"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
| Lift | Intake | Intake | Intake | Exhaust | Exhaust | Exhaust |
| Stock* | Stage 1* | Stage 2** | Stock* | Stage 1* | Stage 2** |
| (inches) | (cfm) | (cfm) | (cfm) | (cfm) | (cfm) | (cfm) |
| 0.100 | 55 | 60 | 61 | 55 | 60 | 64 |
| 0.200 | 90 | 100 | 103 | 86 | 90 | 96 |
| 0.300 | 130 | 142 | 151 | 121 | 127 | 133 |
| 0.400 | 142 | 169 | 179 | 143 | 150 | 169 |
| 0.500 | 150 | 187 | 205 | 150 | 164 | 175 |
| 0.550 | 161 | 190 | 220 | 153 | 172 | 181 |
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.