I am putting together the parts necessary to rebuild my O-320-A2A. I bought connecting rod bolts PN 78027 and nuts 74646 based on the thought that my connecting rods where PN 78030. I bought the 74646 nuts based on the narrow deck ?A2A parts list.
My first concern is that the nut 74646 is unlike most connecting rod nuts I?ve seen. It has about a ? in lip while the others I?ve seen have about a 1/16in lip. I put the two side by side below. You can somewhat makeout that the nut lips are different lengths.
From what I can discern from Lycoming SI-1106D that extra ?lip? is there because the 74646 nut is an ?older? style crimp bolt. It was later replaced with LW-12186 since Lycoming found crimping the bolt did not significantly decrease the likelihood of connecting rod failure.
My questions:
1)Is there any special procedure for crimping the connecting rod bolts or should I not worry about crimping them altogether?
2)How can I verify I indeed have connecting rods 78030? I was told this by AEA in Dallas but I cannot seem to make sense of the markings on the connecting rod.
Any help would be appreciated!!
My first concern is that the nut 74646 is unlike most connecting rod nuts I?ve seen. It has about a ? in lip while the others I?ve seen have about a 1/16in lip. I put the two side by side below. You can somewhat makeout that the nut lips are different lengths.
From what I can discern from Lycoming SI-1106D that extra ?lip? is there because the 74646 nut is an ?older? style crimp bolt. It was later replaced with LW-12186 since Lycoming found crimping the bolt did not significantly decrease the likelihood of connecting rod failure.
My questions:
1)Is there any special procedure for crimping the connecting rod bolts or should I not worry about crimping them altogether?
2)How can I verify I indeed have connecting rods 78030? I was told this by AEA in Dallas but I cannot seem to make sense of the markings on the connecting rod.
Any help would be appreciated!!