How to Upgrade a 421 Small Block

Concealed Weapon

Steve Dulcich Oct 28, 2013 0 Comment(s)
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Vital Specs: Dr. J’s 421 Chevy Small-Block
Block: Dart SHP
Bore: 4.155 inches
Stroke: 3.875 inches
CID: 421 cid
Compression Ratio: 11.5:1
Crankshaft: Callies Compstar
Camshaft: Isky Hyd Roller
Timing Chain: Cloyes
Lifters: Isky Hydraulic
Pushrods: Manley
Springs: Manley 22441-16
Installed Ht: 1.900
Spring Load, Closed: 170-pound seat
Spring Load, Open: 500 pounds at 1.100 inches
Retainer: Manley 10-degree Titanium
Valve Locks: Manley 10 degrees
Duration Intake: 258 degrees at 0.050
Intake Lift: 0.640 inch
Duration Exhaust: 262 degrees at 0.050
Exhaust Lift: 0.640 inch
Rockers: COMP Cams
Rocker Ratio: 1.6:1
Lobe Separation: 108 degrees
Installed Centerline: 105 degrees
Ring Pack: CP 1.5/1.5/3 mm
Ring Endgap: 0.020 Top/0.025 Second
Piston: CP bullet Pistons
Piston Clearance: 0.005
Main Fasteners: ARP/Dart
Rods: Callies Compstar 6.00 H-Beam
Main Bearings: Clevite H
Rod Bearings: Clevite HN
Main Journal Diameter: 2.49 inches
Rod Journal Diameter: 2.100 inches
Main Clearance: 0.003 inch
Rod Clearance: 0.003 inch
Cylinder Heads: AirWolf 220
Chamber Volume 67 cc
Head Fasteners: ARP Custom Studs
Intake Manifold: Dr. J’s Performance Hurricane
Intake Port Flow: 325 cfm at 0.700
Exhaust Port Flow: 244 cfm at 0.700
Intake Valve: Manley 2.125
Exhaust Valve: Manley 1.600
Cylinder Head Gaskets: Fel-Pro 1144 (0.041 inch)
Piston/Head Clearance: 0.040 inch
Engine Gaskets: Fel-Pro 1206
Carburetor 950-cfm Holley Street HP
Carb Spacer HVH
Header: Schoenfeld
Coil MSD Ignition
Ignition MSD Ignition
Spark Plug Wires: MSD Ignition
Damper: Professional Products
Water Pump: Meziere Electric
Oil Pan: Moroso Oil Pan
Oil Pump: Melling M55a
Oil: Dello 400 30w

Melling Oil 2/17

Adequate lubrication is ensured by the improved oiling system of the Dart block, while a conventional Melling oil pump pressurizes the system.

Airwolf Cylinder Heads 3/17

Taking 23-degree cylinder head flow to extremes are the AirWolf heads from Dr. J’s. Peak flow measures 333/260 cfm, and at the lift used in this build the engine is still tapping into the 320/240 range. Very impressive for a conventional head that does not require shaft rockers.

Moroso 4/17

The large kick-out–style Moroso pan reduces power-robbing windage losses while substantially increasing the oil capacity.

Valvetrain Isky Manley Comp 5/17

The completed valvetrain with components from Isky, Manley, and COMP Cams deliver the high-rpm stability needed for serious power numbers. The Manley springs are installed to deliver 170/500 pounds of spring load.

Intake 6/17

The wide-open intake ports provide a generous minimum cross-sectional area of 2.65- inches—the kind of size needed to make power upstairs.

Fel Pro Multilayered Steel Head 7/17

Fel-Pro’s multilayered steel head gaskets seal the combustion gases, aided by the clamping of a custom set of ARP studs. With the piston at 0.001-inch positive deck, the quench clearance works out to 0.040 inch.

Intake Manifold 8/17

A Dr. J’s ported "Hurricane" intake manifold helps the engine breathe deep, thanks to its fully ported and flow-balance interior. The intake accepts a 4150 carb configuration.


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