This Just In

[Roger Long]

Engine passed dock trials running an hour near maximum power that can be developed without moving through the water. Absolutely no sign of problems. Exhaust and crankcase breather liquid trap look great. Engine sounds better than it ever has.

Departing 1000 tomorrow and the mechanic is sure I can proceed as if it had never happened, other than the bill I'm about to go up and review and pay.

Film at Eleven

 

[kloudie1]

Congrats, Roger..

 

[CalebD]

Great news Roger. Somehow I thought a new head gasket might just do the trick.
I recently read an engine thread on another forum and MaineSail wrote that a load test on an engine should not be done while tied up to the dock for various reasons. Take a 1 hour motor locally under power just to be sure.
http://www.sailnet.com/forums/diesel-engine-forum/92290-universal-m25-losing-power.html
Still everything sounds very positive.
I hope it is so.

 

[navigator97]

Great to hear Roger. I'm glad that it worked out for you. Good luck and safe cruising. You have earned it. Keep us posted on you Spot as you travel. Thanks for all your posts.

Dick Carey S/V Puffin, K-15

 

[Roger Long]

I recently read an engine thread on another forum and MaineSail wrote that a load test on an engine should not be done while tied up to the dock for various reasons.

I just read that and it applies primarily to determining prop loading etc. All we needed to find out was whether the cooling passages stood up to close to maximum water pressure. Considering how fast the engine filled up, in about 3 miles of motoring, we should have seen something in the oil if there was a leak somewhere other than the head gasket.

It's pretty clear that the head had issues and improper repairs. I just remembered that I had some work done by the PO's mechanic when the boat was still out in Detroit when I bought it and everything he did I had to have redone. I can easily believe he just popped the head up on the studs, stuck some RTV in with a popsicle stick and tightened it up again.

BTW, I just got the bill. Much more than the initial estimate but much less than I expected after being right there watching all the work being done.

The hidden part of the bill is all the money I spent in the excellent restaurants just down the road.

 

[Scott T-Bird]

Roger, you will have to name your engine ...

Lazarus! You and your team of mechanics have raised it from the dead. Way to go! Maybe it was just "mostly dead" as Billy Crystal said in the "Princess Bride". Either way, congrats!

 

[Maine Sail]

Great news Roger. Somehow I thought a new head gasket might just do the trick.
I recently read an engine thread on another forum and MaineSail wrote that a load test on an engine should not be done while tied up to the dock for various reasons. Take a 1 hour motor locally under power just to be sure.
http://www.sailnet.com/forums/diesel-engine-forum/92290-universal-m25-losing-power.html
Still everything sounds very positive.
I hope it is so.

You can "load test" the engine at a dock just fine but what you can't do is test to see if the engine hits the RPM spec that they want to see with the prop. So if you had a Westerbeke that had a 3000 RPM rating and a prop that allowed you to hit 3000 RPM while moving through the water with clean bottom & prop you'd not achieve the same RPM tied to a dock.

 

[CalebD]

Brain de-obstipation on my part. Apologies.

On the bright side, now you could probably replace the head gasket on your own; not that you really want to.

Did they use a set of two (2) gaskets as recommended on my Atomic 4, or was it a single gasket? Just curious.

I think I speak for everyone here when I say we are glad that you can continue your trip back down south with confidence.

 

[patrickfarley]

Fantastic. I have been enjoying your posts for a long time. Glad you found a good mechanic.

 

[Neto Nomad]

woohoo!!!

 

[Benny17441]

I would still recommend that you retorque the head bolts much in advance of the 250 hours. This was a head gasket failure and not an incidental head gasket replacement. Those bolts should have settled enough after around 50 hours and prompt retorquing will insure that no uneven forces have a chance to develop. There will be no harm done, just a little work and you can do it again after 250 hours. Do not know how clean your mechanic was able to get the engine block threads and the bolts but oil residues and dirt specs can throw off the torque specifications.

 

[anchorclanker]

I second earlier re-torquing. On engines in which its easy to do, I almost always re-torque after the first hour or two, then again after 100 miles (10-20 hours), then at 1000 miles or 100 hours.

