Rod bolts - a few questions and discussions Options

[ahdoman]

According to the experts it's imperative to replace the rod bolts when rebuilding. I've read the reason is because when they are torqued originally they stretch? Are they manufactured specifically to do that? If so, why wouldn't that make them weak? If reused why is that any different from reusing other bolts or parts under high torque? What's the science and logic behind this?

[ME733]

(IMG:style_emoticons/default/popcorn[1].gif) Rod Bolt stretch Guage....use....The guage is placed in such a way so as to measure the total stretch of the bolt at ANY TORQUE....USE the guage to measure the O.A.L. overall length of the rod bolt (WITH OUT THE NUT IN THE WAY BEFORE TORQUING)...this gives you the BASE LINE LENGTH of the specific rod bolt.(JUST for that specific rod bolt)....so you have got to take notes like real ENGINE builders do. ..so you get the O.A.L. of all (8) bolts individually. Install the rod bolts into the bottom cap...insuring that they are absolutely flush, seated....install top rod cap..tighten the new NUTS by hand easy, ..back and fourth, numerious times. YOU can feel the resistance , by hand , until the NUTS are seated on the upper rod cap., and the rod seperations..bottom and top cap is flush and secure...BUT NOT TORQUED. ...the ,,guage.. is made insuch a way that you can measure through the top rod cap NUT opening to the rod bolt itself , the bottom is the bottom of the rod bolt....Then ....with the specifications/ recommended for torque and rod stretch ..proceed to Torque the rod nuts/ bolts.(back and forth as you should do)...toward the rod nut torque specified....now What I specifically do is to keep shy of the FINAL torque recommendation by at least ..(2) two ft. lbs....I measure the rod bolt stretch..and compair it to the torque recommendation. if the bolt is stretched too much at this point.. that bolt must be replaced..even if its new, it has a defect somewhere. AND, I use a brass hammer, at this ..NON FINAL ..torqued stage. gently but firmly tap on the bottom of the rod bolts...to ensure they are completely seated. then walk off and give the assembly a opportunity to normalize itself. ( usually overnight). The FINAL 2 lbs of torque are applied and a final confermation check of the ROD bolt stretch is done. Each measurement is recorded., as you can reuse these bolts again if they maintain their diemensions... I made my own stretch guage,years and years ago..I use a Inch pound torque wrench.. to help ensure accuracy.( not a regular ft. # torque wrench)...(the CARRELLO rod bolt lubricants should be used for assembly...even if you use the A,R.P. bolts and nuts. (IMG:style_emoticons/default/popcorn[1].gif)