Pontiac 350/421 Heads 1-3/4" Hedman Headers Flowmaster 2.50" Crossflow:

Description

First fire-up video of my 1975 Firebird Formula with Pontiac 350 using '092' 421, small chamber/small valve heads. Camshaft is a custom ground UD with .466"/.467" lift - 220°/226° @ .050" on a 111.5° LSA. Cranking compression is 185-190 psi. Headers are 1-3/4" primary, 4-tube Heddmans #28150 with mandrel-bent, full-length 2.50" exhaust system. Muffler is a Flowmaster #42585 Transverse-mounted crossflow with mandrel-bent 2.50" tailpipes and factory-style, 2.50" stainless steel hockey-stick tips. Carb is n 800cfm Q-Jet with .070" main/idle air bleeds, .074" main jets, .045" primary metering rods, 8 in/Hg power piston spring, .037" idle tube restrictions, .046" idle channel restrictions, 'G' secondary metering rod hanger with .029" (CC) metering rods. Transmission is a M-20 Muncie with a 8.5" disc brake 10-bolt with 3.23:1 gears. Car went on to produce 311 RWHP and 325 lbs/ft RWTQ on pump gas through the mufflers. Ignition is HEI with zero ohm carbon button, .080" AC R46SZ plugs .080" gap and 20° BTDC at idle, 8° of manifold vacuum advance (28° total @ idle) 16° centrifigal, 44° total timing.

Keywords

Pontiac, 350, with, 421, Heads

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