We are building a high compression, normally aspirated 2.4 motor for a friend of ours to go into a 1998 Neon.
If you didn’t have the machine shop balance your components, then before installing the piston and rod assemblies in the block, you might want to check to make sure the balance of the rods/pistons are as close as possible.
For example, the OEM factory balance allowance should not differ more than 5 grams from the heaviest to lightest rod/piston assembly. This motor we are building with stock 2.4 SRT-4 rods and JE pistons had a difference of 9 grams between the lightest to heaviest rod/piston assembly. Looking further at the rods, three of the rods had extra casting bosses on the small end of the rod and one did not. So, using the proper equipment and balancing techniques, we were able to balance the 4 rod/piston assemblies within .25g of each other.
This may sound trivial, but with this motor is spinning close to 8000 rpms, you want the balance of the motor to be as good as possible or it may not live as long as a balanced motor would and could run very rough.
So, next time you are assembling a bottom end and didn’t pay for the machine shop to do any balancing, you can go down to your local office supply and pick up a scale that measures in grams to double check your components before you assemble your motor.