Dr Jamie Meyer
March 19, 2010

Horse Sense:
If you're thinking about adding an intake and cams to complement a set of Fox Lake CNC-ported modular heads, you're in luck. Fox Lake and Mod Max are teaming up to design their own intake casting, and cams are already available. Of course, the Bullitt intake will suffice while you wait for the trick stuff to get off the design table.

So, you have a '99-'02 Mus-tang GT, and it's fast. You can kick a Camaro's rump and still have enough left for any ricer dumb enough to mess with a pumped-up, small-block Ford. You've done the gears, the sticky tires, the pulleys, the exhaust, the cold-air kit-man, you have everything. The problem is, you've spent all your loot on bolt-on parts and entrance fees to the local Wednesday night drags. You don't have the scratch to do that street blower you want so bad, but you still want to go faster. So, you put some nitrous to the old girl, get a couple 11-second timeslips, and really start to impress your friends. But what now? Where do you up the ante on this nasty, little overhead-cam wonder? Don't worry, we've got you covered!

Fox Lake Power Products has expanded its menu of CNC-ported 5.0 and 5.8 pushrod heads (of all castings, varieties, and flavors) to include Ford's modular cylinder heads. As with all Ron Robart's cylinder heads, his CNC port job originates from his own hand-cut design. After months of experimentation with the '99-and-newer P.I. castings (see Head Name Games sidebar), Ron developed a port configuration that offered enhanced air speed and volume without killing power, especially in the lower lift numbers.

A look at the Go with the Flow sidebar shows the heads peak at 210-212 cfm at 0.500 inch lift. That's up from 160 cfm with a stock P.I. casting. The stainless valve combination will get you up to 225 cfm at 0.500 inch lift. As a side note, the head is done after 0.500 inch lift. No amount of modifications, as tested at the time of this writing, will get the head to work at higher lift numbers. Now, if you're a dedicated 5.0&SF reader, you're saying, "Wait a minute. Those are typical numbers that you would see from a set of iron GT-40 heads for a 5.0." Well, you're right-and wrong. The flow numbers are the same, but the castings with the modular motors are what make the difference.

As Ron puts it, "The small, 281ci motor is the major difference. What looks like a small amount of airflow is really a huge difference because of the proportional difference (in engine size)."

Ron also explained to us that the P.I. head is efficient because it's a better overall design. It has a better taper angle from the intake manifold face to the valve-throat area. It has a high-speed port designed to direct the air to the cylinder, while the valve stops the combustion from going backward through the intake. And the P.I. heads are taller than a typical pushrod head, allowing for a much more direct angle of intake-charge flow.

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"If you could make a pushrod head with a design like this," Ron says, "you'd make a lot of power. With a pushrod engine, you've got the pushrods themselves and spring cups in the way of airflow. Any time that air has to bend, it slows down. These [modular] heads are really more like a motorcycle head. With the right cams and intake manifold, these things will rock to 9,000 rpm!"

OK, so the heads work, and Fox Lake makes them better. How much are they worth on your car? Fox Lake says independent testing with CNC-cut modular heads has shown a 35-rwhp increase with no other changes. However, if you have a good exhaust and a free-flowing intake (as we know you do), tests have shown a whopping 70-rwhp increase. Folks, that's like having a small hit of nitrous there all the time. Nice!

Our photos detail the work involved in what Fox Lake calls the Stage II port job. It includes the CNC port job, valve job, and flow test ($900). It's recommended that you get the bronze guides ($150). You will also be charged a cleaning and grinding fee ($48/pair), seats ($35), and assembly costs ($75). For a total of $1,208, Fox Lake has given the modular racer one more option when Second Place is not an option. Of course, you can add stainless steel valves ($289), while titanium retainers and spring kits ($270) for high-lift cams are also available. A Stage I porting ($599) provides some of the benefits at a lower cost.

Put some ported top-end parts together with a good selection of bolt-on speed parts, and you'll have one fast little Mustang. We hope you enjoy the extra kick in the pants.

Go with the Flow

LiftIntakeIntakeIntakeExhaustExhaustExhaust
Stock*Stage 1*Stage 2**Stock*Stage 1*Stage 2**
(inches)(cfm)(cfm)(cfm)(cfm)(cfm)(cfm)
0.100556061556064
0.20090100103869096
0.300130142151121127133
0.400142169179143150169
0.500150187205150164175
0.550161190220153172181

Measured at 28 inches of water
* Stock valves
** ModMax stainless valves, 0.050 inches larger than stock

After all the steps are carried out at Fox Lake, the flow numbers look like this. Every set of heads that go out the door has a flow sheet so the customer knows exactly what he's getting.

Head Name Games
One of the problems facing the modular Ford head porter is the great number of castings Ford has used on its modular engines. Most Mustang aficionados already know the '96-'98 heads are fairly down on power, and that the '99-'02 heads are the ones you want for anything more than a grocery getter. These are known as the "P.I." heads, which we're told stands for "Performance Improved." The P.I. heads come on Mustang GTs and 5.4 truck engines (hint to all those going through the junkyards looking for gold). As cast, the P.I. heads will greatly out-performance a production, passenger-car 4.6 modular head. However, something interesting happens when Ron CNC-cuts his handcrafted ports into a 4.6 head (of any '99-'02 casting)-the heads flow the same. There may be other variations in the head castings that we aren't aware of since the cutting of modular heads is still quite a young science. But Fox Lake looks to have the early jump on making your two-cam Mustang sit up and beg.