So, this is something I’ve been thinking about recently and wanted to open it up to more discussion and to hear about your experiences. We all build engines. Tear them down after failure and find root cause. My question is when are you guys seeing factory bearing failures? Mainly discussing main and rod bearing failures.
Factory Bearings ?
- Thread starter KyleC4
- Start date
Not a failure per se, but when I tore mine down years ago the crank bearings all looked good, but the rod bearings all had excess wear on the top half, including a couple into the copper (IIRC, those were the rods that bent). The thrust bearing showed some wear but not overly bad. Oil pressure was still excellent (+80 cold, +40 hot, +25 idle) so the wear didnt seem to hurt anything. That was 156,000 miles, drag racing, and sled pulling.
Only time I've seen main bearing failure(spun) was high mileage and low maintenance. Oil was tar, couldn't scrub it off your hands for a week. Sounded awful, assumed it was a broken crank when he pulled in.
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The only thing i can say about stock bearings is they are soft so its easier to beat them up under a high HP engine. usually stock rod trucks have something else go before the bearings are beaten out of it but id be curious what some of these 700-800hp stock engine trucks are seeing for bearing wear.
when i looked at the clevite H's i pulled out of my first built engine (had somewhere in the 60-70k miles on it), they had some wear but looked awesome. that engine saw 600hp daily, towed on the same HP and ate lots of transmission parts from towing that way lol. the block just couldnt handle a 7th headstud torque at 150ft lbs....
when i looked at the clevite H's i pulled out of my first built engine (had somewhere in the 60-70k miles on it), they had some wear but looked awesome. that engine saw 600hp daily, towed on the same HP and ate lots of transmission parts from towing that way lol. the block just couldnt handle a 7th headstud torque at 150ft lbs....
That has been my curiosity. What would factory bearings look like in a 700-800hp truck that’s daily driven. And also setup for each scenario to make that power level. Wether being compounds or large single, fueling setup, and vehicle usage. But, also all other factors like oil temp, oil type/grade any variable to rule out that didn’t cause a bearing to fail prematurely.
Tom, your findings would have been interesting to take a dial bore gauge to and see if the bearings were out of round in the rod from the wear. Do you remember if the rod journal on the crank showed anything that would require maybe a polish….? I’m assuming nothing further since you had great oil pressure still prior to tear down.
But simply, my wonder is how long could the factory bearings last in that HP range. I feel like that’s a number that’s not overkill, over reaching, what ever word I’m looking for, to stress a bearing and see it’s durability. Hopefully a couple more people can chime in with their findings or thoughts
Tom, your findings would have been interesting to take a dial bore gauge to and see if the bearings were out of round in the rod from the wear. Do you remember if the rod journal on the crank showed anything that would require maybe a polish….? I’m assuming nothing further since you had great oil pressure still prior to tear down.
But simply, my wonder is how long could the factory bearings last in that HP range. I feel like that’s a number that’s not overkill, over reaching, what ever word I’m looking for, to stress a bearing and see it’s durability. Hopefully a couple more people can chime in with their findings or thoughts
Crank was fine, as I remember. All the stress had been taken by the rods and the rod bearings, in my estimation. BTW, that was at ~580rwhp.
The truck was not ran easy300 passes on nitrous I think I’d expect to be tearing down a motor at least for an inspection. But that’s really good. It’s in line with what I hear from these LS engines out there that guys are running factory bearings.
So you were making over 600 at the crank then Tom. And for you a rod(s) went before any bearing actually did at 160k.
James, you had 60-70k on H bearings….. what is the expected life out of those ? I thought Mahle had said 100k but that could be totally misinformation.
So you were making over 600 at the crank then Tom. And for you a rod(s) went before any bearing actually did at 160k.
James, you had 60-70k on H bearings….. what is the expected life out of those ? I thought Mahle had said 100k but that could be totally misinformation.
i couldnt say what the expected life would be. if they give one, its going to be very specific on power rating, use, rpm and so on. At the time i built the first engine, i had a wishful goal of 100k out of it doing what i did and that seemed like a stretch. I did make it over the min 50k miles i wanted though lmao.
I see no reason they couldnt go 100k miles at 6-800hp on a daily driven rig assuming oil never gets contaminated or other variables dont lead to hurting them. i would run them in an engine over stock bearings if i had the choice (assuming proper clearance is done and machining).
Yes, easily over 600chp. Iirc, it was 2 or 3 rods that were bent, one was pretty bad. Truck still ran fine, but smoked harder on cold startup. Like I said, bearings were worn but did not affect engine perf before the rebuild.
What’s the race series bearings? I have over 125k on those. Truck still runs lol
No idea, I think they are all the same based on the info I know. There is H and HX. HX is just slightly larger clearances, no other difference
Ok so now with clearances. What could happen if you were to take main and rods, machine them to make an extra .0005in oil clearance, change to a 20w50 with good zinc content, change oil pump pressure and volume, keep oil and coolant temps in check, could you increase your use of a factory bearing ? Will adding the extra oil film thickness help a factory bearing last longer in a 600-800 range?
At the end of the day, the bearings are soft. No pressure or oil can fix it. Cylinder pressure will eventually deform the bearing and cause accelerated wear.
I think that in our relatively slow rpm v8 application, the thicker film is better. In higher rpm applications, and in inline engines, the tighter clearance and thinner oil is free HP. Oil temp and upstream heat loading seems to have more effect than clearances on bearing life in our engines and in the v6 diesels I've had apart so far.