Beat Power-Robbing Friction with Hastings Steel and Stainless Steel Series Piston Rings

Friction is the enemy of engine efficiency, robbing an engine of horsepower and fuel economy. The biggest offenders are piston rings—up to 60% of an engine’s internal friction is caused by ring movement in the cylinders.

For the OEMs, the answer was to use thinner piston rings. Modern ring technology allowed GM to go from the traditional 5/64-5/64-3/16-inch ring pack used for Gen I small block V8s to a 1.5mm/1.5mm/3.0mm ring pack for the LS engine series. That’s a serious reduction in ring thickness, with a corresponding reduction in friction.

Top Rings
The Stainless Steel Series Ring Sets have a 1.2mm stainless steel top ring that is gas-nitrided to increase the hardness of the outside diameter and sides of the ring. This hardened layer provides excellent wear and scuff resistance. It also makes the ring more resistant to micro-welding, a condition where material from the piston groove is transferred and “welded” to the ring material. This prevents the ring from moving freely in the groove or can cause the ring to get stuck in the groove.

The top rings have a .145" radial wall which allows for proper back clearance (the area behind the ring and the bottom of the piston groove) with most performance pistons on the market. The rings also have a convex, or barrel shape that optimizes oil film lubrication and provides better sealing at a specific contact point on the cylinder wall. Hastings laps the rings in a cylinder to obtain this surface shape, eliminating the need to ‘break-in’ the rings after engine assembly.

The Steel Series Ring Sets have a 1.5mm top compression ring made from SAE9254 alloy steel (the same steel used for valve springs) that is stronger than grey or ductile cast iron. The rings have a molybdenum (moly) plasma coating with nickel and chromium. This coating is applied to the rings by filling a channel in the steel wire with moly using a plasma thermal spraying process. Moly is a great surface coating due to its excellent wear and scuff resistance. The coating is also slightly porous, increases its ability to retain oil for better lubrication.

The 1.5mm rings have the same .145" radial wall and barrel face profile as the 1.2mm stainless rings and have the same performance characteristics.

Secondary Rings
The secondary rings are made from spheroidal graphite cast iron. This material has good ductility and strength, which allows the ring to be twisted without the fear of fracturing. The Stainless Steel Series ring sets have 1.2mm rings with a .145" radial wall to work with aftermarket performance pistons. The Steel Series ring sets have 1.5mm rings with a larger .163" radial wall to match the deeper grooves of the pistons they were designed for.

The ring profile has a hook groove, or step so the bottom of the ring fits tightly to the cylinder wall. That improves oil scraping and acts as a reservoir for stored oil to drain back to minimize any upward oil migration past the ring.

Oil Control Rings
The Stainless Steel and Steel Series ring sets have a 3.0mm Flex Vent Control oil control ring. It uses two chrome-plated carbon steel rails on each side of a stainless steel flex expander ring. The principle function of the Flex Vent assembly is to meter the oil film on the cylinder wall for proper piston lubrication. The expander supports the rails in the piston groove and applies force on the back of the rails so they scrape oil from the cylinder bore.

The oil control ring has slighter higher oil tension than other “low tension” oil rings—13 lbs. versus 10 pounds. During engine testing, Hastings found the 13 Ib. oil rings do a better job controlling oil while keeping friction and horsepower losses to a minimum.

Summit Racing carries Hastings Stainless Steel and Steel Series Piston Ring Sets to fit a large selection of bore sizes. Now that you know how good they are, pick up a set for your next engine build.

SEE HASTINGS STAINLESS STEEL AND STEEL SERIES PISTON RING SETS AT SUMMIT RACING