The EngineLabs Homegrown Horsepower series focuses on engines that are self-built by the EngineLabs faithful readers, and encompass many different styles and types from mild to wild. 

This particular 421 cubic inch small-block Chevrolet engine build was started as a father/son project while Army veteran Mike Sargunas was stationed abroad in Afghanistan, and was designed to replace a 383 SBC that blew up just prior to Sargunas’ deployment to Iraq in 2009. 

He explains, “I ordered all the parts to build the engine and had my eight-year old son Mikey receiving them and keeping track until I had gotten home. I had every intention to get it back on the road upon returning but took another assignment in Afghanistan from 2011 through 2012. This project has been on the back burner for many years now and feels great to hear that 421 cubic inch monster fire up and drive the neighbors nuts. All while my son has a grin from ear to ear!”

The engine is centered around a Dart SHP four-bolt splayed main engine block with bores finished at 4.155-inch, a SCAT forged crankshaft with a 3.75-inch stroke, a set of Howards Racing Components 6-inch forged steel, bronze-bushed connecting rods, and a set of Probe Industries forged pistons netting 10.75:1 compression. The file-fit moly rings are from Hastings, while King main and rod bearings are installed along with the Dart coated camshaft bearings. 

Sargunas selected a set of Brodix Track 1 CNC-ported cylinder heads with 221cc intake ports and 2.080-inch intake and 1.600-inch exhaust ports. An Edelbrock Victor Jr. CNC port-matched intake manifold was ordered, along with a 950 CFM carburetor from Quick Fuel Technology to complete the induction system. 

The entire valvetrain was picked out of the COMP Cams catalog; an Xtreme Energy solid roller with .576-inch intake and .582-inch exhaust lift, valve springs, COMP’s Endure-X solid roller lifters, Hi-Tech pushrods and roller race timing set, and even their Ultra-Gold aluminum 1.5:1 ratio, 7/16-inch stud mount roller rocker arms get the air popping in and out of the cylinders. 

A fully baffled Moroso oil pan and Melling M55-HV oil pump were chosen to complete the oiling system, and MSD‘s Pro Billet distributor, 6-AL ignition box, and Remote Ignition Timing Control keep the fire lit in the cylinders. Hooker Super Comp 1 3/4-inch long tube headers gets the exhaust out of the engine – right now, the engine is breathing through open headers, but Sargunas has a complete exhaust system on his list of items to complete the car.

The Z28 also has a TH700R4 transmission compete with B&M Megashifter, full manual valvebody and a custom 3800-stall torque converter to go with the Auburn Posi and 3.73:1 gears in the rearend. It’s been beefed up with a set of weld-in subframe connectors, and the power is put to the ground through Edelbrock control arms and Panhard bar in the rear of the car. And last on the list is covering the car in paint – Sargunas is tossing around the idea of a stealth flat black scheme at this point but hasn’t made any decisions one way or the other.

“I taught Mikey how to check the end gaps on the rings as well as the bearing clearances in the bottom end. He did far more than I could have ever expected and even took the finished product to his second grade class for Show and Tell before we dropped it into the car. Although I blew the budget and didn’t have enough to have it dyno tuned and have a cool video we estimate that it’s good for somewhere around 600 horsepower at the crank. ” says Sargunas.

This is a project that little Mikey will remember for the rest of his life. Kudos to you, Mr. Sargunas, for training the next generation of hot-rodders!