A quarter-mile strip of asphalt is not a great distance. But drag racing isn’t about distance. It’s about time. The car that reaches the finish line first wins the race. But the car that wins isn’t always the fastest car or the quickest car. It’s usually the car that runs with the most consistent elapsed time.
Of course, drag racing is all about acceleration too. Launching a vehicle from a standing start and accelerating as fast as possible takes LOTS of horsepower (and traction). Top Fuel dragsters and funny cars are capable of reaching the finish line in about four and a half seconds at speeds in excess of 330 mph. Pro stock cars will cover the same distance in less than seven seconds at speeds over 200 mph. A hot street/strip car may run the quarter mile in 11 to 12 seconds and hit 115 to 120 mph.
Regardless of the class, the rules or the type of fuel these engines burn, one thing all drag motors share in common is cylinder heads that are designed to breathe. Making lots of horsepower requires lots of airflow, especially at high rpm where most of these motors make all their power. Airflow can be increased by boosting the intake system with a supercharger or turbocharger, by increasing the displacement of the engine, by increasing valve lift and duration, and by installing cylinder heads that have been ported and reworked to maximize airflow within a specific rpm range for a given valve lift.
Before aftermarket performance cylinder heads became widely available, the only option drag racers had was to find the biggest stock heads that would fit their engine and have the heads reworked by a professional head porter. The limiting factor with stock heads is the location of the original ports and the thickness of the casting. Airflow can be increased up to a point, but once the physical limits of the casting have been reached further massaging may be impossible.
Aftermarket performance heads open up a whole new world of possibilities because they are cast for a specific purpose. Some of today’s aftermarket “as cast” heads with unmachined ports flow as well as or even better than ported stock heads. Some have raised runners or relocated ports to improve airflow, while others are cast with additional metal to allow extensive CNC (computer numeric controlled ) porting to create almost any port configuration a drag racer wants.
In recent years, the trend in drag racing has been to larger and larger displacement engines. A decade ago, a 500 cid motor was considered huge. Today some drag motors displace over 700 cid. To achieve these kinds of numbers, cylinder heads must be able
to accommodate blocks with 5-inch bore centers. This has created a niche for special heads that can accommodate wider bore spacing.
Choosing The Right Head
For all-out drag racing, cylinder heads that deliver big airflow numbers are usually the best. But for street/strip engines, bigger isn’t necessarily better. In fact, it may be counterproductive for every day driveability.
In theory, the more air a set of heads flows in cubic feet per minute (cfm), the more power they help the engine to make. But in the real world, it’s not so simple. Air velocity is just as important as air volume, especially for street-driven dual purpose vehicles and heavier vehicles with automatic transmissions.
At low rpm, an engine actually breathes better if air velocity in the ports is kept high. Air entering at high speed fills the cylinders more quickly and efficiently. That’s why stock engines have relatively small intake ports, runners and valves. It boosts low rpm air velocity and engine torque. Bolting a set of aftermarket heads with huge intake ports on a relatively stock engine or a small displacement engine that’s going to be driven on the street will probably kill low end torque.
To take advantage of big flow numbers, an engine has to be capable of turning high rpms. It also has to have lots of valve lift and duration, and an induction system that can deliver an adequate volume of air and fuel to the motor. A big set of heads and a killer cam on a 350 Chevy with a stock tuned port induction system is going to run out of air above 5500 rpm.
When looking at the flow numbers for various aftermarket heads, keep in mind that airflow depends on many things: the profile and volume of the runners, the shape of the bowls and combustion chambers, the size of the valves, the angles on the valve seats, the rate at which the valves open, maximum valve lift, duration and overlap.
As a rule, the bigger the engine, the more intake runner volume it needs to flow well at higher rpms. The intake port volume on a stock Chevy 350 small block head is about 160 to 170 cc’s. If you’re installing a 383 stroker crank, the runner size would have to be increased to about 185 to 190 cc’s just to maintain the same airflow as before. If you’re also installing a hotter cam and stiffer valve springs or dual springs so the engine can turn more rpms, the port size might be increased to up to 200 cc’s or more depending on the engine’s rpm range and performance potential.
For big block engines, larger ports are needed. A typical aftermarket street performance head for a big block Chevy might have 265 cc oval ports. A big block racing head, by comparison, might have port sizes ranging from 300 to 420 cc’s or greater depending on the rev limit of the engine.
The best advice for selecting a set of aftermarket performance heads is to follow the recommendations of the head suppliers. They know which port runner volumes and configurations work best for a given displacement and rpm range. This kind of information is readily available in their product catalogs and on their websites.
How much money you spend on a set of heads depends on what you want. A set of bolt-on aftermarket heads for a typical street/strip car might cost $1,600 to $2,000, while a set of high end fully race prepped heads might cost $4,500 or more. If you want titanium valves, beryllium seats and the best springs, figure $6,500 and up for a pair of race heads. A set of custom-made Pro Stock heads might cost upwards of $20,000 a pair. The selling price usually depends on how much labor and machine work goes into the heads.
To find out what kind of new cylinder heads are available for drag racing, we contacted a number of aftermarket suppliers for their input. Contact information, as well as more suppliers of performance heads for circle track and other racing use, is included in a supplier directory.
Air Flow Research
Air Flow Research will be introducing four new Chevy SB cylinder heads this fall: a street head with 180 and 195 cc intake ports, a 210 cc performance head with raised runners for 350 and 383 street/strip engines, a larger 220 cc head also with raised runners, and a 230 cc head with raised runners for serious drag racing. The street heads will be available first, with the rest being out in time for the PRI show in December.
Tony Mamo of Air Flow Research says his company has completely retooled its entire SB Chevy line. “We wanted a cleaner, more modern look with improved port designs and chambers. The four new heads were designed from a clean sheet of paper to incorporate the latest design features and thinking. All of these heads will be CNC ported, even the street heads, and will only cost a couple hundred bucks more than an as-cast head.
