Most Pontiac blocks can accept a 0.060-inch overbore. This particular 400 had already been bored 0.030-inch, but didn't need to go to 0.060 to restore the cylinder-wall surface. Sealed Power offers a number of high-quality forged-aluminum pistons for various Pontiac V-8 engines. It's one of the few companies producing 400 pistons for a 0.040-inch overbore (PN L2262F040). Based on Pontiac's original design, the high-quality durable units were ideal for our application.