Re-torquing more than once or twice wont ever hurt anything, just make sure to back off each head nut or bolt 90 degrees or so before bringing it back up to full torque. Another suggestion is making sure the nut or bolt doesnt squeak or chatter as you torque it, it should be be quiet and smooth, allowing the full clamping force to be reached. We often have to oil or grease the threads and washers so that this can occur. Chattering means the threads are seizing and you will indicate full torque while not actually reaching it. This is in fact the reason many manufactures went to lower initial torque, then rotating 90 degrees, which would allow the chatter to have no real effect. Just to be clear though, you dont loosen all the bolts and then retorque them all, you do each one in turn, one at a time, following the prescribed pattern. You can even go around two or three times if you want, and will notice you gain a bit more each time on the bolts, showing that your squeezing the gasket down even further, which is ultimately the whole point. By doing it on a hot engine, the gasket will be more pliable and soggy, further allowing more compression of the gasket to take place.

 

[jibes138]

Bolts or screws have "running torques." This is the torque it takes to rotate the nut on the bolt before it comes in contact. The torque specification should be over the running torque. So if the nut takes say five foot pounds to run it down, and the torque spec is 100 foot pounds, then final torque on the wrench would be 105 foot pounds to get the right amount of clamping force. Most running torques are low if the threads are in good shape, but when you have nylon insert nuts for instance the running torque can be pretty high compared to the spec, so you need to consider that in the final torque.

 

[anchorclanker]

Bolts or screws have "running torques." This is the torque it takes to rotate the nut on the bolt before it comes in contact. The torque specification should be over the running torque. So if the nut takes say five foot pounds to run it down, and the torque spec is 100 foot pounds, then final torque on the wrench would be 105 foot pounds to get the right amount of clamping force. Most running torques are low if the threads are in good shape, but when you have nylon insert nuts for instance the running torque can be pretty high compared to the spec, so you need to consider that in the final torque.

I must take issue with this. In all cases everyone should always refer to service manual specs for torque. In cases where a manual is not available, standard torques values for typical fasteners can be used. In no case should additions ever be made to those torque amounts unless specifically mentioned. All bolt torque specs are given for the actual amount you read on the wrench unless expressly mentioned in the manual. Advising otherwise is simply poor advice and could lead to extreme damage and labor costs. Does running torque exist? Yes. But its always figured into the final torque specs given by the manufacturer.

While quite rare, head bolts are known to fail in tension under normal conditions. Overtorquing greatly increases the risk of failure and is not that rare, and often occurs during assembly. As bad as it is removing a broken fastener that failed from normal torque loads (they usually unscrew quite easily), you can have a real nightmare removing a broken bolt if the threads stretched. BTDT. If the bolt doesnt snap, you can rip the threads out of the block making it equally fun to repair. BTDT, too. Make a mistake converting NM or Kg m to Ft Lbs and youll see it first hand. And yes, BTDT too.

Always read the procedure, not just the spec. Most bolts are torqued dry, many internal engine bolts are not, but you need to read the specs because oil alters the reading. Oiling the threads and washers will allow much greater tension loads to be reached with lower torque. Head bolts are oiled only because they are trying to achieve equal clamping loads across the head. Which is another reason never to apply greater torque than specified.

Best is to simply follow the specs in the book and not try second guessing the engineering.

 

[jibes138]

The torque is calculated to result in a certain amount of stretch on the bolt. In some applications you measure the actual bolt extension versus the torque to ensure you have the proper clamping force. If the threads have contaminants and are in poor condition you can end up with a seriously undertorqued joint if you don't take into account the running torque. I hear you and understand what you are saying but in aerospace applications I've been involved with the running torque was considered in the final torque.

 

[jibes138]

This may help. Also type "should running torque be included in final torque of a bolt" in your browser and you will get lots of information about the subject.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960006814_1996106814.pdf

 

[leftbrainstuff]

I must take issue with this. In all cases everyone should always refer to service manual specs for torque. In cases where a manual is not available, standard torques values for typical fasteners can be used. In no case should additions ever be made to those torque amounts unless specifically mentioned. All bolt torque specs are given for the actual amount you read on the wrench unless expressly mentioned in the manual. Advising otherwise is simply poor advice and could lead to extreme damage and labor costs. Does running torque exist? Yes. But its always figured into the final torque specs given by the manufacturer.

