Hell bent for Leather, why couldn't metal stretch. Now, I should clarify, rod stretch is not always a bad thing, my wife likes it when my rod stretches
Ok, I'm not going to be drawn into another debate but...... I'm pretty sure stretch is possible and can happen to metal literally. Especially at 15,000 RPM I'll confirm the term "stretch" with my dad when I get a chance, he's forgot more about metal than most of us know.
I belive you are correct about stretch.We were just talking about that at the shop.As far as I know it does. As far as the TL, that was not the case.It was like acid eating away at the parts.That's why they tell you to drain and flush da stuff
Funny, but no that's not why they tell you to drain the stuff. But since you brought it up. I was told at the dealer show a couple of weeks back by the Director of Nutec that since the change from Special-4 to Special-5, it is no longer necessary to drain and run some pump gas through. The reason they recommended draining and flushing of Special-4 was because there were chemicals that were corrosive to gaskets and rubber o-rings. Both of which are used in most carburetors. But again, that's from the past. If Nutec could melt or eat metal it would be all over my garage right now. It comes in metal barrels ya know, now come on, enough with the melt down crap
Yes metal can stretch!! But Tracee is right it is due to fatigue. The technical term is Plastic Deformation. This is seen in tensile tests. That test is where a piece of metal is put into a machine and pulled into two pieces. The metal will go through two stages. 1st Elastic deformation, this is where the force is stretching the metal but if the force is released the metal will go back to its orgional shape. 2nd Plactic Deformation, This occurs right after the Elastic stage and also happens right before it fails (breaks). If the force is released before it breaks there will be a change in the shape of the metal. It has began to neck down. It is very neat to see this happen. When it breaks it just pops. This type of thing can easily happen to a con rod, espically one with a heavy piston. That is your strength of materials/destructive testing/physics lesson for the day. Now go home and do your homework and be ready for your quize on Monday. Crispy
Rod stretch is common in high RPM engines. Varies with the material used in the rod, i.e., aluminum rods stretch more than steel. Depending on the application, a few hundreds of an inch is not out of the question. The properties of metal can be fascinating. I'm always amazed about the stories of the SR-71 Blackbird spy plane - it was constructed "loose" because the airframe supposedly stretched in flight - somewhere between 8 inches to over a foot - about 1% of its total length. On the ground it actually leaked fuel all over the place. When it heated up in high speed flight it sealed itself up.
I just wanted to thow something into the "acid " mix. High grade motor oils have additives that break down the acids produced during fuel burn. Don't ever skimp on oil. Use the good stuff.
