[SnapCoupe]

Originally Posted by lwgrenier

Right but I think the other guys want to know if the UOA is accurate so they can monitor bearing life with analysis rather than opening up the engine.

Agreed. If he pulls the bearings and they show wear, that can be used with an oil analysis to see if there is any correlation between the two. That way those who do an oil analysis can have a better idea of what their results are pointing to.

That being said, if OP recently changed the oil there isn't any reason to send off a sample.

[Welcome to NBA Jam]

Originally Posted by feuer

And what he is going to do if clearance isn't "correct" ? Is he going to have custom made bearings to get the clearance spot on? Or put electrical tape between rod and bearing to making tighter? Or sand it down to make it looser? Most defiantly not. He is removing bearing size X and replacing it with another bearing of identical size X. So why plastiqauge? Is absolutely purposeless for what he is doing as he wont be able to correct the issue without removing the crank, machining the crank, getting larger bearings and then plastigauge to check if clearances are ok. This is main reason why shops aren't doing it either. Isn't because they are careless.

For the same reason you check the gap on your spark plugs. Tolerances aren't always in-spec, and the right part isn't always in the right box. If it's out of spec and you don't have the means to adjust it, you go back and get a replacement part that is correct and test again. Incorrect bearing clearances can be catastrophically bad.

It's not my car and he can do what he wants. I find it to be a weird low-effort step to skip considering the bearings are already going to be taken off.

[feuer]

Originally Posted by Welcome to NBA Jam

For the same reason you check the gap on your spark plugs. Tolerances aren't always in-spec, and the right part isn't always in the right box. If it's out of spec and you don't have the means to adjust it, you go back and get a replacement part that is correct and test again. Incorrect bearing clearances can be catastrophically bad.

It's not my car and he can do what he wants. I find it to be a weird low-effort step to skip considering the bearings are already going to be taken off.

...ok and clearance isn't ok due to the crank. What is he going to do? Replace it? Also, who check the gap on spark plugs? Unless tech look for specific gap needed the spark plug will be installed as is.

[TripleD2047]

Originally Posted by feuer

...ok and clearance isn't ok due to the crank. What is he going to do? Replace it? Also, who check the gap on spark plugs? Unless tech look for specific gap needed the spark plug will be installed as is.

Not all spark plugs are pre-gapped. The clearance is to ensure correct firing and I use plugs to be manually set.

[feuer]

Originally Posted by TripleD2047

Not all spark plugs are pre-gapped. The clearance is to ensure correct firing and I use plugs to be manually set.

I completely understand that, the main deference is: gap on spark plug can be easily corrected and fatty335 won't be able to correct anything if clearance isn't correct after determining with plastigauge. I'm not nitpicking, just maybe use different example. I can't think of one.

[hassmaschine]

Originally Posted by feuer

...ok and clearance isn't ok due to the crank. What is he going to do? Replace it? Also, who check the gap on spark plugs? Unless tech look for specific gap needed the spark plug will be installed as is.

Get different bearings, of course. Double check the installation. Re-use the old ones if they're fine. If it's out of tolerance with new bearings and he uses them anyway, engine damage is almost certain (or at least reduced life). Anything other than "hope for the best" would be better than not checking.

Don't pretend all things are manufactured perfectly. I know all about BMW bearing shell color codes - and sometimes, they are just wrong. This has come up several times with people rebuilding engines at home (or with a shop), the bearings were either the wrong ones or were out of tolerance or the crank actually wasn't the "standard" yellow/red code. Easily detected with the use of a cheap $10 kit.

Using a plastigage is so easy and cheap, it would be extremely foolish not to do it, given the possible repercussions - never mind the fact that it's unlikely the bearings in this engine need replaced to start with, he's opening a can of worms.

[feuer]

hassmaschine very convincing argument with relevant points!

