Product Line: Hydraulic Flat Tappet. heads used on 327/350/383/400 SBC engines without steam holes is Felpro #1003. All Speedmaster 23deg. SBC heads use standard 14mm. x 750" reach, 5/8 hex, gasket seat sparkplugs like NGK R5671A-7, Autolite 3924, Champion RC12YC, etc.
