51hp Head Swap To the Wheels

If you've been keeping up with us on a monthly basis, then you'll surely recognize our '89 Mustang project mule from last month's test of the new Nitrous Express NXL system. While we proved that nitrous is the great equalizer for underpowered V-8s, we also learned that regardless of the number of bolt-ons you have, you're only going to make as much power as the most restrictive part of your engine combination will allow.

Twisted Wedge Flow Chart Lift Value Intake Flow (cfm) Exhaust Flow (cfm) 0.{{{100}}} 63 53 0.{{{200}}} 141 107 0.{{{300}}} 205 144 0.400 233 171 0.500 251 187 0.{{{600}}} 251 193 Note: Peak of a stock E7TE head is about 150 cfm @ 0.500 (int.) and 113 cfm @ 0.500 (exh.).

Case in point, our Mustang's 5.0L V-8 had been previously outfitted with a ported Ford Racing Performance Parts (FRPP) Cobra upper manifold, a larger 65mm throttle body, a massive Granatelli 80mm mass-airflow sensor, a Crane Cams 2040 emissions-legal cam (220/220 duration at 0.050, 0.498/0.498-inch intake/exhaust lift), and FRPP 15/8-inch shorty headers along with a complete 21/2-inch exhaust system. But it was all pumping through a restrictive set of factory E7TE cast-iron heads with 1.72/1.46 intake/exhaust valves.

Peak Dyno Numbers hp lb-ft Change Baseline 213 263 n/a TFS Twisted Wedge 264 307.5 +51/+44.5

We knew we had the potential to make a decent amount of power with the listed aftermarket goodies, and our baseline chassis dyno numbers revealed a respectable 212 hp with only 265 lb-ft of torque at the rear tires. Would a simple head swap be the final step that would turn this mild 302 into a robust boulevard brawler? There was only one way to find out.

Track Results Density Altitude 60-ft 1/4 e.t. 1/4 mph change Stock heads 200 feet 2.5 15.8 95 n/a TFS Twisted Wedge and Nitto NT-555R Extreme Drag Radial 3,432 feet* 2.1 14.2 99 -1.6/+4 *Tested at Los Angeles Country Raceway, corrects to 13.6 at 102 mph at sea level.

We paid a visit to the performance tuners at X2C Motorsports in Van Nuys, California, to began our experiment. Our heads of choice were a pair of out-of-the-box aluminum Trick Flow Specialties Twisted Wedge assemblies featuring 2.02/1.60-inch intake/exhaust valves with 61cc combustion chambers. The Twisted Wedge heads maintain the engine's stock 9.2:1 compression ratio, retain all the OEM-type accessory holes, and are a 50-state emissions-legal high-performance replacement for '88-'93 5.0L Mustangs. That means it'll get by the smog police with a very big Green Peace-style thumbs up. The bolt-on was simple, and we're happy to say the performance difference was staggering with a gain of more than 50 rear-wheel horsepower. Our little 302 now produces enough grunt to get us into trouble with the local authorities. Read on for the juicy details!