The die-hard Ford junkies at Jon Kaase Racing Engines have brought the Boss 429 back to life on its 40th anniversary.
Available as a NASCAR homologation special in ’69-’70 Mustangs (and two special Cougars), the Ford faithful have been lusting for a new Boss 429 engine ever since. Now it’s available again from Kaase as a modern Boss 429 combination is based on a high-nodular cast iron cylinder block that can accommodate 429, 460, 521, or 600 cubic inches, with output extending from 500 to 1,000 streetable horsepower.
Kaase allows that displacement beyond 521 cubic inches include a race-oriented cylinder block equipped with 4-bolt main bearing caps. The 10.30-inch deck height block receives a cast crankshaft in the 460ci version (600hp). Engines with 521ci and beyond are founded on a 4340 steel crankshaft joined with 4340 forged connecting rods and Diamond forged pistons. For use with pump gas, the compression ratio is usually limited to 11.0:1 or less.
Kaase caps the short-block with new aluminum cylinder heads fitted with stainless steel swirl-polish 2.30-inch intake and 1.90-inch exhaust valves activated by WW Engineering 1.75:1 aluminum roller rocker arms. Though the rather large ports and marginal cam specs of the original 429 hampered low-speed response, the multiple cam phasing applied to Kaase’s Boss 429 engines has eliminated this problem. Customers also have the option of a hydraulic or solid roller camshaft.