Michael Galimi
March 11, 2011

For the past eight months, we've been following the latest go-fast goodies for the Coyote 5.0L-powered Mustang. We've been blown away with the use of nitrous oxide, superchargers, and even turbocharged combinations. In that time it seems as if MM&FF has covered dozens of bolt-ons, experimental parts, and power adders of all flavors from a wide variety of manufacturers. Each time we walk away more impressed with the gains and performance.

The moment has finally come for us to remove the cam covers and get to the juicy stuff. With that, we follow along as JPC Racing adds a set of its CNC-ported heads to Joe Marini's naturally-aspirated 2011 Mustang GT. Adding a power adder was out of the question for Joe, and so this is next logical step in his quest for power.

Marini's '11 Mustang GT is a veteran of the MM&FF 5.0L Shootout that was run in the Feb. '11 issue. It features all the latest and greatest parts like Kooks 1 3/4-inch, long-tube headers and 3-inch, X-style midpipe, 3-inch MagnaFlow after-cat exhaust, JLT cold-air kit, and custom JPC tune (DiabloSport Trinity). The suspension is hooked up for drag racing and the car has run 11.19 at 119 mph. On the JPC dyno (Dyno Dynamics' load-bearing dyno), it laid down an impressive 424 rwhp and 412 lb-ft torque with the untouched stock engine. Our task was to swap over to the JPC CNC-ported heads and chart the gains.

This CNC-porting job is a JPC exclusive designed by Rich Groh Racing (RGR)-a shop that isn't a stranger to horsepower, as evidenced by the nearly dozen NMRA championship victories credited to its engines. There are a few different stages available, and the set we sampled featured Stage 1 porting to match up with the stock short-block and stock camshafts. Stage 1 features opened intake and exhaust ports, five-angle valve job, and shimmed valvesprings. This stage utilizes the stock valves (37mm intake and 31mm exhaust), springs, locks, and retainers. Stage 1 heads go for $1,495 with core exchange, and RGR is currently working on Stages 2 and 3, which will include bronze valveguides, larger valves, and upgraded springs. Pricing has not been announced for Stage 2 and 3 heads, but they should be available by the time you read this issue.

JPC's Brian Clauss and Wayne Bryant were able to swap the heads without removing the engine. The spacious engine compartment of the S197 Mustang (released in 2005) is a distinct advantage over the previous generations. Long-tube headers and other bulky aftermarket parts just seem to be easier to install on the Three-Valve mod motor and the current Coyote 5.0L than previous Two-Valve and Four-Valve-equipped engines. We'd call this swap a two-day (or less) ordeal if you have mechanical experience. The chains are similar to the earlier mod motors in that you have to line up markings in order to keep the timing correct. At the time of our head swap, aftermarket bolt and stud kits for the Coyote were not available. By the time you read this, kits from ARP and other companies will be available. We used a set of Cometic multi-layer head gaskets that were just released at SEMA, as well as a pair of its exhaust gaskets.

So what's it worth? The quick answer is the CNC-ported heads brought peak numbers to 446 rwhp and 422 lb-ft torque. That's 22 rwhp and 10 lb-ft torque gain over the slightly modded but mostly stock engine. This is about what a typical head swap yields on a Three-Valve engine.

But the story goes much deeper than the just peak gains with the JPC heads. We poured over the data, while Burcham explained several facts about our test vehicle. The peak rwhp with the stock heads was 422 at roughly 6,400 rpm; on track, the car runs quickest when it's shifted at 7,400 rpm. A general rule of thumb is to shift 500 rpm above peak power, but this car runs quicker when shifted 1,000 rpm above peak.

"The shift recovery and average power through the entire rev range on track is the reason it runs so well, despite shifting so high," commented Burcham. He reports the car pulls strong to that rpm without dropping off. Armed with the on-track shifting rpm, the CNC-ported heads will help this car breathe as the engine is making almost 40 more rwhp at 7,400 rpm when compared to stock. The curve is more aggressive, which is going to lead to even quicker times.

We are disappointed that these heads weren't available when the weather was warmer (at least in the North) and the tracks in the Northeast were open. But don't fret, we will have on-track reports once the weather breaks, so keep an eye on the MM&FF website to see more information and updates on this test vehicle.

By the Numbers

Flow Testing JPC Racing Stage 1
CNC-ported Coyote 5.0L Heads
Lift IntakeCFM JPCCFM Stock
0.1005449
0.200197180
0.300266243
0.400303280
0.500321289
0.600335298
ExhaustJPCStock
0.1003732
0.200158147
0.300201180
0.400213189
0.500224201
0.600232207

Notes: All cylinder head flow testing was performed with a 92.2mm (3.63-inch) bore, which is the stock Coyote 5.0L bore size. RGR utilizes a Super-Flow 600 flow bench, 28 inches of water, and the exhaust ports were measured using a 1 3/4-inch pipe.

Photo Gallery

View Photo Gallery