Ford 302 Engine Build Up - Modern Motivation

When it comes to carbureted small-block Fords, a few notable candidates quickly come to mind. The early 271-hp (high-performance) 289s are naturally high on this list. Their high-revving nature allowed them to creep very close to the then-magical number of 1 (gross) hp per cubic inch. When Carroll Shelby came along and turned his performance wizards loose on the little Ford motor, they managed to up the power number to an impressive 306 hp from the little 289. Stepping up in displacement to the slightly larger 302, there is but one high watermark-the big bad boss himself. Though rated by Ford at just 290 hp, the real output of the legendary Boss 302 was thought to be considerably higher by racers and other performance enthusiasts in the know. Equipped with the free-flowing Cleveland-style cylinder heads, the Boss 302 was the small-bock Mustang to own and continues to be sought after by true Blue Oval enthusiasts.

As great as those early performance motors were, they simply can't compete with what is available today. Remember, it has been more than 30 years since Ford introduced the Boss and even longer since the heyday of the Shelby GT350 Mustangs. Technology has marched on in the form of high-flow aluminum cylinder heads, powerful camshafts and even more efficient carburetors (to say nothing of fuel injection). Benefiting from this infusion of technology are Ford enthusiasts. What this means is that the average early Mustang owner no longer needs to long for the performance offered by a HiPo, Boss or Shelby. Instead, you can whip up a performance street 302 using a select few aftermarket parts that would literally run circles around the best small-block Ford ever offered. In fact, thanks to modern technology, you can build a daily driven street motor that will out-perform even the FIA race motors used in the legendary Cobra Daytonas! How's that for impressive?

The key to all of this usable performance is in what we refer to as the power producers, namely the camshaft, cylinder heads and induction system. The aftermarket has made great strides in the last 30 years, so it should come as no surprise that we are able to surpass the power levels of yesteryear. Where 1 hp per cubic inch was the holy grail of power output for the manufacturers, it is now commonplace, at least for any performance street motor. In fact, if you built a performance 302 that only made 302 peak hp, you should consider your project somewhat less than successful, unless your buildup was more of a rebuild using primarily stock components. That we can now build a 302 that exceeds the power output of the early performance (and even race) motors should not be surprising, but that it can be done so easily and with excellent street manners is all the more impressive. Not only can a 302 be built that exceeds 375 hp, but such a motor can also be built for use as a daily driver. Such a motor offers not only impressive peak power numbers, but also a broad power band (torque curve) and acceptable idle quality. After all, who wants a temperamental race motor while they are inching along in bumper-to-bumper traffic?

Building a successful performance street 302 requires a game plan. Before choosing the necessary components, you must first decide on the intended application. Will the motor be used primarily for street with an occasional trip to the strip, or will time slips rule the buildup? Your choices will be different depending on how you answered these questions, but we chose the milder route, with an emphasis on street. Though our emphasis was on drivability, we didn't want to undermine performance altogether. One criterion that always enters into the picture is cost. If cost is no object, it is much easier to achieve your goals. I don't know about the rest of you, but I have never had the opportunity to build a cost-is-no-object motor. Realizing that the majority of these motors are built by cost-is-definitely-an-object enthusiasts, we made every effort to keep costs down. The cost factor also eliminates any exotic parts that tend to reduce reliability right along with the size of your bank account. Trick, exotic hardware may impress the folks at the local drive-in (do they still have those anywhere?), but try getting a replacement at your local parts store. A true daily driver means something that can be repaired with a quick trip to the your neighborhood parts store.

In keeping with the driver theme, our buildup began life with a stock 5.0L 302 block. The stock (late 5.0L) 302 block had many desirably qualities, including being set up to accept a hydraulic roller cam and attending valvetrain. While early 5.0L blocks came equipped with forged pistons from the factory, we decided to upgrade the stock short-block with a set of rods and pistons from Coast High Performance. While the factory components are more than adequate for this power level, for rock-solid reliability we stepped up to forged aftermarket rods and pistons. We retained the cast crank, since we had no intention of running the motor much past 6,000 rpm (certainly not more than 6,500 rpm). Given the short stroke and strength of the internals, the 302 short-block should be able to run to 6,000 rpm almost indefinitely.

The Probe Racing forged pistons combine with our TFS Twisted Wedge heads to produce a street-friendly static compression ratio 9.2:1. The relatively low compression allows easy use of 91-octane premium unleaded for maximum performance but will likely tolerate all the way down to 87 octane (regular unleaded) for the daily commute. The near flat-top pistons help optimize flame travel (requiring less initial timing) while the aluminum heads help dissipate combustion heat to further suppress detonation. With the CHP 5.0L short-block providing a solid foundation, the key to the performance of this street 302 was in the induction system. The critical elements to power production are the cylinder heads, camshaft and intake system. It should be noted that similar results could be obtained by using an early hydraulic flat-tappet 302 block. The flat-tappet cam would also allow a few more revs before valve float, as the hydraulic roller valvetrain is considerably heavier than the early flat-tappet system.

It wasn't long ago that the only choice for cylinder heads was the factory offerings. In the old days, your choices for topping a 5.0L or early 302 basically consisted of stock (E7TE) 5.0L casting, early 289 HiPo heads or the cream-of-the-crop 351 Windsor heads. Actually, none of these offered much performance, at least not compared to anything currently available from the after market. Early Mustang owners should thank their lucky stars that the late-model 5.0Ls became so popular, as performance parts abound for Windsor-based Fords, including cylinder heads.