Hey guys I have a 01 5.3 I took apart. i didn't mark the rods and piston to know which cylinder I told it out of. My question is do I have to put the rods and piston back in the same cylinder it came out of.

 

No but the rod caps and rods are married. The correct way would be measure each piston and each bore and put them in the hole that will keep piston to wall clearance in spec. I've used rods and pistons from other motors and never measured and haven't had any problems. May not be correct but worked.

 

piston divet towards the front of the engine as the piston pins are offset to reduce directional noise.
rod bearing tangs will be out towards the pan rails when viewing from the underside

 

Yes they should go back in where they came out of. It could work, but more than likely the bearing clearances / ptw etc etc are not going to be right if you mis-match them, especially on a 2001 motor that has some miles.

Best way to "get it right" would be to measure the cyl bores and all of the pistons and match them as best you can to get the correct PTW. If you didn't take the rods out of the pistons AND didn't remove the main / rod bearings your bearings (with a bit of luck) go back to where they were. I'd clean all the bearings and then plasti gauge them to see if those clearances are ok.

If you took out all of the bearings its going to be hard to guess where they came from, unless there's obvious wear, in which case you may as well replace them. 120$ will get you a standard rod / main bearing set that should get you in the ball park, but still may require more bearings after measuring.

If this is a drag car that's getting boosted and you don't care if it blows up you could just toss it back together and cross your fingers. If this is going back into someone's car that depends on it getting them from A to B I'd invest a bit of time / money into putting it back together correct which will save you the hassle of pulling it back out if something was wrong.

Next time get a sharpie and label stuff !