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Ported Three-Valve 4.6 Cylinder Heads - Three's Company
Fox Lake Puts Its Magic Touch To A Set Of Three-Valve 4.6 Heads
Now that we've explored the majority of simple, bolt-on parts for the S197 Mustang, the next logical place to turn our collective attention is to the inner working of the engine. And, no matter how sophisticated or complicated an engine is, the true art of making power is getting more atmosphere stuffed into the combustion chamber. For decades, head porters have been enlarging the passageways and smoothing the aluminum of cylinder heads to hasten the trip from outside the air filter into the engine. Those artisans have always had the most influential role in helping hot-rod enthusiasts create more power.
It is no great surprise that Ron Robart, chief head porter and owner of Fox Lake Power Products, immediately went to work on the new Three-Valve heads. He had experimented extensively with the Three-Valve head in late 2003, when Ford launched the new F-150 powered by a modular engine carrying the same head design that would show up on the S197 Mustang in 2005. Those experimental attempts have paid off in spades, as Fox Lake has quickly jumped to the forefront of new Mustang-head modification.
We recently had a chance to follow along as our guys at MD Motorsports swapped out the stock heads of a customer's '05 Mustang with a set of Fox Lake CNC-ported Three-Valve heads. Reports of 20-35 rear-wheel-horsepower gains from test vehicles made us want to know firsthand what a head swap would do for the efficiency and power production of the newest small-block Ford.
Before we discuss flow numbers and what Fox Lake's mastery with porting tools will do for you, we need to examine the new head as it comes from Ford. Ron was enthusiastic about the basic design and engineering that went into the new Three-Valve head. Remember, when Ford went from the '04 Two-Valve to the '05 Three-Valve, it resulted in a 40hp jump in power. With all due respect to the variable cam timing and intake manifold, the new Three-Valve cylinder head is the primary reason.
"Ford drastically redesigned this cylinder head," Ron told us. "The Three-Valve head differs greatly from the Four-Valve head, and the most important part of that is the more vertical-straight up-angle of the intake port. It's going to make more power than the Four-Valve. Remember-when you bend air, it slows down. Ford straightened out that intake port, and it's a straight shot out the exhaust. You are going to make more power. It's not all in what you're going to see on the flow bench-that's just an indicator. This head flowing 270 cfm can make more power than a Four-Valve head flowing 300 cfm because the port is positioned better."
We told you he was enthusiastic. When looking at the Three-Valve head, remember that it's a mix of what we know about the two previous modular cylinder heads. That is, with two intake valves (twin 1.200-inch units), you have to compare it to a Four-Valve head, and with one exhaust valve (1.500-inch), you have to compare it to the Two-Valve. On the intake, the Three-Valve head has less cross-sectional area than a Four-Valve head, which should promote good velocity. And, as Ron points out, that intake port stands straight up, sucking the air right out of the intake with no bends to slow down this critical transition point. Ron compares this setup to a motorcycle head-a configuration that practically defines efficiency.
On the exhaust side, the Three-Valve head shines. "The bend of the port is a lot bigger than the Two- or Four-Valve," Ron beamed. "Just the design of the Three-Valve is going to let you make more power regardless of the flow number because the port has a better shape." Again, it looks as if the Ford engineers designed a straighter path out of the combustion chamber on the Three-Valve head, which greatly enhances exhaust scavenging and power.
To port this head, Fox Lake works to flow the most air without making the head too big (see Flow Bench Results for stock and ported flow numbers). For the application we are chronicling at MD Motorsports, it was critical not to "hog out" the head so that low-end torque would be diminished. With 99 percent of the applications, the ported stock heads will end up being down on torque if a porter gets too happy with the grinding tool. The flow numbers down low (in the 0.200- to 0.400-inch-lift range) are critical to good street performance.
"On this head, we focused on the lower-lift numbers," Ron explained. "It would probably flow 300 cfm if we made [the ports] bigger, but MD Motorsports wanted a good street head for its customer. For an average guy, this port job is big enough. The ports aren't so big that the engine will get 'boggy' down low. I designed these heads to have a nice, broad powerband for the Three-Valve engine. Justin Burcham at JPC has the exact same head, and he's going to make more than 700 rear-wheel horsepower. Obviously, if you are planning to put a blower on the car later, these heads can make big power."
Ron told us that as a general rule the larger the volume, or cross-sectional area, of the head, the more the power will be shifted from lower to higher in the rpm band. Again, the big ports are best left for the guys on the heads-up racing circuit who are banging shifts at 8,000 rpm.
