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Horse Sense: Before we go forward with this report, let's backtrack for those of you not sure what we mean when we refer to the Three-Valve powerplant. We understand that all of our readers aren't Melvins when it comes to technical knowledge about Mustangs, and there are folks out there who hear the term all the time but just don't know what it means. The new-Mustang engine's Three-Valve moniker is derived from the addition of a second intake valve in the cylinder heads. Basically, the extra valve per cylinder allows more air to fill each hole, which in turn enables the '05-'09 4.6 engine to make more horsepower than its Two-Valve (one intake/one exhaust valve per cylinder) predecessor, which was found under the hoods of '99-'04 Ponies.
As living, breathing creatures, we all depend on air in some way, shape, or form. As gearheads, we understand that although engines are mechanical, they also rely on air for the same reason--it enables them to function.
Air and "breathing" are just as critical for engines (especially the force-induced Three-Valve engines we're seeing a lot more of in modified '05-'09 'Stangs) as they are for all of us. Since new technology for tres-valve modulars hits our radar with the same almost-daily frequency that the Fox gear did years ago, we've been keeping a close eye on all of the upgrade induction pieces being developed to further enhance the performance potential of supercharged and turbocharged S197 GTs.
Johnny Morris spins wrenches and does all of the dyno tuning at Image One Motorsports in B
While S197 CAI systems, throttle bodies, ported cylinder heads, and even aggressive camshaft profiles have led the new-parts hit parade for a while, many aftermarket companies are now making steady inroads in their development of aluminum intake manifolds for Three-Valve engines. This definitely has us hyped. The news of aftermarket intake manifolds is important, because although the composite-plastic, variable-length intakes that Three-Valve engines are equipped with from Ford are good (capable of supporting as much as 500 rwhp in many cases), they tend to be restrictive and much less efficient in the higher-revving, bigger-horsepower turbo and blower applications that many 'Stangbangers are building for the street.
From a low-budget perspective, bolt-on pieces such as throttle-body spacers and delete plates for charge motion runner controls are available, and they do help improve high-rpm performance of stock intakes by smoothing out turbulence as air enters the manifold and travels through the intake path to the cylinder heads. However, as many of you know or are experiencing, it's a tough battle trying to maintain any true sense of low budget when your intent is to go far above and beyond the 460ish-horsepower capacity (with stock internals) of a Three-Valve engine.
Making big steam--horsepower far beyond the 550 ponies at the feet that these days seem to be, well, entry-level for modified 'Stangs--requires investing in a short-block (which in some case includes the engine block itself) outfitted with a forged crankshaft, rods, and pistons that are up to the task of performing consistently under severe-duty conditions. On the top side of said engine, pressurized airflow is best managed with a larger throttle body, camshafts with increased duration, ported heads, and an unrestrictive aluminum intake manifold. Focusing on the manifold for a second, the design and construction (material, runner shape/length, and so on) of the intake manifold probably is the most critical factor in an engine's overall volumetric efficiency.
Keith Logan and his son, Dwayne, of Logan Motorsports in Elgin, Illinois, think about VE all the time, including methods of manipulating it for improved performance from 4.6- and 5.4-liter Ford engines. Airflow, of course, is key, and the Logans have developed a series of absolutely gorgeous aluminum sheetmetal intake manifolds for Two-, Four-, and now Three-Valve bullets that help maximize airflow in these engines. ['Net surfers may have already seen KJ's sneak-preview photos of the Three-Valve intake that were posted in our website's blog section last June--Ed.].