Ok, so this is my first time rebuilding an engine. I've done a lot of stuff over the years, engine swaps, Trans swaps, built a rear end, etc, but this is my first time actually rebuilding an engine. I'm installing my pistons the other night and I notice that the 1-2 pistons have about .020 side clearance, then I get to the 3-4 journal and I notice that the rod bearing caps are butted up against each other and I can't even wiggle them. The assembly is an eagle street performance assembly with cast crank. The pistons have a dot on top and two letter F's on one side of the piston pistons, same side as the dot. I assumed that the F's meant front. So that's how I installed them. I only have 6 pistons in right now. After looking online a little bit, I find that most aftermarket rods have a chamfer on one side that goes against the crank and that the bearings have a fillet radius on the same side to match the crank. Does this have any relationship to the dot on top of the piston or the F's on the side? Could I have the pistons in wrong on the 3-4 journal and that's why I have no clearance?

 

Pistons sound like they're in properly with the F towards the front but that doesn't mean the connecting rods are installed properly on the pistons. Unless everything was marked, you probably only need to swap the 3/4 pistons and rods to the opposite side so that the conrods are on the crank properly.

Odd number piston rods will be on the forward side of the journal. Even numbered piston rods will be on the back side of the journal. Since swapping from side to side won't change the position of the piston in the cylinder (The F will still face forward) it will however change the rod location on the journal. If the 2 rods are backwards on a journal, swapping from side to side will fix the issue.

 

Does the F's have to face the front?

 

The dot goes towards the front of the engine (the letter F's don't exist on most pistons but since they are on the same side as the Dot, they clearly indicate 'front' as well in your case).

Rods have an orientation as well, like Alky says. The side with the clearance for the crank radius goes towards the end of the rod journal, obviously, since that's the only side that has a radius to clear. Another way (easier way) of figuring it out is that the locating notches in the rods/rod bearings ALWAYS point outwards towards the oil pan rail for whichever bank they are installed on.

So.... notches out, F's pointing forward in all 8 and you're home. If one of the two is wrong, it's on the wrong bank of cylinders. If both of them are wrong it's on the correct bank but you need to flip it 180*.

Sounds complicated, but once you see it in action once or twice you'll be a pro and ready to help others assemble their engines!

 

And don't forget that moving rods and pistons around, the motor may need rebalanced.

 

Thanks for the help guys. I got it all straightened out. It's really not that to understand, I just didn't know it had to be that way. Now all my side clearances are Ok.