The Stovebolt Site Forums The Shop Area Engine Shop Throwing a rod.

What exactly happens when an engine throws a rod?

I'm guessing that the connecting rod bearing wears to the point that it becomes loose on the crankshaft, which in turn causes more wallowing out at a faster pace. Finally to the point that the rod is slapping around inside of the engine hitting things it shouldn't, hence the hammering sound. Left unattended to it will eventually come out the side of the block.

Is this anywhere near correct?

If so, can a person simply replace the connecting rods when the initial sound is first detected and continue using the engine?

Yesterday my 216 started making initial sounds of a rod being thrown. Since the block is cracked and semi-repaired with J-B Weld I opted to drive the truck as far back toward home as possible. I drove almost 40 miles before arriving at my farm and the rod never did completely go out. Granted it kind of sounded like a blacksmith at work, but was still running.

Guess I'll go start the process of swapping another engine into the truck. I think I'll install another 216 that I already have for now, then do some work on a 235 I already have and install it later.

Shade tree mechanic? Nope, not even a tree at my farm to work under. After all this is Kansas and we can't all be lucky enough to have trees growing.

generally, a "thrown" rod is one hanging out the side of the block-usually a tough fix. you sound like you have one spun, which in a babbitt engine isn't really "spun" either. A crankshaft & rod(s)is needed to repair-easiest for ther novice to swap engines at this point. 235s can be found dirt cheap as folks toss them for 350/th350 combos. brian

Hey neighbor, you've discovered the real weakness of a babbetted engine that's been over-reved it sounds like. A babbetted engine will last forever IF you keep it at or below 3200RPM. You can get more usable RPM if you put aluminum pistons in the engine. I never get my 38 over 60 MPH (normally cruise at 55) & I have the 3.73 rear end.

Todo? I dont think we are in Kansas anymore. Yep got ya one of those throw rods. Now if you was back in the day you could have stoped the engine knock on the side of the road. You would have pulled the pan, undone the rod cap, cut off a length of your leather belt and wraped it around the crankshaft, assembled it again and you would have been good for a day or so.

I haven't a tach so I don't know what I've been revving it up to.

I've had the truck for 9 years with it being my only vehicle for a majority of that time so I consider it having lasted well for a babbitt bearing engine.

Because of the cracked block I considered the engine expendable so have indeed driven it hard at times.

The truck has different differential gears so moved pretty easily down the highway.

Thanks for the replies. Everyone having a safe Fourth holiday period?

when you throw a rod basicly the rod breaks in two and rattles around while the engine runs

If the motor still runs good you might try reshimming the knocker. Or you could just drive it the way it is you will probly get tired of the knock long before the rod ever gives it up.