Lycoming Connecting Rods..

[jetdoc31]

I have found a NOS set of Lycoming rods PN# 5104-61477 stating they are for a O-290. My O-290 manual calls out 78030-S as the correct part. Is the 5104-61477 a old P/N? Couldnt find much on the way searching online...Thx

[pmanton]

Sky Ranch engineering manual states that they are superseded by 61474-S which in turn was superseded by other numbers

Paul
N1431A
2AZ1

[mmoyle]

Question for the engine builders... Connecting rod orientation. The manual says number side down...toward the pan. When you don't have numbers? What I can't find is bearing tang up or down....or on which side when all rods are orientated the same direction.


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[longpacer]

On my O-320 rods, the bearing notch on the connecting rod piece (not the cap piece) is on the same side as the cylinder number stamp.

[mmoyle]

Ok. That answers my question. Thank you. Ill number stamp after assembly.

[Steve Pierce]

Where did you get connecting rods with no numbers? Never seen any without.


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[mmoyle]

Need to look at the tags. Think it was the same outfit that re ground the cam and lifter bodies. They were reman. 2 at 799 grams. 1 at 805.2 grams. The third at 805.7 grams. Piston weights/opposing assemblies will be the same.

[mmoyle]

Assembled...numbered one through four...http://tapatalk.imageshack.com/v2/14/12/25/9f65993e84310858e7e091c4de363490.jpg


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[Steve Pierce]

So how did you decide which side to stamp?


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[mmoyle]

Numbers on the bearing tab side.


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[gliderman]

numbers should be away from the camshaft.....

[mmoyle]

numbers should be away from the camshaft.....

Thanks...found that bit in the overhaul manual. What I couldn't recall was which way the bearing tabs faced. Then perhaps having concentric rods? The over thinking it kicked in...again...sometimes it's a big stumbling block to getting something done because I'm familiar with having backwards progress. Of all the engines I've rebuilt...non-aviation. I've missed the gear timing on one...it was a 4-53 Detroit. I'd done perhaps a hundred of 53 series engines...and I screwed up. Recently I overhauled a 3304 cat. Couldn't get it to start. Tore the front of the engine down...got that right. Put it back together with new gaskets and seal. Removed number one injector check the piston position with the pump timing. Turned out to be a weak injector pump. Then even more recently a C4.4 timing issue. Couldn't time the damn pump for the engine .....felt pretty dumb over that one...turned out it wasn't my screw up....wrong pump from Cat and the wrong timing tools. Got the right pump...used my dial indicators to old school time the engine....restored power to the community......guess I've become timing shy!


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[Frank Green]

OK so I'm putting my O320 back together and I've got my new 78027 rod bolts and 12186 nuts. I've read SI 1458G several times and I can't get my head to accept no safety or locking of the rod nuts. For torquing it specs food grade anti-seize? My aviation instincts want me to saftie everything and what seems to me to be the most important nuts in the engine, nothing? I don't understand what Lycoming is thinking. The crush nuts made sense. Didn't effect the torque value and were not position related like a castle nut. Can any body explain this or am I going to think about those nuts every time I get in the plane?

[bluejeepdad]

It's friction in the threads and under the nut that keeps it from turning and loosening. In heavily loaded fasteners like rod bolts you need to put the bolt in enough tension to eliminate fatigue failures which is what the torque spec does. With that amount of tension you also get a lot of friction that prevents rotation of the nut. The only way the nut will turn is if the bolt looses tension for some other reason. But once the bolt looses tension (for whatever reason) the rod will fail in a hurry anyway. Secondary locking devices don't really change the outcome in this case. The most important thing is to know that the torque wrench is accurate.

Tim

[Frank Green]

Sounds OK for John Deere but I still don't find it to be a aviation standard. It is what Lycoming says, I just don't get a warm funny feeling about it.

[Jim]

Hi Frank,

Take a quick look over the whole engine and you'll find dozens of non safe tied nuts. For example, the case halves, and quite a few cylinder hold downs aren't either. It's kind of like when people mention attaching steel to aluminum causing corrosion. Our engines are made with a mixture of those metals without terminal corrosion problems developing. These things have been holding their own for sixty plus years.

[Frank Green]

For 60 plus years they used crush nuts, I just don't get the change. It's just contrary to every aeronautical philosophy. After 23 years working on AF jets I want to safety wire the valve stem caps.

[mmoyle]

Frank....felt the same when I did my engine.... wanted those special roll pins to lock the nuts....just like the pins I removed. Thing is these engines don't see nearly the same pressures and vibration as compression ignition engines...diesel. Lost count of overhauls I did on a variety of diesels that came over on the Arc with Noah. Many of which used safety wires or cotter pins on the rod nuts. Reassembly with new rod bolts and non castle nuts. Torqued to spec and measured the bolt length to insure proper tension. Never ever had a come back...cept this one time after band camp.....I cut the blower seals on a 6V92TA. Bout the only engine/s I can recall using safety wire on the rod nut were on 590 and 1090 Hall-Scotts...those rods were shimmed to gain the proper bearing clearance. Shim stock is soft...so safety wire is a must.


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[gliderman]

Frank
Same basic setup on TI0-540 engines (Navajo)
Whole lot more "oomph" there
Not to worry about the bolts
But as stated earlier: get your torque wrench calibrated !!!!
Hope this helps
Shane-o

[Steve Pierce]

Frank, I would suggest you get the Sacramento Sky Ranch Engine Manual. Excellent read and reference. They talk about stretch and tension in rod bolt applications. I just think about it working on those souped up aerobatic engines with way more forces than our engines will ever see.