K-Manifolds
When we compare these numbers with the baseline figures, there's no gain in horsepower and just a single lb-ft of torque. Since we know from experience the K-manifolds do produce some power, we can only conclude that our 2-inch tubing and quiet passenger-car mufflers are holding things back.
| RPM | HP | TQ |
| 3,000 | 126.7 | 221.8 |
| 3,200 | 136.9 | 224.7 |
| 3,400 | 147.4 | 227.7 |
| 3,600 | 156.1 | 227.7 |
| 3,800 | 163.2 | 225.6 |
| 4,000 | 169.2 | 222.5 |
| 4,200 | 174.1 | 217.7 |
| 4,400 | 178.2 | 212.7 |
| 4,600 | 180.9 | 202.2 |
| 4,800 | 179.7 | 196.6 |
Full-Length Headers
With the full-length headers in place, the numbers were as follows:
| RPM | HP | TQ |
| 3,000 | 133.8 | 234.3 |
| 3,200 | 145.3 | 238.5 |
| 3,400 | 155.5 | 240.3 |
| 3,600 | 165.4 | 241.3 |
| 3,800 | 173.4 | 239.7 |
| 4,000 | 179.0 | 235.0 |
| 4,200 | 183.8 | 229.9 |
| 4,400 | 187.5 | 223.8 |
| 4,600 | 190.6 | 217.6 |
| 4,800 | 190.8 | 208.8 |
 The next exhaust test we have...  The next exhaust test we have planned for our '67 Mustang are these Hedman headers (PN 88300). They're a bargain at $134.88 per set. We had them left over from a different project we'd been working on. These headers fit only automatic-transmission cars. |  Here's our '67 Mustang fastback...  Here's our '67 Mustang fastback on the Dynojet rollers at Superior Automotive during the baseline tests. The car has a replacement 302 and an AOD four-speed automatic transmission. The engine is equipped with the standard log-type exhaust manifolds found on both A- and C-code Mustangs. Two-inch pipe runs from the manifolds back to generic passenger-car mufflers that are very quiet. |  Although they're available...  Although they're available from several different sources, this bracket comes from Hedman as PN 20120 and is $19.69. It's a must-have item for putting long-tube headers onto a car with power steering. The bracket allows the anchored end of power-steering ram to be lowered, creating clearance for the headers. |