Dart Marine Cast Iron 496, 8.1L Big Block Chevy Cylinder Heads 

Dart Marine Cast Iron 496, 8.1L Big Block Chevy Cylinder Heads, 320cc, 2.190" x 1.800" w/Valves

Bare Heads only with Valves, sold in pairs.

Material: Superior cast iron alloy
Comb Chambers: 107cc
Intake Valve Dia: 2.190” or 2.250” option
Intake Port volume: 320cc
Intake Port Dim: Factory 8.1L GM
Int Port Location: Factory 8.1L GM Location
Intake Gasket: Factory GM 8.1L Gasket or Felpro # QMS96057
Exh Valve Dia.: 1.880”
Exh Port volume: 128cc
Exhaust Port Dim: 1.530”T x 1.800”W
Exh Port Location: Raised .050” from factory location
Exhaust Gasket: Factory GM 8.1L Gasket or Felpro # QMS95840
Flow, Intake: 341cfm @ .600” lift
Flow, Exhaust: 252cfm @ .600” lift
Flow Wet: N/A
Freeze Plugs: Dart PN# 32860000B 1 3/8 dia. Brass
Head Bolts: Factory GM head bolts + .270 Dowel Holes
Head Studs: N/A
Manifold: Factory GM or Dart
Milling: Min. 100cc .005” = 1cc flat mill only
Push Rod length: Must be measured / Factory GM 8.1L
Push rod Guide Plate: Dart Adjustable PN# 27001230-4
Retainers: 1.250” or 1.550”
Spark Plug: .750” Reach tapered seat
Spring Pockets: Inner step 1.265” outer step1.550”
Springs: 1.250” Dia. w/ Rotator & 1.550
Valve Length: Intake: 5.235” OAL Exh: 5.425” OAL
Valve Stem Dia: 11/32”
Valve Train: Factory GM valve train
Valve Guides: Integral guides
Valve Guide length: N/A
Valve Guide clearance: .3435” I.D (.002” w/ .3415 dia valve stem)
Valve Guide Spacing: Factory GM 8.1L
Valve Seats: Integral intake seat & Hardened ex. seat.
Valve Seat dia. 2.450” Int. & 2.000” Exh.
Valve Seat angles: 45°
Torque: Use factory GM torque procedures, Intake Manifold (M6 x 1) = 106 in lbs Rocker studs (M10 x 1.5) = 37 ft lbs, Valve Cover (M6 x 1) = 106 in lbs
Weight: 150 lbs pr.