piston and rod assembly

[sam24fan]

I spun all rod bearings. I went and got used rod and pistons. Well they didn't number any when they pulled them from another motor. There are no marks on the pistons to let me know which is the front. The books say there is an arrow on top of piston, well there isn't. How do I tell which is the front of these rods and which cylinder to place them in? I can't go buy the old ones because they were put in all kinds of ways when looking at the tang.

Please someone let me know how to resolve this problem!

[GTP Dad]

Are these pistons flat top with valve reliefs in the top. If they have valve reliefs simply place the valve reliefs to the circle is pointing toward the exhaust not the intake. If you don't have valve relief's then you really won't be able to tell which way they go although you may want to insert them into the cylinders to make sure that they fit properly and move freely before connecting the rod.

As for the rod caps you will just have to hit and miss on those since they are usually bored to match each other. There are usually little marks on the caps, they look like lines, one on the cap one on the rod. If you match those up you should at least have them in correctly. Next time make certain they mark them if you purchase used rods so they can go back together properly. Good Luck!

[richtazz]

Take them to a competent machine shop, they will be able to tell you which way they go in the block. Have them recondition the rods to true up the bottom end that way it won't matter where you put them back in.

[maxwedge]

One tip on the con rods is there is a chamfer on either side of the rod and cap at the parting face, the larger chamfer always goes to the outside of the crank journal, so if there are valve reliefs there can only be 4 that would fit the crank properly in that situation, assuming the reliefs are different sizes, some pistons have offset pins that create a one bank only fit.