Project Best of Both Worlds 427 Chevy Parts Combos Now Available at Summit Racing

Mike Mavrigian of Birchwood Automotive has built yet another awesome engine. This one is a 427 cubic inch small block Chevy based on World Products’ Motown II LS block, which lets you use free-flowing GM LS cylinder heads on a Gen 1 short block. The combination produced a respectable 641 horsepower at 6,300 RPM, and 555.7 lbs-ft. of torque at 5,200 RPM.

The 427 is an involved build—read the Best of Both Worlds build articles at OnAllCylinders to learn more, then take a look at our Best of Both Worlds 427 Chevy Parts Combos to see the complete list of components.

Short Block Combo
The Motown II LS block accepts small block Chevy or LS motor mounts so you can bolt it into vehicles that came with either engine. The block also accepts Gen 1 Chevy accessories like the transmission, water pump, distributor, oil pan, and bellhousing. World Products also makes a valley plate just for the Motown II block.

The bottom end features a SCAT forged crank and connecting rods, JE forged pistons, and Clevite bearings. The Motown II block requires a dedicated hydraulic roller cam, which is available from COMP Cams by special order.
Cam Specs
• 243° intake/251° exhaust duration @ 0.050”
• 0.624” intake/exhaust valve lift (with 1.72:1 rockers)
• 0.363” intake/exhaust lobe lift
• 114° lobe separation
• 111° intake centerline

Oiling System Combo
The 427’s oiling system is based on a Gen 1 style Moroso Street/Strip oil pan and a Melling standard volume oil pump with a Moroso pickup. The pan seals to the block with Fel-Pro gaskets and ARP pan studs. A Summit Racing oil filter adapter with a built-in oil bypass and a Moroso Twist-Lock dipstick were used as well.

Top End Combo
The top end is based on a pair of Trick Flow GenX® 235 LS cylinder heads fitted with COMP Cams Ultra Gold roller rockers and Trick Flow pushrods. Air and fuel delivery is handled by an 850 cfm Holley Ultra double pumper carburetor on a Holley LS Mid-Rise intake manifold. The ignition system is all MSD—Pro Billet distributor; 6AL Digital box; Super Conductor wires; and a bronze distributor drive gear.

Cooling System Combo
The cooling system for the World Products Motown II LS block routes lines from each side of the block to a Moroso thermostat housing and water neck mounted on one of the cylinder heads. A Meziere electric water pump circulates the coolant through the engine. The system was plumbed with -12 AN fittings and hose from Fragola and Aeroquip.

Steam Line Combo
LS cylinder heads require a steam line system to properly evacuate air and avoid overheating at the rear cylinders. The system for the 427 was plumbed with Trick Flow and Fragola -4 AN fittings and hose.

Completer Combo
This combo includes Summit Racing Gen 1 style valve covers; COMP Cams adapters to fit the valve covers on the Trick Flow GenX LS heads; and a pair of Hooker Super Competition full length headers. It also includes a Fluidampr harmonic damper and other small parts to finish the engine assembly.

SEE THE PROJECT BEST OF BOTH WORLDS 427 CHEVY PARTS COMBOS AT SUMMIT RACING