any difference between them. Hopefully not. Quote Link to comment
ggzilla Posted June 26, 2011 Report Share Posted June 26, 2011 Yes. 0.5 means 0.5 undersized. When refitting, buy some $5 plastigauge from RockAuto or Kragen/Grand/Oreilly and use it to confirm the correct bearing clearance. I need to change the rod bearings on my truck, but I'm not sure what size to get. I had to get another re-manufactured crankshaft about a year ago So the bearings in the engine which you just removed were not used with the new crankshaft? Then the markings on them mean nothing. The first plug looks a little oily, the 2nd looks old, like it hadn't been changed in years. Quote Link to comment
oldschool90 Posted June 26, 2011 Author Report Share Posted June 26, 2011 So the bearings in the engine which you just removed were not used with the new crankshaft? Then the markings on them mean nothing. I got a re-manufactured crankshaft, and those are the bearings that came with it. Quote Link to comment
yello620 Posted June 26, 2011 Report Share Posted June 26, 2011 How does the crank journal look where that bearing was removed? Pic? Quote Link to comment
oldschool90 Posted June 27, 2011 Author Report Share Posted June 27, 2011 How does the crank journal look where that bearing was removed? Pic? I took some 2000 grit sandpaper with oil on it to polish off the burn marks, and I'm happy about what I didn't find underneath. (grooves or any other wear marks) Quote Link to comment
yello620 Posted June 27, 2011 Report Share Posted June 27, 2011 Keep cleaning the crank, if it all looks that good, i wouldnt be afraid to put a set of bearings in it. Concerning though for some reason, why did these bearings go bad when the machined crank and bearings are only one year old? How many miles? Maybe time for a new oil pump too? Or better oil? You certainly are not going to be this lucky on saving a crank again next year. Need to get to the source of the problem. Quote Link to comment
oldschool90 Posted June 27, 2011 Author Report Share Posted June 27, 2011 Need to get to the source of the problem. That was actually my fault. I hooked up an oil pressure gauge and I had it hooked it up to run the oil light too. The oil gauge line kept getting air in it and i just got tired of bleeding it, so I left it. And the way I had the oil light sensor hooked up, I dont think it was getting a very good ground. So my dad takes it to work one day, and it runs out of oil halfway there because the gauge and light didn't work and we hadn't checked the oil level in a while. And just to double check, the bearings are .5mm undersized? I want to order them tonight. Quote Link to comment
HRH Posted June 27, 2011 Report Share Posted June 27, 2011 Make sure the parts guy knows what you want. The list bearings in thousandths AND mm. .5mm = .020" Quote Link to comment
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