Case Studies – Outside John’s comfort range


It isn’t everyday that I pause when someone asks me to tune their vehicle, but this particular Chevelle had me reconsidering.

Gary Avant’s Chevelle is a 383 powered, supercharged Chevelle using Edelbrock’s EFI Pro Flo XT Engine management unit.

Needless to say, a little bit out of my comfort range…..

Big, Bright and Shiny but not enough

Gary has had some problems with tuners in the Bay Area not being able to figure out the Edelbrock Pro Flo XT unit. The absolute best his motor had hit was 333, and with less than stellar torque numbers. Understandably, Gary was upset as his motor build cost him reportedly over $22,000 and 300hp wasn’t going to cut it.

After an hour or two messing around with the rather cludgy controller, I had the 383 humming at 422 hp / 441 ft lbs.

Sadly because of the Procharger’s linear power delivery, peak power could not be realized due to the limitations of the Pro Flo XT unit.

Gary’s unit had tuning increments from 1000, 1500, 2000, 2200 but after the 2200 rpm point, the Pro Flo XT inexplicably jumped to 5000 rpm.

In a rpm range as limited as this 383 provided, the tuning points lacked the proper resolution and from 3000 rpm until 5000, Gary’s A/F ratio plummeted to 10:1. Due to the rigid rpm tables in the Pro Flo XT, I had to send Gary on his way at just 422 rwhp.

He’s more than happy and has since sent the unit in for some customization, he’s very happy with the peak numbers and plans on having me retune while aiming for 500s.

Next up for Gary’s Chevelle, a bigger pulley, a better rpm table and 500 wheel horsepower or bust!

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