When Joe and Mary Todaro decided to purchase an engine from an unnamed online marketplace, they never expected to have to rebuild it virtually immediately. The engine, a 383-cubic-inch small-block Chevy, failed 25 passes after installation — thanks to a failure in the valvetrain that was attributed to improper valvetrain geometry.

The engine did muster a best pass of 11.0 at 125 MPH before the spectacular failure where a rocker arm tip broke, sending a pushrod through the oilpan and ending the engine’s short life.

Enter New Jersey’s Fonse Performance, enlisted to help resurrect the family’s racing aspirations with a number of new components designed for longevity and bracket-racing consistency. After discovering that the main caps on the original engine were moving around, the decision was made to secure a new Dart Little M engine block to save any potential headaches in the future. 

Using a 4.165 bore and forged-steel 3.875 stroke crankshaft, the new engine displaces 422 cubic inches. Eagle 6-inch forged H-beam connecting rods combine with fly-cut JE pistons to achieve a 13.2:1 compression ratio.

“Airflow Research cylinder heads with 2.080-inch intake and 1.600-inch exhaust valves were utilized in the new build. The heads came CNC ported but they had two nasty lips from the cutter on the short side radius. I removed these two bumps to stabilize the airflow. That was the only work performed on the heads, besides a valve job,” Fonse Performance’s induction specialist Dave Godfrey tells EngineLabs. “The intake flows approximately 300 CFM and the exhaust flows 226 CFM. People always want to know the airflow, and it literally drives me crazy. I’m more concerned with the shape of the port, airspeed and cross-sectional area. These heads have good airspeed on the intake side and the exhaust is fantastic,” 

A GM Performance Parts intake manifold received port-matching and a minor cleanup in the plenum area. In the interest of strength, new Jesel shaft rocker arms were used atop the AFR cylinder heads. The camshaft is from Comp Cams and uses undisclosed dimensions. A Pro Systems 4150 carburetor sits on top, and lubrication is controlled by one of Canton Racing‘s oil pans. The engine is now installed in the family’s Monte Carlo for the 2014 race season.

As part of their annual “Dyno Wars” event, the Fonse Performance team had this engine on the dynamometer for a power test. It wasn’t just any power test – the engine was initially run on VP’s C12 fuel, and then switched over to Q16 oxygenated fuel to show off some of the differences in tuning. 

“We do independent testing for VP Race Fuels and we wanted to show with a little tuning the average person can gain a decent amount of horsepower by simply switching fuels,” says Godfrey. “Regardless of the rpm and/or compression ratio, Q16 has made more power across the board. In the heat, an index car may struggle to run the number, so Q16 could make up the performance difference. We do it with our 8.50 Index car.”

As noted in the dyno sheets below, there is a definite performance increase from the Q16 fuel to the tune of 12 horsepower at the peak – but the gains will definitely provide that edge at the track when necessary. Comparing the information, the gains start right at the beginning of the dyno pull and carry all the way through the end of the test results. Although this build certainly wasn’t of the planned variety, in the end the customer is very happy with the results. The Todaro family has an engine they can rely on, that makes power as advertised, with no mechanical issues to boot. A win for everyone!