To Loctie or not to Loctie, that is the dilemma

[snowman]

Wayne,

I see no reason for the locktite to lengthen the life of an engine, even with a latent failure mode. People who have made it their LIVING to study fasteners, that means they have devoted their LIVES to studing fasteners ( I for one do not know how someone could do this, but they do) do not agree. I have learned, that you do not argue with people who devote their lives to the study of a subject, they DO INDEED KNOW MORE than the average mortal. One of the keys to overall success is to listen to the learned ones, and then translate it to meaningfull practice. There are two types out there The practical hands on types, the ones you used to write your book, who have the most usefull information, for immediate use, but also listen to the other group, the ones on the mountain top for where things are going in the future. They really do know what they are talking about and the future gurus of the present will be spouting their wisdom when the time comes.

In other words the geeks do know a bit of what they are talking about, it only takes a bit of time for it to sink in.

[1fastredsc]

I've got another question, while locktite will prevent the nut from backing out of the rodbolt, does that really matter if it's streched. In other words, if the rod bolt has stretched enough to be relieved of it's clamping pressure, that means there might be a minute gap that has developed between the bottom and top half of the connecting rod. If this occurs, would'nt the shock of the rod constently beating on it's bottom end like a jackhammer be more than enough to break the rod bolts. (and look something like the picture posted by Mr. garibaldi)

[1fastredsc]

Originally posted by Wayne at Pelican Parts
The failures that have been seen have been detected in 3.2 and 3.6 engines, which have rev-limiters. Technically, I guess you may say that the rev-limiter was set too high for the structural limits of the rod bolt?

-Wayne

OK, i think i read your first post wrong then, when you said over reved i assumed you meant over the rev limiter.

[1fastredsc]

Oh, and Jim Sims, what do you mean by "(five cycles of tightening and loosening to reach a constant and stable thread friction)" as posted in that thread that you linked. I've never heard of this and my father is using arp headstuds in his 951. I'd like to know so that i can make sure that the head is torqued properly.

[Wayne 962]

Originally posted by 1fastredsc
I've got another question, while locktite will prevent the nut from backing out of the rodbolt, does that really matter if it's streched. In other words, if the rod bolt has stretched enough to be relieved of it's clamping pressure, that means there might be a minute gap that has developed between the bottom and top half of the connecting rod. If this occurs, would'nt the shock of the rod constently beating on it's bottom end like a jackhammer be more than enough to break the rod bolts. (and look something like the picture posted by Mr. garibaldi)

Yes, at this point, the engine would probably fail. My overall point is that it is my estimate that the time and steps that it would take to get to this point would be lengthened by the use of Loctite.

-Wayne

[Jim Sims]

"five cycles of tightening and loosening to reach a constant and stable thread friction" If one is using the torque wrench method with the higher strength aftermarket bolts (not the torque to yield OEM bolts) this process is used to smooth out the threads and evenly distribute lubricant amongst the threads. Such a process slightly reduces the variability of thread friction and hence the scatter of achieved bolt tension and joint clamping force. One of the aftermarket vendors (I can't recall if it is Raceware or ARP) recommends this process if a torque wrench is to be used. The stretch measurement method is the preferred approach although it too has problems. One of which is the variable geometry of the bolt, nut and parts in the grip of the joint. The cross-section of a practical bolt is far from constant, the distribution of load amongst the threads in the area of nut is unknown plus there is is bending in addition to tension. These uncertainties require prudent design with adequate margins or if one can't (sometimes one is forced to go to the bleeding edge) then the chance of failure should be factored into the operational considerations of the device. Cheers, Jim