Considering Ed Lesley’s Grenade Engine Development is a one-man show, we’re always amazed at the many different projects he’s able to complete. Besides the black humor in the name, Grenade Engine Development builds the engines powering a Corvette sports car team that races at places like Sebring, Fords and Chevys in ARCA races, and several other racing series. But Lesley also builds custom engines for hot rods, and that’s what he was working on when we stopped by his shops in Concord, NC.

This is a 427-based big block Chevrolet engine that a customer wanted done to upgrade the horsepower and reliability in his 1968 Chevelle. The customer already had the Weiand blower and Holley carburetor, so Lesely simply moved it over from the old engine to the new, more powerful setup. The final result is an engine that displaces a whopping 540 cubic inches thanks to a Dart Big M Sportsman block and makes 750 horsepower and 625 lb/ft of torque on a laser-flat power curve. Lesley says the blower isn’t pushed very hard and the boost pressure is kept relatively low. That may not sound very sexy, but it means this engine can run all day long without heat problems but still blow the tires off in practically any gear.

The foundation of this build is a new Big M Sportsman block from Dart. The Dart design makes it easy to build big inches and withstand even bigger horsepower numbers with improved oiling, stronger cylidner bores, a beefy bottom end with four-bolt mains and improved coolant flow patterns compared to original Chevy blocks.

Lesley sourced the rotating assembly from Liberty Engine Parts. The forged flat top pistons are pleanty strong but also keep compression down to manageable levels so that detonation won’t be an issue with the blower. Multi Layer Steel head gaskets from Fel-Pro help ensure optimum sealing between the head and the block even with the increased combustion pressure created by the forced induction.

The race-style tie bar lifters are 0.300 long to eliminate clearance issues with the Dart block’s beefy lifter bores. Notice that the tie bars alway face away from the valley walls.

Lesley chose a Cloyes True Roller timing chain set to keep the forged crank and camshaft in proper sequence. We didn’t manage to get a shot of the cam, but Lesley tells us it is a Comp Cams hydraulic roller with approximately 220 degrees of duration for both the intake and exhaust at 0.050 inch lift. Total valve lift is in the 0.600 inch range.

Here’s a look at the forged bottom end supplied by Liberty Engine Parts.

The cylinder heads are new Pro 1 aluminum pieces that bolt right up and keep the original mounting holes for the intake and exhaust but feature improved ports and combustion chambers.

Lesley checks for correct pushrod length.

The Weiand blower and Holley 850 four-barrel carb were pulled off the old motor, cleaned up and checked out, and reused here.

Lesley went with and MSD distributor and ignition to provide the spark.

One of the great advantages of the Chevrolet big block design is the canted valves in the cylinder heads move the head of the valve away from the cylinder wall to reduce shrouding and help air and fuel flow into the combustion chambers more efficiently.

Lesley says he tried to stay mindful that this engine isn’t for a trailer queen show car and would be driven regularly. The fun factor had to stay high, so he concentrated on building a rock solid engine that would be easy to keep tuned (a single carb instead of duals) and run all day long without overheating problems. Still, the finished product can easily boil the rear tires in any gear, so we’d consider that a success.