The naturally aspirated C6 Z06 responded well to tuning modifications, but would the C7 Z06’s supercharger make finding additional tire-shredding power from GM’s new supercar a challenge? Fortunately, supercharged engines love to breathe, and the power-hungry folks at Hooker BlackHeart Speed Exhaust found room for improvement in the OEM cast-iron exhaust manifolds.
The engineering team at Hooker developed a tubular shorty header that’s a direct OEM replacement and features 1 7/8-inch primaries and a unique, 4-into-1 inline merge collector. They’re hand-welded from 304 stainless steel and include fully blended welds at the flange and collector for maximum exhaust gas velocity and scavenging. Besides saving 19 pounds over the stock castings, the headers add 11 horsepower and 14 lb-ft of torque in the meat of the power curve. (We’d expect much larger gains with other modifications and a proper PCM tune.) These 304 stainless steel works of art fit 2014-current (C7) Corvettes, including the Z06.
We joined the Hooker BlackHeart Speed Exhaust team at their research, development and manufacturing facility in Bowling Green, Kentucky, to witness installation and testing of their shorty headers on a 2015 Corvette Z06. Follow along for the details.
01. Before putting our test subject under the knife, we strapped it to Hooker’s in-house Dynojet dynamometer for baseline power figures. The rollers measured 568 horsepower and 584 lb-ft at the stock Z06’s Michelins.
02. Hooker’s installation expert Clint Belcher began the process by disconnecting the battery.
03. Next, Belcher removed the skidplate and chassis braces between the front crossmember and the frame.
04. After loosening the rear clamps and disconnecting the front flanges, Belcher removed the factory mid-pipe.
05. To give us a bit more working room, Belcher drained the engine oil and disconnected the dry-sump hoses. Plugging the hoses and lines kept the mess to a minimum.
06. Next, Belcher removed the nuts securing the catalytic converter downpipes from the manifolds.
07. Hooker Development Engineer Doug Marino started work on the topside of the engine by disconnecting the PCV and vacuum lines from the rocker covers, dry-sump system and brake booster.
08. The power distribution box needed to be removed to allow access to the right side manifold. Marino started the procedure by pulling back the locks and lifting the handles on the cover.
09. Then, Marino disconnected the power feed wire.
10. With both handles pointing up, Marino lifted the cover, exposing the harness connectors.
11. Marino slid the connectors sideways to disengage them from the lower tray, and lifted the tray from the engine bay.
12. Meanwhile, Belcher accessed the spark plug wires by removing the coil covers and disconnecting the wires from the coils and plugs.
13. Belcher disconnected the steering shaft to gain a bit more room on the left side.
14. Next, Belcher and Marino removed the spark plugs.
15. Then, they detached the heat shields and removed the manifold bolts.
16. With the manifolds free, Marino gained the room necessary to remove the catalyst down pipes.
17. Then, Marino removed the OEM manifolds by tilting them back and snaking them out of the engine compartment.
18. With the OEM manifolds removed, we could compare them with the Hooker BlackHeart shorty headers. It’s easy to see why the Hooker shorty headers weigh 19 pounds less than the stock iron castings.
19. The Hooker BlackHeart shorty headers’ tubular design outflows the OEM manifolds.
20. The Hooker BlackHeart shorty headers feature a unique, 4-into-1 inline collector that’s carefully welded together by hand.
21. The inlet and outlet sides of the headers are hand-blended to maximize exhaust velocity and scavenging.
22. Belcher resumed the installation process by hoisting the Hooker BlackHeart shorty headers into place.
23. Marino reused the OEM gaskets and secured the headers to the cylinder heads using the supplied hardware.
24. Belcher installed the spark plugs and wires.
25. Marino reconnected the spark plug wires to the coils, and reinstalled the coil covers.
26. Marino and Belcher tag-teamed the job of securing the header collector flanges to the catalyst flanges.
27. Marino reinstalled the OEM mid-pipe, skidplate, chassis braces and oil lines.
28. Marino continued up top by reassembling the power distribution box.
29. Belcher filled the dry-sump tank with fresh oil. (Be sure to follow the OEM procedure, as it’s easy to overfill the system.)
30. With everything reconnected and complete, Belcher strapped the Z06 back on the dyno.
31. Without any other changes, the Z06 gained 11 rear-wheel horsepower at 5,200 rpm, and 14 lb-ft of torque at 4,300 rpm. We expect the gains to increase with further exhaust and other modifications.