Aligning of con rods

[german4inline]

Guys,
I´m currently thinking about how to align rods, either custons or stock rods. 30 years ago i was involved in producing special forged rods for a german tuner, and after the machining ( milling a.s.o.) we noticed that the rods were a bit warped once the tensions were getting free. The forgings were out of a process of an OEM Producer and we didn´t any special heat treatment. So we had to realign the rods by using a common gauge for checking the runout and we bent them properly back to get them straight. But anyway i noticed with some of them and some rebuilt engines after dyno runs that the rod were snapping back to the old run-out ( at least they didn´t stay perfect). Now I have made a set of Special billet rods for my small Renault engine,they are really perfect machined with very tight tolerances, but after quench and tempering, the have a small run out of 0,12 mm (about 1/20th of an Inch). The material is 4340 billet steel, they are I-Profile ( ist a N/A engine, maybe 9000 rpm, but only 1800 cm³ displacement). I never did realign billet rods in the past and I´m not sure if they will snap back after realigning. The upper bosses (of the pin hole) are not yet finish machined and some of you would advice to leave the rods like they are and finish the pin holes so that the rods holes are parallel. Thats right indeed, but the lower and upper bosses are offset and if i just rework the rods to make them parallel and straight, the thrust faces of the upper holes are looking like **** because the milled thrust face will getting bigger whilst milling them. The rods were not really cheap and i want them to look as made by a professional even i don´t see them inside the engine....Is it a common Problem with billet custom rods to have to realign them oder at least check them for alignment ( and rework if required)?
And if so, how easy it is to get it done and do they snap back or do they stay?

[strokersix]

I think you need to incorporate some stress relief in your process. Before machining if possible.

May be as simple as cooking them in the oven at 500F for a couple hours. Others may have more specific advice.

[Kevin Johnson]

Udo,

You should ask Speedtalk member "Stef" about the rods.

https://www.speed-talk.com/forum/memberlist.p ... ile&u=1965

https://www.facebook.com/TTVRacing

[german4inline]

I think you need to incorporate some stress relief in your process. Before machining if possible.

May be as simple as cooking them in the oven at 500F for a couple hours. Others may have more specific advice.

I even stress relieved them before quench and tempering just to avoid warping as far as possible. I think that worked very good, the threads were very nice to screw in and there was not the smallest run out of them. I´m pretty sure that the warping is as small as possible, but anyway existing. the omly way to avoid this small amount is to machine the rods everywhere with a small allowance and after heat treatment they have to be finished with Carbide metal Tools, what is very expensive due to the big expense. And however, also with this methode you can´t be sure to avoid any warping. As soon as you remove metal, the tension condition alters.

[german4inline]

Guys, got the rods realigned, with a self-made device in the vice, with some feeling gotten by try and error, with half a thou run-out.
Thanks anyway !

[Kevin Johnson]

I hope you plan on cycling the rods in a small kitchen oven to 100 C and letting them cool to room temperature several times. Then recheck your alignment. Remember your experiences from thirty years ago, richtig?