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Con-rod nuts and bolts

jon s. blocker

jon s. blocker

GONE WEST
corpus christi, tx
I am putting together a Lyc 0290D for my J3/PA11. I bought the con rod nuts and bolts illustrated, and called for, in the Lyc parts catalog for the 0290 and 0235. It calls for part # 78027 (bolts), and # LW-12186 (nuts). I recieved them and assembled the lower end with no problems. My concern is that the bolts don't go together with the traditional nuts and cotter pins, they are plain nuts and don"t seem to even be self locking. I contacted ECI and they told me those are the same #s they list, and gave me a torque setting for them, which was a little tighter that what the overhaul manual called for. Everything went together well, but I'm just questioning the bolts and nuts. Any thoughts?
Thanks in advance,
Jon
 
Con -rod nuts and bolts

Wow, just took a pot of caldo over to my kids house, and there is already a reply, THANKS! I feel better about it now, but no, I did not lube the bolt. I have always been taught that lubing threads on a bolt will skew the torque factors so I torque them with dry threads. I always lightly lube the shank, but not the threads. Thank you again for the reply. Jon
 
I didn"t see anything in the overhaul manual that told me to wet torque the rod bolts. Dammit! Now I"m going to have to reread :(. My caldo is getting cold :). Thanks again.


Jon
 
I've never heard of lubing a bolt before torquing... but I'm willing to learn something new every day!
 
I reread the portion that pertains to installing the rods. It states to be sure and coat bearing inserts and the crankpin journal with a "liberal" amount of lubricating oil, but says nothing about lubing the bolts. Obviously it says to use everything new, which I have done. I assemble with a mixture of oil, Lucas stabilizer, and molylube, which I have done with my Porsche engines for years, with 0 failures. I think I have it right, :) Jon
 
Interesting read. They definately lube their bolts they insert into the rod. I don't know if we are compairing oranges to oranges, since they are not using nuts on their bolts, torquing the bolt to the rod as opposed to torquing a nut to a stationary bolt. That, I guess, is covered in their strech method, in which they still use lube. Believe me, I'm ready and willing to learn and accept good standard practices. I am probably operating on practices from the dark ages! Thank you again for your help and insight.
Jon
 
It has been a few years since I have had a Lycoming far enough apart to need to install rod bolts. As I recall, for a while there were rod bolts with a flat section on the tip. The nut was torqued and then a small "tubular" section of the nut was squeezed against the flats on the bolt with a set of pliers. This was the safety and could only be used once.
 
The overhaul manual calls out lubing the main crank gear bolt but I don't remember anything on the rod bolts. Good information in the Sacramento Sky Ranch Engineering Manual on rod bolts and nuts and why cotter pins are not needed. Friction and stretch if memory serves me correctly.
 
The small Continentals still use a castellated nut and cotter pin on the rod bolts, but the Lycomings use friction and stretch. I have not seen an overhaul manual that calls for lubing the rod bolts. Only preservative oil on the rod bearings upon assembly. I did run across one model of the angle valve IO-360 out of a Mooney 201 that I overhauled a few years ago where the Overhaul Manual did not give a torque value for the rod bolts. Instead, you were supposed to mic the rod bolts as you torqued them to measure the stretch of the rod bolts. Once it met the proper stretch it was considered to be properly torqued. In that case, it didn't matter whether you lubed the rod bolts or not. As best I recall, I did a couple of bolts that way and recorded the torque it took to get the appropriate stretch in the Overhaul Manual, then just verified with the mic after the rods were all in.

Sorry for the thread drift. Just thought it was an interesting tidbit of probably useless information. 8)

-CubBuilder
 
I have been through Navy classes (eons ago) on torquing electric primers for 5"-38 cal. propellant charges and we used to use something called "luting" (bees wax? and other smelly stuff??). It wasn't considered "torqued" unless the both internal and external threads were "go/no go" gauged, luting and a calibrated torque wrench were used. So I have always thought I knew everything there was to know about torquing and then this thread comes along. "Bolt stretch": that takes bad threads, slippery verses non slippery threads, uncalibrated wrenches etc. into account and is what you are actually looking for. I suppose bad metallurgy in either one of the parts is still a problem but traditional torquing will not show that up either. I wouldn't think it's usable in a blind hole but other than that: Neat!
 
The small Continental (65,85,90 and 0-200) overhaul manual in the table of limits says "Torque loads are listed for use with oil on threads, except for studs. Stud driving torques apply when the threads are coated with Alcoa thread lube if hole is blind, or with National Oil Seal compound if hole is through to a cavity subject to oil."
 
yes lubing bolts gives a more consistent torque....if you have a choice on lube go with arp suggested stuff...there isn't anybody that knows more about bolts. studs etc than them....there is typically a difference in torque settings for the same bolt lubed or non lubed....in the world of high performance engines the bolts are actually measured during torquing and torqued to a given length to insure proper tension......we put bots in tension because there is a certain elastic range in the material we are heading for...this provides the most strength for the material...........some of our fighters had an issue with breaking a bolt on front landing gear...material stretches as a percent and so the solution was to add spacers and a longer bolt of the same size so that the elastic range was physically larger and stayed together
 
The above posters are correct. The correct torque of Lycoming connecting rod bolts is critical. The bolt stretches which creates a tension that holds the nut. It is also the reason why you cannot reuse the bolt, ever. You should also achieve the final torque in one motion with the wrench rather than "stepping up" with several swings.
 
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