Bolstering Our 1965 Mustang’s 289 Breathing Yields A Solid Gain

For those following along with the build of Chris Friend’s 289-powered 1965 Mustang project, you know we have upgraded the induction system with the addition of a Holley Sniper 2 fuel-injection system and supported that electronic upgrade with a more robust one-wire alternator from Powermaster. Those upgrades set the stage, adding more horsepower to the combination.

We wanted to wake up the 289-cube small-block under its hood with improved induction and a more aggressive camshaft. AFR’s Enforcer Top End Kit for small-block Fords brought those upgrades together in one cohesive package. This isn’t some piece-meal bolt-on combo; rather, it’s a complete package designed to deliver solid power gains while keeping things street-friendly.

To enhance the performance of our 1965 Mustang’s 289-cube small-block, we recently added a Holley Sniper 2 fuel-injection setup and a Powermaster one-wire alternator. To increase its performance, we selected AFR’s Enforcer Series Top End Kit for small-block Fords (P/N 3910-TEK: $2,883). This comprehensive system includes fully assembled Enforcer Series 185cc cylinder heads, a matching intake manifold, polished aluminum AFR valve covers, Fel-Pro gaskets, ARP head bolts, spark plugs, and more. (Photo Credit: Air Flow Research)

At the heart of this kit are the 185cc Enforcer heads with 64cc chambers. These bad boys are made with AFR’s permanent mold “as-cast” tech, which means the ports are super consistent and flow like mad right out of the box. They come fully loaded with all the good hardware as well, including PAC Racing valve springs, 2.02×1.60-inch stainless steel valves, and Viton seals. That’s all the gear you’d expect from quality, aftermarket heads, but ready to install without the headache of sourcing the individual components.

The Enforcer heads are designed for enthusiasts who want serious performance but don’t need full CNC porting. You get that great airflow right out of the box thanks to AFR’s casting technology, and everything fits perfectly on our 289. They deliver a solid bump in power while keeping things streetable.

To round out and freshen our combination, we turned to Engine Pro for a set of 6.9-inch (+.100-inch over stock) Nitro Black 5/16 SBF pushrods (P/N: 5116-6900), a set of Street Performance hydraulic-roller lifters (P/N: 17-5323-16), a Billet Double-Roller Timing Set (P/N: 08-2003T-9), a set of 3/8-inch aluminum 1.6:1 roller rocker arms (P/N: 07-1017-16), and a three-bolt harmonic balancer (P/N: PB1008-ST).

The intake manifold is another convenient piece of this package. It’s a low-profile single-plane design, built for 8.2-inch deck heights, so it fits tight and keeps our classic engine bay looking cohesive. A lot of enthusiasts want to keep the stock hood or at least avoid chopping it up, and that’s where the low-profile manifold shines. It’s designed to fit right in with the heads and keep everything compact, but you don’t have to compromise on performance for a clean installation.

We began by draining the coolant and plucking out the radiator, which gave us plenty of room to work. Then we removed the existing exhaust, intake, lifters, pushrods, cam, heads, timing cover, and crank damper to take the 289 down to its short-block.

Total Package

While the AFR Enforcer Top-End Kit is a well-matched package, we needed some other upgrades to maximize its potential on our 1965 Mustang’s vintage small-block, so we turned to Engine Pro for the rest of our upgrades. They included a set of 6.9-inch (+.100-inch over stock) Nitro Black 5/16 pushrods (P/N: 5116-6900), a set of Street Performance hydraulic-roller lifters (P/N: 17-5323-16), a Billet Double-Roller Timing Set (P/N: 08-2003T-9), a set of 3/8-inch aluminum 1.6:1 roller rocker arms (P/N: 07-1017-16), and a three-bolt harmonic balancer (P/N: PB1008-ST).

