I know this is a general question, and I know some of the major causes, but I want some other input from other builders.... What causes a motor to throw a rod and put a hole in the block...?

Louie

 

Stress exerted on the rod is greater than the rods tension strength. Most times its not the rod that causes the break, though, Its the rod bolt. If RPM climb too high, the rod bolt can stretch and once that happens...boom. Other causes are too much load put on the rod from more than one culprit (I.E. High RPM and lots of boost).

Most of the time, its the rod bolts that gave way first, though. ARP rod bolts will help with the stretching issue, but not the high boost issue.

 

In my mind, I'd say that it's a bearing failure at the crank or piston. It would be possible to say that a stretched rod bolt would allow for too much clearance and the oil surface would be lost at the bearing, leading to bearing seisure.

If not a bearing failure, then the rod only sees axial loading and although it would be possible to over stress it, other problems would come to bear first.

Of course, that's just my 2 cents.

Wes Vann