SKU: NPR20-GNHM4075K8
MPN: 20-GNHM4075K8
This piston ring set covers a 4.075-inch bore with a metric ring profile measuring 1.2mm at the top, 1.5mm at the second, and 3.0mm for the oil control package. It's a set built for V8 engine builders who need consistent compression sealing and predictable oil control across a full eight-cylinder rotating assembly. The 4.075 bore size lands in the common overbore range for many small-block and big-block builds, making this a working part for both naturally aspirated and boosted combinations. Builders running custom pistons in this bore range will recognize the thin-ring layout as the current standard for reduced friction and better seal at the cylinder wall.
The three-ring stack handles distinct jobs. The 1.2mm top compression ring carries combustion pressure and forms the primary seal against the cylinder wall, while the 1.5mm second ring backs it up and scrapes excess oil down the bore. The 3.0mm oil control package meters the film left on the wall, keeping oil consumption and crankcase blow-by in check. Thinner ring widths like these reduce reciprocating mass and ring-to-wall friction compared to older 5/64 and 3/16 stacks, which matters in higher-rpm builds. This set is sold under part number 20-GNHM4075K8 and covers all eight cylinders of a V8. Pair it with matching rod bearings and main bearings when freshening or assembling a short block.
Reach for this set when assembling or rebuilding a V8 short block honed to a 4.075 bore, or when matching new pistons that call for the 1.2x1.5x3.0mm ring widths. Proper end-gap filing for the intended application — street, sustained boost, or nitrous — is part of fitting any ring set, so check gap specs against your build before final assembly. We stock a broad range of internal engine parts alongside this set, from other piston ring sets to complete engine and component hardware, so you can source the rest of the rotating assembly in one place.
This set is sized for a 4.075-inch bore. That measurement is the finished honed cylinder diameter, so confirm your block has been bored and honed to 4.075 before ordering. Rings must match the bore closely for correct end-gap and seal.
Those are the ring widths in millimeters. The 1.2mm top compression ring seals combustion pressure, the 1.5mm second ring backs it up and controls oil, and the 3.0mm oil ring package meters the oil film on the cylinder wall. It's a thin-ring layout that lowers friction and reciprocating mass.
Yes. The set is packaged for all eight cylinders of a V8 engine under part number 20-GNHM4075K8, so one set completes a single short-block assembly.
Most performance ring sets ship slightly tight so you can file the end gap to suit your application. Street, boosted, and nitrous builds call for different gaps. Set the gap to match your intended use before final assembly for proper sealing and clearance.
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