curtis73

Piston pins or wrist pins are the attachment from the rod to the piston. In an engine, the wrist pin bore in the piston is not centered. In the forward rotation, one side of the cylinder gets the most wear since it is the thrust side. The pin is offset to the outside of the piston in an attempt to even out the thrust loads. If you want to reverse the rotation of the engine, you have to put the piston pin offset on the other side, which almost always means new pistons.

Here is a photo that should help describe what wrist pins are. Its that round pin that goes through the piston and the top of the rod

jacobs4x4

That would not cause it to not run would it? that would just cause bad wear right?

Good old Bill

Wrist pins (most commonly called) are actually piston pins. They connect the piston to the connecting rod. How they change the position of them to control timing or what ever that one member said is beyond me. Am waiting for an answer on that. Only hole location change that this boy is aware of was on the old 360/390 engines to convert from 3.5" stroke to a 3.75" stroke. Different pistons and crankshaft with longer stroke were used to gain the extra 30 cu. in.

Good old Bill

I'll be hanged, I did it again. Two times in the same day on the same thread. I understand that the thrust side of a piston takes a hit as to wear, I was not aware of the fact they are trying to compensate for this. Thank you for the info, jury is out as to me believing at this time.

Temptingfate_84

I really hate to beat a dead horse but I am gonna pitch my 2 cents into this well. Good old Bill got it right by saying that you can't crank a Model A backwards and it run. True. Why: It will not get any fuel. Carburetors only work one way. However, I have personally seen with my own two eyes (believe it or not) a 4stroke, gas burning, modern day engine run backwards. An late80's or early 90's Audi 5cyl, not sure of the year, with the mechanical fuel injection. Once again, not real sure what they call it. The one with the plunger in the intake that resembled a toilet bowl float. the farther the plunger went down the more fuel it injected. It didn't run good or long(aprox. 45 seconds) but it did run...backwards. Oh!!! Just a thought. If an engine was running backwards it wouldn't get oil either. Oil pumps...another one of those one way things. While I am here I am gonna throw Curtis73 off just a little too. Most diesel engines...The wrist pin is centered... I leave you with that....(sorry for the long post) Oh. one more thing, more of just a pet peeve of mine. A motor creates energy using electricity. An engine creates energy using some sort of fuel. We all have engines in our trucks...Not motors... Sorry, that really drives me up a wall...