This mild-mannered Mustang...
This mild-mannered Mustang GT is now an 11-second street car thanks to the M2 ST 5.0R cylinder heads from Brodix. Note the white-knuckled driver attempting to harness 473 rwhp with 17-inch drag radials.
Before we get into the nuts and bolts of this tech article, we want to tell you about the events that led up to it, as they were primarily the driving force behind testing the Brodix cylinder heads in the first place. Oftentimes, tech stories are hatched within the confines of the top-secret editorial meetings at MM&FF Command Central. This story, on the other hand, was borne out of the need to send the nearest competitor packing.
The trash talking started in early summer as we recall. Associate Tech Editor John Hedenburg got the whole challenge rolling with Don King-like flair. Comments were fired from office to office, either by e-mail or verbally. "The preposterous power of the pony shall prevail in this perilous time," touted the big-wigged Hedenburg. Conversations at lunch and at editorial meetings did not go unscathed either, and dyno results were repeatedly posted on opponents' doors, as the scale of horsepower increased each week leading up to the track date.
You see, we share office space with GM High Tech Performance magazine and its editor Rick Jensen, who happens to own a hopped-up Buick Turbo T Regal, and Hedenburg had put our resident '90 supercharged Mustang GT up against said Buick in quarter-mile competition. Rick had already lost his first match race against our '99 Lightning project truck, alias The Fridge, a year earlier and was looking to repair his racing reputation.
The ST 5.0R cylinder heads...
The ST 5.0R cylinder heads with the M2 CNC porting have a street retail of about $1,999 assembled, but can be purchased as bare castings for those who plan to hog them out further, or just want to use their own valvetrain components.
His turbocharged six-cylinder had just received a new high-performance intercooler, a rebuilt transmission and a stall converter, and he hoped to improve on its best of 12.34 with those modifications. Rick also feeds the Buick a healthy diet of 116-octane race gas and some 24 psi of boost. Subsequently, it was up on the Mustang by about 10 hp and a stout 60 lb-ft of torque.
Our Fox GT, wearing 17-inch BFG drag radials and burning nothing but pump gas, was running stout 12.25s at 115 mph with its ProCharged 143,000-mile 302 motor; however, some unplanned drag passes at the MM&FF 2003 Two-Valve Shootout resulted in the coolant gushing out of the overflow tank. There had obviously been a breach in the high-mileage head gasket. That wouldn't have been a problem except for the Buick shootout was scheduled for the following week. It was decided that as long as the heads were coming off it would be a shame not to upgrade, and a few extra oats in the feed bag wouldn't hurt either.
Editor Campisano placed a call to the reigning engine dyno king of late-model Fords, our own Richard Holdener, who offered to next-day-air us a wicked set of M2 CNC-ported Brodix ST 5.0R cylinder heads. The aluminum Brodix units had produced a stout 434 hp and 410 lb-ft of torque on a carbureted 331ci motor (MM&FF, November 2003) so we knew there was plenty of potential. Holdener also supplied us with an E303 camshaft to make the most of the improved induction, but the combination of stock pistons and 2.02 intake valves left us with a mere .018-inch piston-to-valve clearance. This obviously would not play, so back in went the stock camshaft, .444-inch lift and all.
The ST 5.0R heads come with 171cc intake ports and 60cc chambers, but the M2 versions feature 2.02/1.6 valves versus the 1.94/1.6 arrangement, and the intake ports grow to 185 cc while the chamber volume rises to 66 cc (which was great for our supercharged application). According to Holdener's flowbench tests, the Brodix heads flowed 277 cfm (.600-inch lift) on the intake and 222 cfm (.650-inch lift) on the exhaust.
The M2 castings flow over...
The M2 castings flow over 270 cfm on the intake with a 185cc runner volume, but Brodix told us that they have seen 187cc hand-ported units flowing over 300 cfm. Supreme airflow numbers like those are just what one needs when cramming 10 psi of boost into the engine.
Brodix delivers the assembled heads using top of the line hardware from Comp Cams. One-piece stainless valves and titanium retainers are standard equipment and improve the overall durability of the units. Installation was fairly straightforward, and all of the accessory bolt holes have been drilled so you can have all of the comforts that your street car provides, while having plenty of horsepower-making airflow. There's even a provision for the stock air tube at the back of the heads for the smog-conscious individual.
The ST 5.0R heads utilize stock length 6.250-inch pushrods and 7/16 roller rockers must be employed. Since our heads were set up with guideplates, we used the recommended hardened pushrods from Comp Cams. Holdener had also changed the rocker arm studs to 3/8-inch pieces, which we switched back to 7/16 in order to use the Comp Cams 1332-16 Pro Magnum roller rockers that we had.
We received the heads with...
We received the heads with 3/8-inch rocker studs, but we had a new set of 7/16-inch rocker arms therefore dictating the use of these 7/16 studs.
Tech Editor Evan J. Smith...
Tech Editor Evan J. Smith and Associate Tech Editor John Hedenburg VIII began the installation by disconnecting the various sensors and hoses. The engine was relieved of its distributor and the intake manifold was taken off. The author followed with the removal of the P1-SC ProCharger and its mounting brackets.
Next were the valve covers,...
Next were the valve covers, rocker arms and pushrods. Here you can see the accessories have also been removed and the headers have been unbolted.