While quite rare, head bolts are known to fail in tension under normal conditions. Overtorquing greatly increases the risk of failure and is not that rare, and often occurs during assembly. As bad as it is removing a broken fastener that failed from normal torque loads (they usually unscrew quite easily), you can have a real nightmare removing a broken bolt if the threads stretched. BTDT. If the bolt doesnt snap, you can rip the threads out of the block making it equally fun to repair. BTDT, too. Make a mistake converting NM or Kg m to Ft Lbs and youll see it first hand. And yes, BTDT too.

Always read the procedure, not just the spec. Most bolts are torqued dry, many internal engine bolts are not, but you need to read the specs because oil alters the reading. Oiling the threads and washers will allow much greater tension loads to be reached with lower torque. Head bolts are oiled only because they are trying to achieve equal clamping loads across the head. Which is another reason never to apply greater torque than specified.

Best is to simply follow the specs in the book and not try second guessing the engineering.

+1 to the above recommendations. A great deal of design and testing validation goes into the manufacturers' procedures and specs.

 

[anchorclanker]

This may help. Also type "should running torque be included in final torque of a bolt" in your browser and you will get lots of information about the subject.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960006814_1996106814.pdf

Okay. First of all, the file you link to deals with the engineering and testing used to calculate final torque of fasteners by determining the failure point in particular applications. That is where the specs put into service manuals are calculated. No one ever said running torque didnt exist. But service manuals, which come AFTER the egg heads have calculated out everything, already have that figured into the final spec. You dont add it again in service. In fact, if you read the bottom of page 3, and the top of page 4, it specifically deals with installation torque, and specifically states that you do not add beyond torque spec once that spec has been determined.

Guys, just do what the manual says and dont try second guessing it unless it appears in error, which they are sometimes (typos). If a manufacturer needs to make rocket science out of some procedure they will either explain how to do it or indicate the procedure is far too technical or requires tools that are unavailable to the general public and refer you to the dealer/manufacturer.

 

[jibes138]

AnchorClanker,

You sound like a mechanic talking with lots of real world experience. In the real world out there applications usually have tolerances so torque will be specified over a range to allow for inaccuracies reading the gauge, calibration of the gauge, etc. For bolts like head bolts the running torque will typically be very small so it can likely be ignored without any significant effect. In these situations I would expect good threads on both parts since they are in protected parts of the engine. If during installation a problem with the threads getting buggered up or cross threaded I recommend running a tap in the hole or a die on the bolt to chase the thread and make sure it is clean. When you are dealing with self locking nuts where threads are being cut in the nylon and the torque specification for small diameters is low, the running torque can be a very significant part of the total torque or even higher than the torque required for the final clamping force, in these cases it can not be ignored. Believe me I hear what you are saying but please be open to other positions also. I would not want a head undertightened on a diesel engine given the high compressions and potential for head gasket failure. A bolt is basically acting like a spring with the bolt stretching within the elastic region of the stress strain curve and applying a compressive force to the joint. Any designer will have allowances for fatigue and will not load a bolt up to the yield point of the material. Overtightening due to running torque is a highly unlikely scenario, but unless the threads are screwed up to start with it is unlikely it will be undertightened either. Still, please accept in good faith that there are other schools of thought out there, specifically in aerospace, that take a different position on this subject. Another example for you:

vtfast

Join Date: Jun 2007
Location: Portal, Georgia
Posts: 17

Running torque
All self locking nuts or nut plates have what you call a running torque. Once you get the bolt at least one thread into the self locking device you should see how much torque is applied to the bolt to make it turn. Add this torque to the final torque and you will end up with the correct finishing torque

Bolt running torque equals let's say 12 inch pounds,
Final torque equals let's say 32 inch pounds,
Final running torque will be 44 inch pounds.

Another example:

George - In the US Navy's Subsafe program (an extremely strict QA program for work on current submarines on any fastener involving the integer of the pressure hull - aka people tank). According to that program, the running torque of a nylock nut is recorder and added to the final torque applied to the joint. This insures that the final torque applied to a bolt is correct to produce the required tension on the joint. I doubt that this is really necessary to do on a fastener the size of a big end bolt. I have never checked it, but it would be my guess that the running torque of a 5/16" nylock nut would be less than 1 ftlb and not significant to the final torque. What I would seriously recommend is that a properly calibrated torque wrench when torquing rod bolts and wrist pin pinch bolts (on engines where they are used).


So I am not the only person in the world that is of the opinion it should be taken into consideration in critical assemblies.
Peace,
Dave