[hassmaschine]

And honestly, there's a 99.9% chance that the new bearing shells will have perfect tolerance. When I built my M20, I used an unknown-mileage crank from a junkyard engine. All I did was clean it up, use stock red/yellow shells, and checked it with a plastigage - and of course, the tolerances were perfect, even though that crank probably had at least 150k miles on it. That was over 100,000 miles ago...

You just don't want to be that 0.1%.

I don't know if the kits are different now, but 1 kit is probably enough to build several engines (I still have mine somewhere from 12 years ago). so sell it to your buddies when you're done?

[fatty335]

Ok, in the spirit of furthering our collective knowledge (and not doing irreparable damage to my motor, according to some), I'll concede. I've ordered some PG-1 Plastigage and will measure to ensure the new bearings are between the Min (0.00098) and Max (0.00280) clearance for the N55.

Also, I have encountered my first area of real concern while researching the correct OE rod bolt torque procedure - arguably the most important torque setting of this whole job. My Bentley does not cover it, newTIS is calling for a joining torque of 20Nm, then angle of rotation of 70 degrees, then 70 degrees (70 degrees twice? very confusing), BMWworkshop-manuals for the N54 (same rod bolts) calls for 20Nm, then 70 degrees, while some on other sites have advocated for 20Nm and 140 degrees of rotation. Can anyone with a bmwTIS login or some other authoritative source of information weigh in? This is the one torque setting I can't afford to get wrong!

[feuer]

The Bentley manual I have doesn't cover the oil pan but rod bearing are in there. Says 20nm and 70' which is what I have been doing. I go 10nm first, then 20nm, finishing with 70'. TIS online says the same. 70' + 70' I have seen only screen shots from people posting on the forums. 140' haven't seen at all.

[fatty335]

https://www.newtis.info/tisv2/a/en/e...rings/8GvWX6fP

The "70 degrees" listed twice is what is confusing me at the moment.

[TheMidnightNarwhal]

Originally Posted by hassmaschine

Get different bearings, of course. Double check the installation. Re-use the old ones if they're fine. If it's out of tolerance with new bearings and he uses them anyway, engine damage is almost certain (or at least reduced life). Anything other than "hope for the best" would be better than not checking.

Don't pretend all things are manufactured perfectly. I know all about BMW bearing shell color codes - and sometimes, they are just wrong. This has come up several times with people rebuilding engines at home (or with a shop), the bearings were either the wrong ones or were out of tolerance or the crank actually wasn't the "standard" yellow/red code. Easily detected with the use of a cheap $10 kit.

Using a plastigage is so easy and cheap, it would be extremely foolish not to do it, given the possible repercussions - never mind the fact that it's unlikely the bearings in this engine need replaced to start with, he's opening a can of worms.

Exactly. I always thought the reason clearance is checked is just to get a double check and be 100% the bearings are good sized because as you say if a bearing isn't in spec it's not good right.

[feuer]

Originally Posted by fatty335

https://www.newtis.info/tisv2/a/en/e...rings/8GvWX6fP

The "70 degrees" listed twice is what is confusing me at the moment.

Bolts aren't m9. They are m10. Also say oil the bolts. If you oil the bolts it will require diferent tightening procedure.

[fatty335]

Originally Posted by feuer

Bolts aren't m9. They are m10. Also say oil the bolts. If you oil the bolts it will require diferent tightening procedure.

Now I'm really confused, feuer - the rod bolts I ordered for the 2011 N55 are M9x47mm. Also, every source I have found begins with, "clean and oil the bolts." Are you providing info for something other than the N55?

[feuer]

Originally Posted by fatty335

Now I'm really confused, feuer - the rod bolts I ordered for the 2011 N55 are M9x47mm. Also, every source I have found begins with, "clean and oil the bolts." Are you providing info for something other than the N55?

Yeah, I double checked. They are m9. Sorry for the confusion. But if you oil the bolts you will need to torque them more.

