Loyal Car Crafters will remember that our 5.0L Fistfight adventure started back when we compared the 5.0L Ford against the LB9 305 TPI Chevy in stock trim. The Chevy won round one thanks primarily to the condition of the two test engines. The TPI 305 was basically brand spanking new, while the used Ford, an LKQ Pick-Your-Part special, had previously logged 150,000 miles, and possibly more than that. In round two, we subjected the dynamic duo to the usual array of fuel-injected modifications, including heads, cam and intake. The 5.0L Ford received Trick Flow Specialties' Twisted-Wedge heads, a Comp XE274HR cam and TFS' Track Heat intake system. The Chevy received similar components, including Trick Flow's Super 23 heads (designed for the small-bore 305), a Comp XR276HR cam, and Holley's Stealth Ram EFI intake. When the dyno smoke cleared, the 5.0L Ford won round 2, but only by the smallest of margins. Here in round three, we decided to ditch the fuel injection in favor of carburetion then add a little shot of nitrous. Keyboards at the ready Chevy guys? The Ford also received new cylinder heads, but more on that later.

In preparation for the next dyno session, the 5.0L Ford was stripped down to the short block, and the new TFS 11R heads were installed using fresh Fel Pro 1011-2 head gaskets and ARP head bolts. Once again, we relied on the TFS 1.6-ratio, aluminum roller rockers and hardened pushrods. We retained the Comp XE274HR camshaft from the previous test, as there was limited piston-to-valve clearance with the factory pistons. Topping the 11R heads was a single-plane, Funnel Web intake from Speedmaster. The high-rise, Funnel Web featured lengthy, straight-shot runners to the head ports designed to maximize power production over a broader range than a typical single plane. To that, we added a Holley 650 XP carburetor, an MSD distributor, and Hooker headers for this carbureted combination. Equipped as such, the 302 produced 415 hp at 6,500 rpm and 369 lb-ft of torque at 5,600 rpm. That represented a significant jump in power compared to the EFI combination with the standard Twisted Wedge heads.

Now it was time for the Chevy to strut its stuff. Unfortunately, the Chevy did not receive a cylinder head upgrade. While Chevy guys may call foul, the reality is that the larger bore on Ford's 302 allowed it to run any of the 30 different cylinder heads currently available. By contrast, the 3.736-inch bore 305 is limited to just a handful of cylinder heads available in the aftermarket- the best option being the Super 23 heads previously installed. Since TFS did not offer a ported version of these heads, we elected not to treat them to custom porting, though this would be an option for a diehard 305 owner. The better choice would be to build a 4.0-inch bore 302 Chevy or just step up to the larger 350 and be done with it. If you elect to stick with the 305, know there are limitations.

For this test, our 305 received a single-plane, Victor Jr. intake (one previously converted for EFI use). This necessitated the use of a 2-inch, Wilson tapered-combo spacer to clear the fuel rail. Run with the same 650 XP carb, the 305 Chevy produced 376 hp at 6,100 rpm and 343 lb-ft of torque at 4,600 rpm. Now that we have suitably alienated the Chevy contingent, here is how we leveled the playing field: enter nitrous oxide.

Not content to just run our dynamic duo with carburetion, we decided they both needed power adders, so we set up each one up with a Zex Perimeter Plate nitrous system. The same plate was used for each engine and equipped with jetting to provide an additional 100 hp at the push of a button. For the Chevy guys, we put a little extra time in to dial in the tune and managed to close the gap considerably on the Ford. Run on the Ford, the Zex Perimeter Plate increased the power output of the carbureted combo exactly 100 hp, with a peak of 515 hp at 6,500 rpm and 486 lb-ft of torque at 5,400 rpm. The torque was more a function of how early we engaged the nitrous: the lower the engagement, the higher the torque number. Running the same jetting on the Chevy (with 2 degrees more timing and a slightly leaner mixture than the Ford), the Chevy posted peak numbers of 505 hp at 5,600 rpm and 488 lb-ft at 5,400 rpm. So what is next for our little 5.0Ls? Boost baby, boost!