We also installed a prototype AFR Enforcer camshaft (P/N 6033) hydraulic-roller cam with .502-inch lift and 226 degrees of duration (@ .050) on the intake side and .511-inch lift and 232 degrees of duration (@ 0.50) on the exhaust side. It sports a streetable,110-degree lobe separation. Designed for carbureted small-blocks promises muscular midrange, which is ideal for street performance vehicles with 2,200-stall converters and 3.55 gears. AFR doesn’t yet offer camshafts as part of its Top-End Kits for the small-block Ford, but the company will do so in the future.

With all that gear in hand, we were ready to swap over our top-end components while moving to a more efficient, lower-maintenance roller camshaft, which did require changing from the stock 289 firing order to a 1-3-7-2-6-5-4-8 351W firing order.

Designed to flow more than 250 cfm on the intake side and 170 cfm on the exhaust side, the AFR 185cc Enforcer aluminum heads were engineered to outperform the stockers. Of course, being aluminum, these reduce the weight at the front of the car, and that 44.8-pound savings is evident by the car’s more agile handling after the upgrade.

Installing the kit is smooth sailing thanks to how well these parts play together. No hunting for bits and pieces or hoping they fit — AFR’s taken the guesswork out by ensuring everything works as a team.

One of the biggest selling points of this kit is that it’s a complete system. All the parts are designed to work together perfectly, so you avoid the headaches that come from mixing aftermarket parts that weren’t made for each other. That means the installation goes faster, and when you fire it up, you know it’s running the way AFR intended — optimized from the heads to the intake.

Our factory damper was well worn and devoid of markings, so we were thankful the new unit from Engine Pro was fully marked, which made setting up the engine timing a breeze.

We began the installation process by stripping the stock top end off, taking our time to clean all the sealing surfaces and prep the block. When it came time to bolt down those new heads, we followed a three-step torque process, tightening the bolts from the center out in a spiral to get an even seal. The intake got a careful layer of RTV on the gaskets to prevent leaks and was torqued down in a crisscross pattern to keep everything square. Pushrod length and valvetrain geometry got our full attention, making sure everything’s perfect for long-term reliability.

After cleaning all the surfaces, we got down to the job at hand by applying ample assembly lube to the prototype AFR hydraulic-roller camshaft before sliding it into place. After installing the cam, we bolted on the fresh billet, double-roller timing set from Engine Pro, and bolted on the new harmonic damper, which was also from Engine Pro.

Smooth Installation

Dialing in your pushrod length and checking rocker geometry is critical when you’re upgrading heads like this. If you skip this step, you risk premature wear or even damage to your valvetrain. The Enforcer heads come with guideplates and use 7/16-inch rocker studs, so it’s important to take your time here and get it right to ensure longevity and performance of your combo.

Once everything was buttoned up, we fired up the improved 289 — after reconfiguring the firing order in our Holley Sniper 2 EFI System — and that idle was crisp and mean. Then it was time for the dyno. The engine produced 231 horsepower and 228 lb-ft of torque at the rear wheels, which is significantly better than a stock 289, which might put down as little as 140 or as much as 180 horsepower at the wheels in factory form. With more tuning and rpm, we could have easily seen higher numbers. However, we didn’t just gain power, our ’65 Mustang is more responsive, quicker, and a heck of a lot more fun to drive.

These tie-bar-style hydraulic roller lifters from Engine Pro make quick work of a roller cam conversion, as they just drop right in. Be sure you order the proper-length pushrods for your combo as we did.

When you hit the gas on this setup, the sound tells you everything. Our 1965 Mustang isn’t just louder, it has a richer tone — that classic muscle car bark with a modern edge. It changes the character of the engine without making it feel wild or unruly. That’s what makes this kit so special for street guys who want that muscle car feel with daily drivability.

If you want to keep your classic Mustang’s vintage vibe but make it run like a modern muscle car, the AFR Enforcer Top End Kit is a comprehensive solution. It’s a well-engineered, bolt-on upgrade that gives you power, reliability, and that killer rumble without sweating any mismatched components.