To torque or not to torque

[riobison]

Just installed 4 new Millennium Cyls to replace the ECI ones with the AD on the O320 in my RV9A

I have one mechanic telling me to torque those 2 through bolts to 65 ft pounds as marked in the foto even though I never touched them.

I have another one on the field that tells me to leave them alone.

The case only has 500 hrs or so on it.

Whose right?

In all honestly, I have a tendency to lean towards leaving them alone.

Thanks
Tim

 

[Jermechanic]

Torque them

I would torque the nuts. Hold the through bolts still and toque the nuts. The through bolts have oil sealing orings on them in the center of the cases so keeping the bolts still and undisturbed is the way I would go.

 

[Freemasm]

Just installed 4 new Millennium Cyls to replace the ECI ones with the AD on the O320 in my RV9A

I have one mechanic telling me to torque those 2 through bolts to 65 ft pounds as marked in the foto even though I never touched them.

I have another one on the field that tells me to leave them alone.

The case only has 500 hrs or so on it.

Whose right?

In all honestly, I have a tendency to lean towards leaving them alone.

Thanks
Tim

You are assuming they were torqued correctly to begin with. Even the best techs make mistakes. Put a calibrated wrench on them and “verify”. If you get movement (and trust the torque cal), expand your inspection scope.

Adding to the previous post; you should always be torquing the nut whenever possible to remove error.

 

[rv6n6r]

By the book

This: https://www.lycoming.com/sites/defa...%20Procedures%20for%20Thru-Studs%20and%20.pdf

My (inexpert) reading of this has us torquing only the cylinder nuts when it's only the cylinders being replaced. Regardless, don't take my (our) word for it, go by the overhaul manual and any service instructions. If it dinna say to do it, I wouldn't.
EDIT: Well, Freemasm has a point, so yeah it would depend on your confidence of what was done before. If it's the factory I'd definitely leave it, given that their method is far more reliable and accurate than we can hope to duplicate. And don't forget, proper torquing of through bolts is "wet" with a specific lubricant, and done in one smooth motion from torqued to the "click". So strictly speaking, you'd need to back them off first.

 

[riobison]

I'm not sure of it makes a difference or not but I only changed 1 cyl at a time.

The way I read this is that it's talking as if all of the jugs were removed at once then replaced.

Tim

 

[rmarshall234]

I would think Mike Busch has the best / most current advice regarding replacing cylinders, I would look there. Not sure I would want to “clamp” the crankshaft via the through bolts in the center w/o relieving clamp on the ends and following the torque sequence. It’s a good and important question, I wouldn’t proceed without an answer I was comfortable with. Good luck.

 

[riobison]

Yup. I agree

 

[lr172]

those are through studs and presumably you loosened the other side to replace the #1 cyl, so that should have been dealt with on the #1 installation. Never done a wide deck, but thought that the pro's put a torque wrench on each side of the through bolt and torque them at the same time to be sure the interference fit of the stud doesn't leave one side under torqued. I suspect many don't do this and likely no issue from not doing it, as I am not sure that is called out in the OH manual. I would also go back to the OH manual, as I recall those having a 50 ft lb torque, not 65, but could be remembering that wrong.

 

[riobison]

Yes, I only torqued up only what I removed. When I replaced # 1 cyl it made up to the 50 ft pds. No slippage other wise I probably would have looked for a problem and realized that I needed to back it up there.

And then why tell me and write down 65 ft pounds? Just adds to the confusion.

 

[BillL]

You are assuming they were torqued correctly to begin with. Even the best techs make mistakes. Put a calibrated wrench on them and “verify”. If you get movement (and trust the torque cal), expand your inspection scope.

Adding to the previous post; you should always be torquing the nut whenever possible to remove error.

Just putting a wrench on and pulling torque is not a valid method of checking tension. It should be marked, backed off 90 to 180 deg and then retorqued to see if it was low. This is standard in engine factories to perform QC checks where a dial type torque device is used to return to the marked clocking. All engine fasteners are well lubricated for torque so re-torque should do the same.

 

[riobison]

The through bolts on the front were at 45 pds, They were still at 50 on the other side. As well as the others were still at 50 where I had torqued them to.

I'm using a new SnapOn Torque wrench that has been verified as being in calibration.

Tim

 

[Freemasm]

Just putting a wrench on and pulling torque is not a valid method of checking tension. It should be marked, backed off 90 to 180 deg and then retorqued to see if it was low. This is standard in engine factories to perform QC checks where a dial type torque device is used to return to the marked clocking. All engine fasteners are well lubricated for torque so re-torque should do the same.

Guess I wasn't clear, Bill. The OP was debating whether or not to torque them. In theory, there was no reason but there could have been an installation quality issue. I didn't see any torque stripe in the pic. I suggested that if you got movement from applying the specified torque, more investigation would be prudent. The delta caused by static v dynamic friction (breakaway) alone would add perceived margin to the applied torque. I'll stand by what I said for what was intended. I've done similar in the past and been surprised more than once.

 

[avrojockey]

Just installed 4 new Millennium Cyls to replace the ECI ones with the AD on the O320 in my RV9A

I have one mechanic telling me to torque those 2 through bolts to 65 ft pounds as marked in the foto even though I never touched them.

I have another one on the field that tells me to leave them alone.

The case only has 500 hrs or so on it.

Whose right?

In all honestly, I have a tendency to lean towards leaving them alone.

Thanks
Tim

Doesn't hurt to torque both sides at same time like SI 1029 say's. Also...I believe it's 50 ft-lbs (600 in-lbs) not 65.

 

[riobison]

Yes, its 50 pds and that's what I went to. No idea on why he said 65.

 

[Majorpayne317641]

Yes, its 50 pds and that's what I went to. No idea on why he said 65.

Likely won’t get a good torque on it other than knowing either the bolt or the friction holding the bolt is 50ft lbs. The only way to know for sure, if you are wanting to touch these bolts… is from scratch by unbolting lubricating with the approved STP/straight oil assembly lube mix and two calibrated torque wrenches on either side. Technically even this will be not as accurate as if you used a brand new nut. There is a larger friction force on a new nut/stud combo that gradually reduces as you reuse the nut and stud. Eventually it tapers off to a certain friction. It has been studied and available for reading if you search, I don’t remember where I found it but it’s a mechanical engineering paper.