If posted this a half dozen times, maybe more. I’ll post it again because it’s exactly what I’ve been saying.
Tom Leib who owns Scat is 100% against stretching rod bolts. At one time I posted the link to the webinar he gave where he covered it.
I quit stretching bolts a long time ago because I learned the hard way what Leib was saying.
No matter how good the bolt is, they stretch at different torque values. When you do that, you pull the hole out of round. Yes, you can size them and make them round again, but…and this is a big BUT under heat and load the big end will distort to the unequal load on the bolts.
I found this out because I was meticulously measuring, recording and stretching every rod bolt I had. And anyone else that I was building junk for. And, I saw a trend.
That trend was running steel rods the bearings may look a bit wonky SOMETIMES. But you stretch a rod bolt in an aluminum rod and the rod bearings will look like **** in short order.
Most of that stuff was 8k plus but you could see it happening plain as day. So I called Childs & Albert (I ran those rods for a bit) and Bill Miller and several other aluminum rod manufacturers and only C&A said to stop stretching the bolts.
Then I decided I better call on some people smarter than me who were building big power aluminum rod **** and every single one said stop stretching the bolts and torque them so the load at the parting line is as close as you can get.
And all the wonky looking rod bearing crap stopped. Even the steel rod stuff.
I will not stretch a rod bolt. It’s the only bolt that even possible to stretch in an engine. I suspect someone decided since they could measure it it must be done. It’s a great exercise but that’s about it for me.
If you are worried about rod bolt failure, measure then when they are new and measure them every time you do updates and see what you get.
