What is a Napier hook on a piston ring?

A Napier hook is a specific design feature on the second piston ring. It helps to improve oil control by scraping oil off the cylinder wall and also aids in reducing blow-by, which is the leakage of combustion gases past the piston rings.

What does the bore size and ring thickness mean?

The 4.085 inch bore size indicates the diameter of the cylinder this ring set is designed to fit. The ring thickness measurements (0.043 inch for top/second, 0.135 inch for oil) specify the dimensions of the rings themselves, ensuring they fit correctly into the piston ring grooves.

Are these rings suitable for all engine builds?

This set is designated as 'Performance Steel Napier' and is built for demanding applications. While they offer good durability and improved oil control, it's important to ensure they match the specific requirements and intended use of your engine build.

Mahle OE Piston Rings THM-13 4.085 x .043 .135 RW - 3021254

Name: Mahle Rings Performance Steel Napier THM-13 4.085 x .043 .135 RW Plain Ring Set
Brand: Mahle OE
SKU: mahle-oe-mahle-rings-performance-steel-napier-thm-13-4-085-x-043-135-rw-plain-ri-t14-47703
Price: 45.85 USD
Availability: BackOrder

Mahle Rings Performance Steel Napier THM-13 4.085 x .043 .135 RW Plain Ring Set

$45.85

On Backorder

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Mahle OE Piston Rings THM-13 4.085 x .043 .135 RW. This set includes the piston rings needed for one engine.

Key Features

This set includes the piston rings for one engine.
Steel construction for durability.
Napier hook on the second ring aids oil control and blow-by reduction.
Designed for a 4.085 inch bore size.
Top and second rings are 0.043 inches thick.
Oil ring is 0.135 inches thick.

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Product Details

This Mahle OE Piston Ring set, part number 3021254, includes the rings you need to rebuild an engine. The THM-13 designation indicates a specific design for performance applications, featuring Napier hooks on the second ring for improved oil control and blow-by reduction. These rings are made from steel and measure 4.085 inches in bore size, with a 0.043 inch thickness for the top and second rings, and 0.135 inch for the oil ring.

Mahle is a well-known name in engine components, and this set is built to meet the demands of performance builds. The steel construction offers good durability, and the Napier hook design on the second ring is a notable feature that helps maintain a good seal and manage oil effectively, especially under higher cylinder pressures. Proper ring seal is crucial for engine performance and longevity, ensuring efficient combustion and preventing oil from entering the combustion chamber.

When rebuilding an engine, ensuring you have the correct ring set is vital for proper cylinder sealing and oil control. This set is designed for a 4.085 inch bore, so be sure to confirm this matches your engine's specifications before installation. Always refer to your engine's service manual for the correct installation procedures and any specific requirements for ring gapping or seating.