The '400 SBC Trick': Larger Bore, Shorter Stroke
At 3:43 in
History of Chevy's NASCAR Engines: Small Block Evolution Details Up Close With a Legend (SB2 & R07)
What happens here
The quest for increased horsepower led to the desire for larger cylinder bores and shorter strokes, as this configuration allowed cylinder heads to 'breathe' better. The Chevrolet 400 SBC engine was identified as a suitable candidate due to its larger factory bore. However, the standard 400 SBC came with two-bolt main caps that were weaker than the four-bolt caps of a 350 SBC. Engine builders modified the 400 block by installing custom billet main caps (sized for the stronger 350 mains) using spacers, and then line-boring the assembly to precisely fit a 350 crankshaft. This ingenious adaptation allowed racers to combine the desired bore size with improved block rigidity, laying the groundwork for future high-performance small blocks.
Goal: Explain the modifications to the 400 SBC engine for enhanced airflow and durability.
Tools and materials
- Billet Main Caps — Providing stronger main bearing support for the 400 SBC block
- Chevrolet 400 SBC Engine Block Chevrolet — The base engine block chosen for its larger bore
- Rottler F69A Machine Rottler — Line-boring the main caps for precise crankshaft fitment (shown in background)
- Spacer Custom-made — Adapting the 350-sized main caps to the 400 block
What they say
(936 characters)Hide
What they say
(936 characters)Auto-generated from the video audio.