Quote:
Originally Posted by Assimilator1
Re your 1st point, err no, because very, very few people have come back reporting mains & rod bearings failing subsequently. Your logic fails there.
If the mains were failing at that point then the engine wouldn't last long at all after that, think in terms of a few hundred miles if you're lucky.
Main bearings aren't a bit more to do than rod bearings, as I've already told you they're a lot more.
About the rod knock, I thought so too, but some people (including at least 1 engine builder, Malek, photos here & report here) report just a light ticking or nothing at all (as in Maleks case).
If the crank gets irreparably damaged due to a rod bearing failure, then I know a new crank alone costs at least ~£3k (here in UK).
Also, Deansbimmer reported that when people here a knock it's usually already too late for the crank, IIRC he said he's managed to save 2 engines which had got to that stage.
Re strip down to look at mains when doing rod bearings, true most people don't so that. But as I said above, if it was as big a problem then their would have been plenty of people reporting that back too by now! |
Nope, incorrect. According to deansbimmer (you keep referencing) “where the mains failed and spun first, and the resulting lack of oil to the rods caused them to spin too. Since you can’t really hear a main failure there’s no indication of trouble until it takes out the rod bearings and they start knocking.” So unless everyone on the list has done an engine tear down, they likely will have no idea the mains have failed and have just assumed it was a rod bearing failure. The guy who posted that thread assumed it was his rod bearings only, but only discovered the mains were the culprit after the tear down.
https://www.m3post.com/forums/showthread.php?t=1565239
Never said they were a bit more work, I’m saying it makes no sense to do just the rod bearings when the main bearings will almost certainly show the same wear. Hence, I would change both if I was to do one.
Quote:
Originally Posted by Assimilator1
Nope, your logic is flawed here too, you're assuming the mains are under the same conditions as the rod bearings, they are not, any number of differences could explain why they fail (so far that we've seen in this not new problem) far less often than rod bearings. And, as I've said before, so far from what I've seen reported of failed engines, rod bearings are by far the more common cause. If I find that later in the list mains are more often reported as the cause of failure, I'll let you know (& others) know! (in that thread)  . |
The wear looks the same! So now you’re saying the failure is attributed to other “conditions”? You’re basically saying the wear isn’t the significant cause to the failure! If you’re saying that, then you’re throwing out your argument that rod bearing wear (the reason why you replace the rod bearings) is the reason for the failure! You’ve made absolutely no sense, I hope you can see how you’re contradicting yourself.
Again, the rod bearing failure reported could more than likely be a result of a main first bearing failure. Unless everyone on that list did a tear down to determine actual failure, you cannot say definitively that the failures were due to the rod bearings alone.
Quote:
Originally Posted by Assimilator1
Although the rod bearings are easier to do than the main bearings by far, that doesn't mean they are easy per se, seeing as it takes 8-10hrs+!!
If you could simply drop the sump off to get to the rod bearings (like you could on many older cars, some newer), then yes that would be easy!
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“Relatively” easy. So correct, rod bearings are easier to do than the main bearings by far.
Quote:
Originally Posted by Assimilator1
And again you're focusing on the <1% engine failure rate & ignoring the large number (but yes, not all) of rod bearings showing significant premature wear (even if you don't include the ones with marginal wear). I at some point am going to collate links & photos of rod bearings (from any engine) with normal wear with at least several 10s of thousands of miles on them for comparison.
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In your opinion, it shows significant premature wear.
You have been emphasizing that the wear on the bearings are your concern, yet you are saying other “conditions” are contributing to the failures…. So....
What about the “significant premature wear” on the main bearings????
Show main bearings where possible also. They always shows the same wear or worse.
Quote:
Originally Posted by Assimilator1
Anyway, I'm not trying to force you to do your rod bearings, I'm just trying to give you a clearer picture of the gamble you're taking, IMO you're being overly optimistic (and illogical) about it. Anyway, your choice & I don't want to expend anymore time on this discussion really  .
I'll keep my fingers crossed for ya. |
Nor am I forcing you to not do them (nor did you ever stand a chance of convincing me otherwise really lol).
Do them if they float your boat, but based off widely accepted figures and evidence at hand, it seems sensible not to do them.
Also, based off evidence that clearance isn't even a factor, and that M Sport intended the bearings with their design clearances, who know what problems may be introduced in the long term by putting in bearings with bigger clearances.
I’m pretty clear of the picture. Thanks for your concern, but I like my chances
