Given the displacement offered by the CHP 408 stroker, we were hoping to exceed 500 hp with the TFS EFI system. The Box R upper intake and 351W lower manifold were installed on the 408 with a set of 36-pound injectors using a Vortech aluminum fuel rail. The FAST engine management system was tuned to provide an air/fuel ratio of 13.0:1 (12.6:1 at the torque peak) and total ignition timing of 32 degrees. After tuning, we were rewarded with peak power numbers of 525 hp (at 6,300 rpm) and 530 lb-ft of torque at 4,500 rpm. While the peak power occurred at 6,300 rpm, note that the torque peak occurred at just 4,500 rpm. Having nearly 2,000 rpm between the peak torque and horsepower numbers meant the injected 408 provided a broad powerband. Torque production from the 408 exceeded 500 lb-ft from 3,600 rpm to 5,400 rpm. Torque production exceeded 450 lb-ft all the way to 6,100 rpm. With 525 hp on tap, there is one injected 408 that can provide a knock-out punch. Now throw in the impressive torque curve and extra efficiency of the EFI system and you have the makings of a serious and reliable street stroker.
An MSD billet distributor, plug wires, and Digital 7 ignition amplifier were on hand to ensure adequate spark to the stroker. | 
Here is a shot of the Box R intake system installed on the 408 stroker. Note the bolt securing the two portions of the upper intake. The Box R intake easily cleared the aluminum fuel rails and distributor. | 
Equipped with the Box R intake, the peak power numbers checked in at 525 hp and 530 lb-ft of torque. Torque production from the Box R eclipsed the 500 lb-ft mark from 3,600 rpm to 5,400 rpm. |
The original goal for the 408 was 500 hp. By combining the power production inherent in the added displacement with the airflow offered by the TFS Box R intake assembly, we were able to not only reach our goal, but also surpass it. Equipped with the 351W lower intake and Box R upper intake from TFS, the 408 stroker (supplied by CHP) produced 525 hp and 530 lb-ft. of torque. The big-cube street motor thumped out over 500 lb-ft of torque from 3,600 rpm to 5,400 rpm, making for one impressive powerband. | | |