Jon Kaase Boss Nine Crate Engine

The Jon Kaase Racing Engines Boss Nine is a custom-built replica engine, bringing the iconic Boss 429 back to life for modern applications. At its core, the Boss Nine utilizes a high-nodular cast iron cylinder block, capable of housing displacements from 429 up to 600 cubic inches. This robust block features a 10.30-inch deck height and can be optioned with a race-oriented cylinder block with 4-bolt main bearing caps for displacements exceeding 521 cubic inches. The engine package includes new aluminum cylinder heads equipped with large stainless steel swirl-polish intake valves (2.30-inch) and exhaust valves (1.90-inch), activated by WW Engineering 1.75:1 aluminum roller rocker arms. For 460ci versions, a cast crankshaft is used, while engines 521ci and larger feature a 4340 steel crankshaft, matched with 4340 forged connecting rods and Diamond forged pistons. While the original Boss 429's intake and exhaust ports could affect low-speed response, Kaase's modern Boss Nine incorporates multiple cam phasing strategies to eliminate this issue. Customers can choose between a hydraulic or solid roller camshaft. For compatibility with pump gas, the compression ratio is typically kept at 11.0:1 or less. The engine is configured with a single-plane intake manifold designed for a 4150 or 4500 style carburetor. Options are available for stack injection, blown configurations, or EFI conversions.