[TZANIDO777]

Would a rod bolt stretch gauge be a more accurate way to measure the torque being applied to the rod bolts during install?

[hassmaschine]

They are torque to yield, I don't think measuring stretch is going to be helpful.

The procedure in the TIS is the one I would follow, and be particular as to whether they say oil the bolts or not.

TTY is actually very forgiving. Even if you were 10 degrees off (+/-) it would still work fine. But of course with a torque angle gauge you should be closer than that..

I always just made my own from an old CD, marked the angles with a sharpie and lined it up with my breaker bar (don't use a torque wrench for TTY bolts). Works every time.

[bbnks2]

Originally Posted by TZANIDO777

Would a rod bolt stretch gauge be a more accurate way to measure the torque being applied to the rod bolts during install?

BMW does not publish stretch measurements to go off of, but yes, that is usually more accurate than relying on a predetermined angle. My aftermarket rods supplied the proper stretch, but, they also supplied an alternative means of torque+angle.

https://www.newtis.info/tisv2/a/en/e...rings/8GvWX6fP

Proper torque specs are 20nm then 70* + another 70* (replace, wash, and oil). I am sure there is a special oil BMW wants you to coat them in that you should be bale to find on TIS. Friction is super important to get the correct stretch.

TTY and stretch used interchangeably by BMW. There are technically are very few, if any, bolts in a BMW motor that are "torqued" to yield. Almost every bolt is stretch to yield using angles (5nm + 30* 15nm + 45*, 70nm + 360* etc...) and are 1-time use.

[TZANIDO777]

Originally Posted by bbnks2

BMW does not publish stretch measurements to go off of, but yes, that is usually more accurate than relying on a predetermined angle. My aftermarket rods supplied the proper stretch, but, they also supplied an alternative means of torque+angle.

https://www.newtis.info/tisv2/a/en/e...arings/5tRriB5

Proper torque specs are 20nm then 60* + another 60* (replace, wash, and oil). I am sure there is a special oil BMW wants you to coat them in that you should be bale to find on TIS. Friction is super important to get the correct stretch.

TTY and stretch used interchangeably by BMW. There are technically are very few, if any, bolts in a BMW motor that are "torqued" to yield. Almost every bolt is stretch to yield using angles (5nm + 30* 15nm + 45*, 70nm + 360* etc...) and are 1-time use.

Got it, I figured as much since I have been going through TIS and also didn't see any stretch measurements.

Does anyone like ARP offer rod bolts for the N55 engine?

[hassmaschine]

Originally Posted by bbnks2

TTY and stretch used interchangeably by BMW. There are technically are very few, if any, bolts in a BMW motor that are "torqued" to yield. Almost every bolt is stretch to yield using angles (5nm + 30* 15nm + 45*, 70nm + 360* etc...) and are 1-time use.

That's because they are the same thing. While you don't use a torque necessarily, the 'yielding' of a bolt specifically means it stretches. Saying Stretch to Yield would be redundant..

Technically, yes, a stretch gauge would be more accurate - but given the top of a yield curve for steel is flat (as long as you don't reach the ultimate strength of the material), it's not going to make any difference for the purpose vs sticking to the BMW specified torque angle. Also without a published stretch value, it wouldn't be useful anyway.

[bbnks2]

Originally Posted by hassmaschine

That's because they are the same thing. While you don't use a torque necessarily, the 'yielding' of a bolt specifically means it stretches. Saying Stretch to Yield would be redundant..

Technically, yes, a stretch gauge would be more accurate - but given the top of a yield curve for steel is flat (as long as you don't reach the ultimate strength of the material), it's not going to make any difference for the purpose vs sticking to the BMW specified torque angle.

I was replying to your statement that measuring stretch would not be helpful because they are torque to yield. I assumed you were trying to say that they aren't stretch bolts.

[hassmaschine]

oh, no of course I think they are stretch bolts. TTY implies that they will stretch once you reach the 'yield' point of the bolt.