Mustang Performance - Plan For Ponies, Part IV

Installing a Pertronix Ignitor...        read full caption Installing a Pertronix Ignitor retrofit improved reliability and idle quality. It also gave us a nice 2.7hp gain.

Removing the air cleaner to...        read full caption Removing the air cleaner to gain power is a legitimate myth. We gained 4.1 hp, but we lost torque. Despite the modest gain in power, we prefer to run the engine with its air cleaner installed.

Hedman headers did a lot for...        read full caption Hedman headers did a lot for performance in Part III. We tested them while capped and uncapped. Hint: You lose torque with open headers.

Part IV calls for the installation...        read full caption Part IV calls for the installation of Edelbrock Performer RPM aluminum cylinder heads with 1.94-inch Chevrolet intake valves.

These are nice heads because...        read full caption These are nice heads because they improve airflow, reduce weight, and allow more aggressive spark curves without detonation.

Screw-in rocker arm studs...        read full caption Screw-in rocker arm studs with pushrod guideplates infuse integrity into the valvetrain.

Tim Wedgeworth of West Coast...        read full caption Tim Wedgeworth of West Coast Classic Mustang shows us how simple the installation is because the Edelbrock Performer RPM is much lighter than the factory cast-iron head. Don’t forget the Edelbrock bolt spacers. Torque the heads to factory specs, just as you would iron heads.

Larger intake ports in the...        read full caption Larger intake ports in the Performer RPM heads become quite apparent here, because these guys fill the intake manifold gasket passages. It means greater torque and horsepower readings for your 289/302.

Because the Performer RPM...        read full caption Because the Performer RPM head is designed to fit both the 289/302 and the 351W, special bolt spacers have to be used with the 289/302 head bolts. Because the 289/302 block uses a smaller diameter cylinder head bolt than the 351W, the spacer takes up the space left by the smaller head bolt. These spacers are available from your local speed shop or Performance Automotive Warehouse (PAW).

Derek Real of Mike Morgan...        read full caption Derek Real of Mike Morgan Motorsports evaluates the 14th dyno run to see what Edelbrock Performer RPM heads did for performance. When you compile all the performance upgrades we’ve completed to date, it amounts to nearly 50 hp, thanks to Edelbrock, Hedman, Comp Cams, and National Parts Depot. Next month, we’ll swap the camshaft.

Usable real-world power does not come easy. West Coast Classic Mustang’s Jerry Choate provided us with his father-in-law’s dead stock ’65 Mustang GT hardtop as a test mule for our effort. We drove it across Southern California’s San Fernando Valley to Mike Morgan Motorsports in Burbank for a quick analysis of how much power an aging stock Mustang could produce. Derek Real of Mike Morgan Motorsports pulled the Mustang onto the chassis dyno on a hot day for that first pass in stone stock condition right off the street—untouched: horsepower was 128.4 at 4,100 rpm and torque peaked at 193.9 lb-ft at 3,400 rpm.

We popped the hood for a closer look. For starters, the vacuum advance wasn’t working—thereby causing a lapse in power. Stock ignition points and condenser were marginal at best. We installed a Pertronix Ignitor, which netted 2.7 hp and 1.1 lb-ft of torque. This told us that the Ignitor is more about reliability and smooth performance than power. Idle quality improved with the Ignitor as well.

After we installed the Ignitor, we removed the air cleaner for a modest increase in horsepower and a slight loss of torque. Fresh spark plugs made very little difference in performance.

When West Coast Classic Mustang installed the Edelbrock Performer RPM intake manifold and carburetor in Part II, we expected an obvious increase in power—but that’s not what we received. We actually lost torque and noted a modest increase in horsepower. Derek Real super-tuned our 289 for modest gains in horsepower and torque. We gained a total of 16.3 hp and 7.4 lb-ft of torque with super-tuning and an induction swap; however, adjustments in spark timing and changes in carb jetting didn’t do much for performance. Not bad, but nothing to go bench racing with either.

When we installed Hedman headers and the Turbo 2-¼-inch exhaust system from National Parts Depot in Part III, we witnessed increases in power—especially with more super-tuning from Mike Morgan Motorsports. With a fresh exhaust system and carburetor tuning, power jumped to 224.7 lb-ft and 158.5 hp at the rear wheels. Just for fun, we uncapped the headers and let the Mustang scream with a loss in torque yet an increase in horsepower. The exhaust-system back pressure gives us torque, especially when valve overlap is optimum. So uncapping the headers isn’t always going to help you at the dragstrip. In fact, it can hurt you out of the hole.

This leads us to the entire point of our power lecture. In order to generate real power, you have to modify your engine as a package—not piecemeal. Tuning and a better ignition system netted modest increases in power. An Edelbrock intake and carb bumped the power considerably. But our 289 didn’t really wake up until we rounded out the package with Edelbrock Performer RPM cylinder heads. Performer RPM aluminum cylinder heads sport larger-than-stock valves and ports. What’s more, the port design is cleaner. Aluminum heads help eliminate combustion heat, enabling us to advance spark timing without the risk of detonation and engine damage.

West Coast Classic Mustang removed the stock 289 4V heads and installed the Edelbrock pieces fitted with Comp Cams’ roller rockers and pushrods. The dyno readings show how Part IV played out.

As you can see by examining the readings, a head swap does a lot for horsepower. Horsepower is up 17.8, and torque is up 6.3 lb-ft. We’re convinced that this engine would create even more horsepower if pushed beyond 5,000 rpm. Because the engine’s structural integrity is unknown, we’ve kept it conservative. We’re more interested in the overall gains throughout our test. Since our baseline test, we’ve gained 37.1 lb-ft of torque and 47.9 hp. Call this an easy 50hp gain at the drive wheels—with aftermarket heads, an intake manifold, a 600-cfm carburetor, Hedman headers, National Parts Depot’s Turbo 2-¼-inch dual exhaust system, and super-tuning by Mike Morgan Motorsports.

So what does this tell us about aftermarket parts? It tells us that we should think of our modifications as a package for best results, then enjoy the benefits of power when the job is finished. In the final installment, we will round out this package with a more aggressive hydraulic camshaft from Edelbrock, along with one last trip to the dyno for good measure.