One of the most important pieces to the engine-combination puzzle is the cylinder heads. But navigating through the 30-plus offerings (for the small-block Ford) can be overwhelming. There are cylinder heads suitable for use in stock rebuilds, Outlaw-style engines making upwards of 2,000 hp, and every combination in between. Factor in ported-head options, and it could make one's head spin around like a scene in The Exorcist.
This month, we ventured to JPC Racing, where Burcham had a supercharged 5.0-liter Mustang ready to show the effect of improperly sized cylinder heads. We'll sample the Brodix LH 17-degree cylinder heads, which fit a variety of combinations. The LH heads are available in two different intake port volume sizes (195cc and 210cc)-both styles feature a 17-degree valve angle. The two different sizes allow this head to be useful in a variety of applications.
The '89 coupe features a Ford Racing 331ci short-block based on the Ford Racing Boss 302 block, and it's been punched out with a 4.125-inch bore. The folks from Ford then filled it with an Eagle 3.100-inch-stroke crank, Eagle steel rods, and Mahle forged pistons. The short-block is durable, and boost is provided by a Paxton Novi 2200 supercharger system.
Brodix sells its 17-degree...
Brodix sells its 17-degree heads with CNC-porting from Keith Craft Racing Engines, a well-known engine shop credited with providing the power for the first official Pro 5.0 pass in the 7-second zone back in 1998. It has provided powerplants for countless championship titles in NMRA, FFW, and other racing sanctioning bodies. Brodix has a working relationship with the noted Ford engine shop, and these heads are one of many projects the two companies have collaborated on. These heads feature 210cc intake runners and flow over 300 cfm at high valve lifts.
Initial dyno-testing showed the car was producing 477 rwhp when equipped with a pair of 170cc cylinder heads from another manufacturer and 10 psi of boost. While the baseline heads are great, the runner size was not large enough for a stroker, let alone one capable of withstanding a lot of boost.
No matter what combination you are building in terms of cost and performance, you need to be armed with information, and it has to be more than just cubic-feet-per-minute flow numbers. The flow numbers are only part of the story; port volumes play an important roll in performance, as shown by the new the Brodix LH heads.
"There are so many variables when picking a cylinder head: flow numbers, port size, combustion chamber, quality of the head, intention of your combination, and of course, retail cost and budget," said Justin Burcham of JPC Racing. He summed up the major downfall in the cylinder head department: "Bigger isn't always better. The engine size, combination, and level of competition/use (drag racing, street-use, circle track, autocross, and so on) has a bearing on which cylinder heads are correct for your application."
Our test 331ci engine uses...
Our test 331ci engine uses a FRPP short-block with a Boss block, steel crank and rods, and forged pistons. The engine wore a set of aluminum 170cc heads, which are more suited to a smaller cubic inch engine.
Eric Holiday of JPC Racing...
Eric Holiday of JPC Racing cleans the Boss block's deck surface after the heads are removed. It is important to have a clean deck before installing new head gaskets and heads.
The ARP studs, which we picked...
The ARP studs, which we picked up from Summit Racing, were screwed into the block. The Boss block requires a specific set of studs, so be careful not to reuse a set from a different engine block.
Jason Neugent of Brodix heads offered some insight in selecting a cylinder head based on the port volume. "If it is a small-cubic-inch engine with low compression, I suggest you look for a smaller intake runner. The small intake runner will keep the torque healthy and perform well across the board. If you run a small engine with lots of compression, then more cylinder-head intake volume is required to fill the cylinders. The same goes for larger cubic-inch combinations."
A typical street engine in naturally aspirated trim (mild hydraulic roller camshaft, good intake manifold, and properly sized exhaust system) should generally require a 170-200cc runner for 289-347 ci and 195-225cc for 347-440 ci, according to Neugent. "Of course, there is a gray area, so to speak," he added. Those gray areas include high-rpm applications that require a larger intake port to feed the engine, which usually comes with the sacrifice of low-end torque. Supercharged combos can also benefit from a larger set of heads due to extra airflow being shoved into the engine.
Holiday installed a checker...
Holiday installed a checker spring on the head, inserted a pushrod, and bolted down a rocker arm in order to check piston-to-valve clearance. The heads feature 2.08-inch intake valves, and Burcham and Holiday checked to make sure the larger valves cleared the piston valve reliefs.
"In most cases, the valves...
"In most cases, the valves and springs included are adequate for the intended use, but there are exceptions to the rule. If you have an aggressive camshaft profile, or a larger camshaft than what the valvesprings are rated, a spring/retainer change will be necessary," said Burcham. He says these heads have a heavier spring due to the boost and 6,500- to 7,000-rpm capabilities of the engine.
The Cometic MLS gaskets were...
The Cometic MLS gaskets were prepped with Permatex Copper Spray-A-Gasket. Here is where opinions vary on prepping MLS gaskets-some use a spray for added protection, while others install them dry. The JPC shop sprays the gaskets on all of its customer vehicles and NMRA championship-winning team cars.