When removing material from...
When removing material from the crown of the piston, take care not to hit the skirt or the pin journal. Make sure to deburr and clean before you take your next measurement.
We first start by measuring the base weight of each component and logging them down. Our goal is to get our mean weight within 0.5 grams. Remember, these are precision parts, use precision tools to do your measuring. We don't recommend a mail scale. Try to find a digital scale that will measure to, at the least, 1/10th of a gram. Starting with the pistons, we determined the lightest piston of our group and used that as the target. To take weight off, we choose the thickest areas that would least affect structural integrity. This is usually in the crown on the bottom side of the piston. NPD's box piston design limits how much can be taken out directly from the bottom of the piston, so care is taken when cutting away material.
The big and small end of the...
The big and small end of the rod is measured separately on the fixture. Each side is balanced independently but the overall weight of the rod is kept in mind.
When balancing the rods, we use a balancing fixture to measure both the big and small end. Each side is measured and a base weight is determined much like the pistons; except that both sides have to be balanced. When removing weight from the rod, we cut away at the metal around the big and small ends of the rod. Weight can also be shaved off at the beam itself but be careful not to grind too close to the oil feed holes. Be sure to clean them before every measurement to get an accurate figure.
NPD suggests measuring the...
NPD suggests measuring the ring at the position it sits at TDC. Ring fitment is done with the torque plate installed as well.
Once everything is balanced, we also measured out the rings for the proper end gap. This is also done with the torque plate installed on the block. The generally accepted way to do this is by pushing the rings halfway down to ensure that they're as straight as possible, but NPD suggests measuring the rings at where they'll sit at TDC. This is where the most pressure is forced against the rings and where ring seal is the most critical. The ring end gap is opened up to the manufacturer's specifications. NPD pistons are made of 4032 aluminum instead of 2618, consisting of higher silicon content. Since the expansion rate is lower on a 4032 piston, we can close up the ring gap. This will decrease the overall amount of blow by we get and burn much less oil; commonly experienced with forged pistons.
We use a ring filer to get...
We use a ring filer to get a better finish on the edge of the ring. Our ring filer also features a dial gauge, which gives us a better idea of how much material to take out.