Engines and Components› Pistons and Piston Rings

United Engine & Machine Co

1 SET KB139.STD/1 SET 4125BM8.STD

$653.84

SKU: U00B KB139KTM.STD

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Special Order
Ships in 4–6 weeks
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Non-Returnable Item
INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Description

This hypereutectic piston kit (UEM-KB139-STD, KB139-STD) is designed for the Small Block Chevrolet (SBC) 400 CID engine (1970-1980). It features a flat top with 7cc valve relief, 4.125" bore, 3.750" stroke, and 5.700" rod length. Made from low expansion 390 alloy with 16% silicon, it includes wrist pins and spiral locks. Intended for high performance applications like marine, drag race, circle track, street, or towing.

Fitment

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Specifications

BrandUnited Engine & Machine Co
Part NumberU00B KB139KTM.STD

Buy with Confidence

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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