Graph 1:

Carbureted 5.0 Ford: N/A vs Zex

Run with the TFS 11R heads and Speedmaster Funnel-Web intake, the carbureted Ford produced 415 hp and 365 lb-ft of torque. After adding the Zex Perimeter plate nitrous system, the peak power output jumped to 515 hp. The Zex Perimeter Plate was set up with jetting to provide an extra 100 hp, and that is exactly what it did. It is amazing how easy it was to add power with the Zex system.

Graph 2:

Carbureted 305 Chevy: N/A vs Zex

The modifications to the TPI 305 were less elaborate. The Chevy received an Edelbrock Victor Jr. intake, Wilson carb spacer and the same Holley 650 XP carb run on the Ford. Run in this configuration, the little Chevy produced 376 hp at 6,100 rpm and 343 lb-ft of torque at 4,600 rpm. These numbers jumped to an impressive 505 hp once we added the Zex nitrous. We got a little more aggressive on the tune with the Chevy to help make up for the 11R heads on the Ford, but we now have a pair of 5.0Ls each making over 500 hp. I guess the only thing left is boost!

See all 19 photos

See all 19 photos In our last installment (pt 2), we subjected the 5.0L Ford to upgrades that included Trick Flow Specialties' Twisted Wedge heads, a Track Heat intake, and a Comp XE274HR cam. The combination produced 376 hp at 6,000 rpm and 355 lb-ft of torque at 5,300 rpm.

See all 19 photos The Chevy received a similar treatment, with TFS Super 23 heads, a Comp XR276HR cam and Holley Stealth Ram intake. The little TPI Chevy produced 370 hp at 6,100 rpm and 349 lb-ft of torque at 4,800 rpm.

See all 19 photos In preparation for the new mods, the Ford was once again stripped down to the short block, but we retained Comp's XE274HR cam.

See all 19 photos TFS offered up a set of their new CNC-ported, 11R 170 cylinder heads, which are fully ported and feature revised valve angles and a spring package that allowed our hydraulic roller cam to rev cleanly to 7,000 rpm.

See all 19 photos We installed the heads onto the awaiting 5.0L Ford short block using Fel Pro 1011-2 head gaskets and ARP head bolts.

See all 19 photos The TFS 11R heads were topped with a single-plane, Funnel Web intake from Speedmaster.

See all 19 photos Feeding the new intake and cylinder heads was a Holley 650 XP carburetor.

See all 19 photos Both the Ford and Chevy relied on MSD billet distributors and a 6AL ignition amplifier.

See all 19 photos With this setup, the 302 produced 415 hp at 6,500 rpm and 365 lb-ft of torque at 5,600 rpm.

See all 19 photos Lacking available heads for the small-bore 305, we simply installed an Edelbrock Victor Jr. intake. This intake had previously been modified (externally only) to accept fuel injectors, but we ran it in carbureted trim.

See all 19 photos The position of the injectors required us to run a 2-inch Wilson tapered-combo spacer to clear the throttle linkage. We relied on the same 650 XP Holley carburetor on the 305 Chevy.

See all 19 photos Run on the dyno with the carbureted induction system, the little 305 Chevy produced 376 hp at 6,100 rpm and 343 lb-ft of torque at 4,600 rpm.

See all 19 photos Next up, we installed a Zex Perimeter Plate nitrous system on each engine, starting with the Ford.

See all 19 photos Run with 100-hp jetting, the Zex kit provided exactly that on the Ford, upping the peak power output to 515 hp at 6,500 rpm.

See all 19 photos The Chevy got the same treatment, with installation of the Zex plate on the Wilson carb spacer.

See all 19 photos A little more aggressive tune on the Chevy nearly made up for the ported heads, as the Zex kit increased the power output of the 305 to 505 hp.