Building a Dirt Modified Racing Engine

February 27, 2018 / by Matt Panure

Follow along as Baril Engine Rebuilding in Green Bay, Wisconsin assembles a project engine from Circle Track Magazine.

The engine is the heart of any racecar. In the circle track world, that is no different. Follow along as Baril Engine Rebuilding in Green Bay, Wisconsin assembles a project engine from Circle Track Magazine. Based on World Products’ new Pro Light-Weight Small Block Chevy block, the engine will hit the track in Benji LaCrosse’s Modified race car next season.
Baril honed the cylinders to meet the specs of the pistons from JE.
Baril fitted the crankshaft with bob weights on the balancer. The bob weights simulate ring set, piston, wrist pin, spiral locks, rod bearings, and oil-factor weight. It represents the whole rotating mass of the engine.
JE sends a spec sheet with every set of pistons. Here is what went in our engine.
Baril uses a gram scale to ensure accuracy. As you can see, the piston weighed in at 429.6g.
The 6-inch connecting rod attached to the crankshaft for the dry assembly. The whole assembly came together very well, and all the clearances were on par.
One of the most important measurements in the dry assembly (checking) process is deck height. The desired deck height with the JE Pistons was three-thousandths below the deck. Of course, everything ended up right on the money.
The installation of the cam was a very intricate process. While some engine builders will use tools, Baril uses two long bolts to hold the cam and slide it in. It is critical that the cam bearings don't get scratched when installing. We used Erson's very popular E116410-NIT. It is a mechanical flat tappet grind.
Before installing the rods and pistons, Baril did a quick check of the ring gaps.
Here we see one of the rings in the ring filer tool. JE will supply the ring end gap specs by application.
Rings are installed on the JE pistons before installing them into the block.
Baril put a degree wheel and dial indicators on to check that the cam was degreed to Erson's specs. The gauge on the far right checks to make sure the pistons are at TDC. The gauge on the left is checking valve lift.
The front end of our engine with power steering and water pumps. Installation was a breeze, and the pulleys lined up perfectly.
The dyno numbers for Project Dirt Modified Engine with the timing at 38 degrees and the one-inch open spacer attached.
The dotted line signifies our first pull at 34 degrees of timing and no carb spacer.
Project Dirt Modified Engine is back from being displayed at PRI and is ready to run in 2018!

How Powerful is the Engine?

The engine was placed on the dyno at Motor Masters, where George Forge broke it in and tuned it for max power. The first tests used a Holley 750 carburetor, no spacer plate, and 34 degrees of timing. With the baseline set, Forge first experimented by advancing the timing two degrees at a time. Max power and torque were achieved at 38 degrees. Forge then put various spacer plates on the engine to see what gains he could make. An open one-inch spacer made the engine the happiest, where it maxed out at 544.4 HP at 6,600 rpm and hit a max torque of 495.3 at 5,000 rpm.

What's Next for Project Dirt Modified Engine?

We know it runs. We know it makes power. But will it make it into Victory Lane? Unfortunately, the build was finished a little too late in the race season to install and put into action. However, the short track racing season is just around the corner in Wisconsin. While the ground is covered in the cold white stuff, the engine will be installed into Benji LaCrosse's 2018 racing machine. The plan is to follow along as the engine is installed and document what happens when it finally hits the track.

Topics: ENGINE BUILDS, featured, ENGINE TECH, Tech

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Written by Matt Panure

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