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SPEED PRO · FED-R921035 Speed Pro · FED-R921035 Speed Pro Piston Rings, Plasma-Moly, File-Fit, 4.125 in. Bore, 5/64 in, 5/64 in, 3/16 in. Thickness, V8, Set Plasma-moly rings built for the heat and load of serious V8 work.
▸ Plasma-moly top ring runs cooler with less friction under load▸ File-fit design lets you dial in end gap precisely for your bore▸ Correct gap means ring lands survive extended WOT and repeat runs▸ 5/64 top, 5/64 second, 3/16 oil — proven street/strip dimensions▸ Supplied oversized so nothing is left to chance at the ring filer
Australian-owned. Stocking circuit racing parts, track-day essentials, and performance upgrades.
Speed Pro Piston Rings, Plasma-Moly, F… $325.67
Add to cart Made to order · availability confirmed when you order
Home Shop Garage Account incl. GST · ships AU-wide
● Made to order We confirm availability with our supplier when you order. Confirm availability with us — quick reply, usually same day
Specifications
On the spec sheet. Spec sheet coming — contact support for full spec details. Fitment
Will this fit? Fitment data still being indexed for this product. Ask BuildBot for a fit-check against your vehicle.
Why this part
Cast iron rings compromise under sustained heat. The plasma-moly face coating on the top ring resists wear and transfers heat away faster, which matters when the motor is loaded hard run after run. File-fit construction means the end gap is set for your specific bore and application, not averaged across a production run — that precision is what keeps ring lands intact.
Pairs well with
Other parts in this build. © 2026 TrackTheory · ABN 33 689 482 504 Built in Adelaide · Shipping AU-wide
