The Big M is based on our proven big-block cylinder heads design. We retained the standard intake port locations and rocker stud bosses. This means that Big M heads use the same readily available valvetrain components as our other Race Series big-block heads. (Some of our competitors make you buy expensive pedestal rocker arms if you want a bigger heads for your big-block). You can step up to the Big M without buying a whole new engine combination.

Our airflow experts enlarged and reshaped the Big M's intake runners to increase port volume without sacrificing velocity. Then they developed a high–flow exhaust port that complements the increased intake airflow. The Big M's monster 2.350" intake valves and 1.880" exhaust valves are the perfect match for any large displacement big–block.

Big M heads have all of the features that have made Dart big–block heads the choice of professional racers and engine builders. We use high–density 355–T6 aluminum that is easier to modify and repair than common 356 alloy—and strong enough that is doesn't require thread inserts. The Big M's heart–shaped combustion chambers enhance combustion efficiency, and its standard ductile iron valve seats are compatible with both stainless steel and titanium valves. The raised exhaust ports improve airflow over the short–side radius, yet still fit most headers.

Material: High–density 355–T6 aluminum
Valve Angle: Intake—24° (rolled two degrees)
Exhaust—15° (rolled two degrees)
Intake Ports: 410cc
Combustion Chambers: 119cc as cast; can be milled to 105cc minimum
Intake Valves: 2.350", +.350" long
Exhaust Valves: 1.925", +.100" long
Guide Spacing: Exhaust moved .045" from bore centerline to accommodate larger valves
Rocker Stud Location: Relocated for revised valve angles; longer exhaust stud required (must use stud girdle designed for Dart heads)
Spark Plugs: Gasketed 3/4" reach plugs
Valve Springs: 1.625"