Richard Holdener
July 14, 2010

Once we had the baseline numbers, it was time for the head swap. Off came the stockers and on went the aluminum Brodix 195 castings. From a weight standpoint, aluminum heads have it all over their iron counterparts. That the Brodix heads also offered 195cc intake ports that flowed 300 cfm at 0.700-inch lift was icing on the cake. The Brodix heads also feature CNC-porting, the aforementioned 17-degree valve angle, and ductile iron seats for use with unleaded fuel.

Like the stockers, the Brodix heads were drilled for accessories holes so they can be run with A/C and power steering. The CNC-ported Brodix heads also feature 60cc combustion chambers, a 2.02/1.60 stainless steel valve package, and competition valve job. In short, the Brodix heads were everything the stock heads weren't. The only change required for the swap was replacing the stock 6.25-inch pushrods with a slightly longer 6.50-inch set from Comp Cams. We also replaced the self-guided rockers with Ultra Pro Magnum rockers from Comp Cams (retaining the 1.6 ratio).

After installation, the 347 came alive. The Brodix heads were run with the same dual-plane intake and Holley carb employed with the stock heads. No longer did the 347 struggle to produce 400 lb-ft of torque. In fact, the Brodix 195 heads transformed the 347 into a serious street/strip performer.

The power output jumped from 351 hp and 395 lb-ft of torque to 462 hp at 6,200 rpm and 435 lb-ft of torque at 4,400 rpm. The simple head swap improved peak power output by over 110 hp, but the gains were even greater higher in the rev range, where the power curve fell off dramatically with the stock heads.

Whereas torque production with the stock heads failed to reach 400 lb-ft, the 347 exceeded 400 from 3,500 rpm to 6,000 rpm. Don't be tempted to think the stock heads offered better low-speed power, as the Brodix heads improved the power output from as low as 3,000 rpm (our lowest test speed) to 6,800. The Brodix head swap improved the specific output of our test motor from a touch over 1 hp per cubic inch to a more street-worthy 1.33 hp per cubic inch. Add to that the significant reduction in curb weight and you have the reason why performance aluminum head upgrades are so popular on 5.0L motors.

It came as no surprise that the Brodix KC LH17 heads offered huge power gains over the wimpy factory heads, but we weren't finished with our Brodix-headed 347 test mule.

Since we had it on the dyno, we decided to swap out the dual-plane for a single-plane design. The funnel-web intake has always proven powerful, and this design is now available from ProComp as well. The only downside is possible hood clearance, as the high-rise intake will not fit under a stock 5.0L hood. Since our motor was not hood-clearance challenged, we opted to install the FunnelWeb intake on our 347.

The intake proved to be every bit as deadly as its eight-legged namesake, as power increased to an even 500 hp at 6,600 rpm. The peak torque was up slightly, to 441 lb-ft, but at a much higher 5,300 rpm. As expected, the single-plane traded a loss in low-rpm torque for all that wonderful top-end power. The dual-plane intake offered more torque and horsepower up to 4,800 rpm, but then it was all FunnelWeb up to our self-imposed ceiling of 6,800 rpm. The extra 40 hp offered by the FunnelWeb is certainly a compelling argument for a cowl hood!

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