PowerNation TV’s Engine Power Shows You How to Build a 427 CID Small Block Chevy

Put in the correct order, the numbers four, two, and seven have an almost mythical aura to the Bowtie faithful (and technically, Ford enthusiasts too). Traditionally, 427 denoted Chevy’s top-dog big block V8 as installed in 1960s supercars like the L88 Corvette and ZL-1 Camaro.

But nowadays, you can build a 427 cubic inch small block Chevy that delivers big power in a smaller, lighter package. The formula is simple—a block with 4.125-inch bores and a 4.000-inch stroke crankshaft.

In the olden days that meant finding a block for a 400 cubic inch Chevy, which came from the factory with 4.125-inch bores. And if you managed to find one, you prayed that a sonic check would reveal little to no core shift, meaning the bores were nice and straight.

That is no longer an issue thanks to aftermarket blocks like the Summit Racing SPC Engine Block. Engine Power's Pat Topolinski and Frankie Forman used to build their version of a small block 427. The block is a brand new, heavy-duty casting that can handle up to 700 horsepower. They are cast in a state-of-the-art German foundry and precision-finished in the USA on high-speed machining centers.

Pat and Frankie will show you all that plus the rest of the 427 assembly process in the “Building a 427ci Pump Gas Small Block for Ultimate Street Domination” video on the PowerNation YouTube channel. We think you’ll be pleasantly surprised at how much power this engine makes on pump gas.

If watching that video gets you all fired up to build your own small block 427, you’ll find all of the stuff Engine Power used to build theirs in our parts list.

Here’s a quick overview of the major components.

Reciprocating Assembly
The 427’s reciprocating assembly is based around a Summit Racing Forged Crankshaft (SUM-SBC35040002P). The 4340 forged steel crank has .125-inch journal radii for additional strength.

The Summit Racing™ Performance SBC Connecting Rods (SUM-SBC4274125) are also made from 4340 forged steel. They have an H-beam design and ARP2000 bolts rated to 220,000 PSI.

The Summit Racing™ Forged Pro Pistons are made from 2618 aluminum for strength and weight savings. The pistons have a pump gas- and boost-friendly 18c effective dish and skirt profiles designed to run at tighter clearances for less piston rock.

The pistons are fitted with 1.2/1.2/3mm Summit Racing™ Pro GPX Gas Ported Piston Rings. They have a slotted top ring that allows gas pressure into the ring groove and exert outward and downward force on the ring itself. That extra force stabilizes the ring, increasing ring seal to reduce blowby and improve horsepower production.

Oil System
The 427’s oiling system is based around a seven quart Moroso Street/Strip Oil Pan and a Melling Shark Tooth Oil Pump. The Moroso pan is clearanced for crankshafts up to 4.125-inch stroke. The baffled pan has driver and passenger side kickouts for improved ground clearance and comes with a windage tray and crank scraper.

The Melling Shark Tooth oil pumps utilize helical asymmetrical gear technology to provide 10 to 25 percent more oil with smooth operation to reduce distributor gear and intermediate shaft wear. Tighter gear tip-to-housing clearances reduce internal leakage and improve pump efficiency.

Camshaft
Engine Power chose a Summit Racing™ Pro SBC LS Firing Order Hydraulic Roller Camshaft for the 427. Using the GM LS engine firing order for a traditional small block Chevy improves combustion chamber cooling to reduce the chances of detonation. The configuration also improves air/fuel mixture distribution and helps reduce engine vibration and bearing wear.

The cam is a Stage 6 grind designed for 383 CID or larger engines. 3.73 rear axle gears and a 3,500+ RPM stall converter are recommended.

Specifications
• 3,000-7,000 RPM operating range
• .248° intake/.256° exhaust duration at .050-inch valve lift
• 0.550-inch intake and exhaust lift
• 110° lobe separation

Cylinder Heads
The Trick Flow® Super 23® 230 Cylinder Heads are designed to provide the higher RPM performance of 18-degree race heads while using affordable components made for 23-degree heads. The Super 23 230 heads have Trick Flow's advanced CNC Competition Ported runners and combustion chambers. The premium high resolution surface finish allows maximum flow and performance.

Specifications
• 230cc intake and 78cc exhaust runners
• 70cc combustion chambers with 2.080-inch intake/1.600-inch exhaust valves
• 1.550-inch dual valve springs rated to .680-inch valve lift
• Manganese bronze valve guides, ductile iron valve seats, 10-degree valve locks and retainers
• Guideplates and rocker arm studs included

Valvetrain
The Trick Flow Super 23 cylinder heads are fitted with valve springs designed for solid roller camshafts. These springs are too stiff for use with the Summit Racing Pro SBC cam Engine Power chose, so they were replaced with Trick Flow by PAC Racing Valve Springs designed for hydraulic roller cams. The 1.550-inch dual springs are rated at .625-inch of valve lift.

The Jesel Sportsman Roller Rocker Arms are designed for high-flow cylinder heads like the Trick Flow Super 23 230s. The shaft-mount rockers have a 1.7 ratio, are more stable than stud-mount rockers, and reduce friction to help unleash more power.

Summit Racing™ Chromoly Pushrods are made from cold-forged 4130 chromoly steel. The one-piece pushrods are 5/16-inch in diameter and have .080-inch thick walls to reduce flex at high RPM.

Intake Manifold and Carburetor
The Edelbrock Super Victor II intake manifold is designed for large cubic inch small block Chevys with aggressive cams and high-flow cylinder heads. The single-plane intake has a high-rise profile with extra-long runners that extend into the plenum for increased volume. The intake has a 4,000-8,000 RPM range.

Engine Power used an 850 CFM Edelbrock VRS-4150 Series Carburetor. It has fuel bowls with 20% more capacity plus internal ribs and baffles to reduce fuel slosh and aeration. Jet extenders in the rear keep the jets covered under hard acceleration. The idle circuit uses interchangeable discharge jets at each corner so you can dial in a smooth idle when using big, low-vacuum camshafts.

Distributor
Engine Power fitted the 427 with a FiTech Go-Spark Distributor. It has dual high-output magnetic pickups and paddle wheel reluctor to create a strong, stable timing signal. The pickups are placed 180° apart to provide a redundant ignition system for racing applications. Other features include an adjustable mechanical advance, CNC machined 6061 T-6 aluminum housing, and a compact bowl/cap design to fit in tight spaces. 

Other Parts
Engine Power used these parts to complete the 427 build:
• Clevite and Summit Racing Bearings
• Summit Racing™ Bracket Racer SFI Harmonic Balancer
• Cometic MLS Cylinder Head Gaskets
• Summit Racing™ Billet Electric Water Pump
• Hot Shot’s Secret 10W30 Adrenaline R-Series Racing Oil

CHECK OUT THE ENGINE POWER 427 CID SMALL BLOCK CHEVY PARTS LIST