Back to our Two-Valve/Four-Valve comparison-you can see the Three-Valve did 204 cfm at 0.600-inch lift. That's not as good as a Four-Valve (260 cfm), but it's killer for a Two-Valve head (180 cfm). Again, Ron has a race version of his CNC port for those customers looking to make tremendous power. The set of Three-Valve heads on his bench are flowing more than 300 cfm on the intake and 230 cfm on the exhaust at 0.600-inch lift-clearly, we haven't seen the end of head technology for this engine.
The Fox Lake Three-Valve head comes with a full CNC port of the intake and exhaust ports, as well as a hand-ported combustion chamber. Ron told us the new Three-Valve head is extremely sensitive to combustion-chamber porting-if you go too far, you can dramatically and drastically affect the quench area. Taking away too much quench area can result in a loss of good combustion properties of the head when the piston comes to top-dead center.
When Ron gets a set of heads, they are disassembled, CNC-ported, and hand-finished if necessary. The surfaces are milled perfectly flat, bronze valveguides and the appropriate valves are installed, then they are reassembled and shipped to the customer. As presented here, these Fox Lake heads feature Ferrea valves, springs, locks, retainers, the CNC port job, and hand-combustion-chamber finishing. Fully assembled, they ship for $1,400, plus core. Ron also has a set of heads that feature Manley valves, springs, stock locks, and stock retainers. These go out the door for $1,050.
At MD Motorsports-the Cincinnati-based powerhouse that has extensive experience in building, modifying, and tuning hot Three-Valve S197 Mustangs-we got a good look at what's involved in the head-swap process. Other than a shortage of Three-Valve head gaskets, our installation went seamlessly, with Brandon Alsept turning the wrenches and Ken Bjonnes doing the tune. Brandon estimates that a head swap at MD Motorsports would run around $850 in labor with an additional $200 in gaskets, fluids, and other miscellaneous parts. Brandon had about 10 hours in the head swap from start to ready to run out the door. Check out the accompanying photographs for a play-by-play.
Our test car came equipped with a set of stock headers, a Bassani X-pipe with cats, and a JBA axle-back exhaust. It also had underdrive pulleys and CMRC-delete plates. As such, it baselined with peak numbers at 288 hp and 303 lb-ft of torque at the wheels. With the Fox Lake Power Products CNC-ported Three-Valve head in place, the car picked up to 315.71 hp and 321.53 lb-ft for a sweet 28hp and 6-lb-ft gain. Most impressive was that this modification didn't kill the low-rpm torque you often find with other naturally aspirated modular engines that are equipped with good heads on a naturally aspirated combination. Ron's strategy to focus on air velocity-not overt flow numbers-helped maintain the engine's good street manners. This is often referred to as "area under the curve," and this port job kept the characteristics of the Ford design intact, while enhancing the good attributes.
In addition, the heads help extend the usable rpm of the engine with good rear-wheel-horsepower and rear-wheel torque numbers beyond those peak numbers. Instead of nosing over at 6,000 rpm, this engine-with the improved breathing of the Fox Lake heads-keeps going for another 1,000 rpm. That extended rpm range is something we'd like to explore when aftermarket camshafts for the Three-Valve heads begin hitting the market. Look for new camshafts and at least two intake manifolds soon, as new S197 Mustang modifications are coming out daily.
We had good peak power gains, but we were impressed that Fox Lake didn't kill the low-end power in the engine by going too big with the heads. Ron Robart's dedication to improved air velocity-not just flow numbers-shows here. You can also see this engine doesn't lie down like the stock one at around 6,000 rpm. It just keeps on going. A set of cams would be fun to try with these heads.
Part of extracting maximum power from any engine is finding where the restrictions are in the pathway of air through that engine. As part of our experiment with the Fox Lake heads, we continued the testing to see what kind of restriction the exhaust created once the heads were upgraded. Our test car had a set of stock headers, a Bassani X-pipe with cats, and a JBA axle-back exhaust. It also had underdrive pulleys and CMRC-delete plates.
The new exhaust consists of MD Motorsports-spec Kooks headers for the '05-up Mustang. They retail for $1,295 and, according to Brandon, the installation of these headers was the easiest they've performed on any modular Mustang. He did the swap in a rather quick six hours, and the labor costs for such a job would be in the $500 range. On the dyno, the car went from 315.71 hp and 321.53 lb-ft of torque to 328.02 hp and 329.31 lb-ft. With gains of 13 hp and 8 lb-ft, it shows there are some impressive gains to be made with a better exhaust. These are promising results, but the whole story won't be told until we get a good aftermarket intake for the Three-Valve engine to open up that end of the air path.