6020-4155 400 Small Block Oldsmobile FX Series -12cc Flat Top Oldsmobile Forged Piston Set 4.155 inch bore Pin Dia.: 0.98" Comp Height: 1.625" Piston Series Option:FX-1 4032 Alloy 390 Small Block Chevy

390 Small Block Chevy

490 Big Block Oldsmobile

428 Gen 5 LT Direct Injection

473 Pontiac Late

41 Effective June 15th 2026

6020-4155 400 Small Block Oldsmobile FX Series -12cc Flat Top Oldsmobile Forged Piston Set 4.155 inch bore Pin Dia.: 0.98" Comp Height: 1.625" Piston Series Option:FX-1 4032 Alloy 390 Small Block Chevy431 Small Block Oldsmobile, FX, Comp Height: 1. 625, 12cc Flat Top , PIN: . 98", Full Floating or Press Fit, Ring Groove: 1. 2 1. 2 3MM, Stroke: 3. 975", ROD: 7, Approx Comp Ratio: 64cc 11. 4, 68cc 10. 94, 70cc 10. 71 Effective June 15th 2026, These Oldsmobile ring grooves have been updated to the new specifications of 1. 2 1. 2 3mm. Parts manufactured prior to this date feature ring grooves with dimensions of 1 16 1 16 3 16.