Alan Johnson Performance has two new cylinder heads of interest to serious drag racers. One is a solid billet aluminum BB Chevy head with no water jackets. The fully CNC machined head fits standard blocks and intake manifolds, and is available with two intake runner sizes (316 or 368 cc) and two combustion chamber sizes (111 or 118 cc’s). The BB Chevy head with the larger runners flows 407 cfm at .800″ lift.
Also new is a Muscle Head for 426 Hemi dragster engines. This is a CNC machined head that features a flatter valve angle, raised ports and tubeless spark plug holes. The head flows 494 cfm at .800″ lift.
Bob Williams of All Pro says everything his company sells is for small block Chevys. “We think we have the most powerful 23° cylinder head for the SB Chevy, our 245 Series heads. We also have Gen III heads for LS series engines, our new 13° Ultra head in two versions (for stock intake manifolds or special sheet metal manifolds), and a new LS-W 12° full competition style head that is better than any stock LS7 head and can bolt right onto a Z06 Corvette. The LS-W 12° head is much stronger than the stock head and flows 390 cfm.”
Brodix has three new cylinder heads for drag racers. One is the SB-3 24° SB Chevy head with huge 366 cc rectangular ports that flow 425 to 430 cfm. Another is the BB-3 Xtra 24° head for BB Chevy, which is available in several configurations including a CNC ported 366 cc rectangular port, an as-cast 363 cc rectangular port, and a CNC ported 351 cc high velocity oval port that flows over 420 cfm. The third head is the Big Duke PB1803 18° Pro Stock style heads for BB Chevy. These heads have 2.450″ intake and 1.860″ exhaust valves, copper valve seats, and CNC combustion chambers, and as-cast oval ports that flow over 490 cfm. The Big Duke series heads require special pistons, valve covers, head studs, shaft rockers and intake manifold. Heads are available as bare castings or complete.
Jeff Brotherton says Brodix also offers a repair service for restoring its performance cylinder heads to like-new condition. “Sometimes a racer will blow up an engine and chew up a combustion chamber. We can fix that.” Considering the fact that some of these heads can cost up to $4,000 a pair, repairing a damaged head is a lot cheaper than replacing it.
The newest head from Canfield Cylinder Heads is an 18° Ford head for the 5.0L small block. The bolt-on head is a street/strip design with 170 cc runners for good low-end torque. Combustion chambers are 61 cc.
Canfield also has other Ford SB heads including one with 192 cc runners, stock intake runner locations and raised exhaust runners, and a CNC ported version with 212 cc runners for 650 plus horsepower engines. Canfield also has a variety of SB and BB Chevy heads, including 23° SB Chevy heads with 195 and 220 cc runners for 500 to 600 hp motors, and BB Chevy heads with 310 or 350 cc intakes with raised exhaust ports. Fully CNC versions of the BB Chevy heads are also available.
The newest head from Dart Machinery is a 220 series 23° SB Chevy racing head. “Actually, it’s a redesign and reintroduction of a head we used to sell but were not publicizing,” clarifies Jack McInnis. “We redid the ports and chambers and now offer the head bare or complete with stainless steel valves. You can get it with standard runners, raised runners or spread exhaust ports.”
McInnis said Dart introduced a new 18° conventional oval port style head for BB Chevy last year. Another head that was introduced some time ago but is growing in popularity is the Little Chief SB Chevy heads. Originally developed for 400 cid and larger Pro Stock truck engines, the heads make lots of power but require extensive modifications such as relocating the lifter bores, and using a special camshaft and intake manifold. Even so, McInnis says the heads are capable of making up to 1,100 horsepower on a naturally aspirated engine. The CNC machined heads can be bought bare or assembled (jobber price $2,600 each, fully assembled).
Edelbrock is expanding its Pro Port line of performance cylinder heads for professional head porters. These are bare heads with unfinished ports that can be ported to suit. New products include a 24° BB Chevy Pro Port head, and an LS1 Pro Port head (which is also available in a fully CNC machined version with 202 cc intake runners by Lingenfelter Performance Engineering).
The LS1 head features extra thickness so combustion chambers can be machined from for 40 cc to 80 cc volumes without cutting though the casting. The LS1 heads also come with powder metal valve seats and special valve guides.
Also new from Edelbrock is a Performer RPM Ford 351C head with 190 cc high velocity 2V intake port configuration and “Yates inspired” fast burn combustion chambers. The heads fit Ford Boss 302, 351C, 351M and 400M engines.
Edelbrock also plans to unveil a new unfinished Pro Port head for Ford small blocks featuring raised intake and exhaust ports at the upcoming PRI Show in December. The head has no official name yet, but the engineering part number is 77079. Heads will be sold individually and will require a SC1 intake manifold. Also coming by the end of the year will be a new spread port head for 600 cid and larger BB Chevy motors.
Enginequest has bolt-on performance heads for SB Chevy and Chrysler engines. The company’s 23° SB Chevy head is available in four runner sizes (180, 200, 220 & 235 cc’s) with 64 cc combustion chambers. The heads are claimed to deliver 40 horsepower over stock out of the box. For Chrysler 318 and 360 engines, EQ cylinder heads come with 172 intake runner volume with 62 cc chambers.
Cary Chouinard of ET Performance says his company offers up to 26 different versions of its Chevy LS1 head casting for engines ranging from 400 to 2,500 horsepower. ET also has a canted valve version for the LS1 that requires a special intake manifold (which the company also makes). “Basically, we can create almost any head configuration a customer wants, from a stock bolt-on LS1 head to an all-out racing head. A lot of these heads that are ported for a 9-second drag car will also work well on the street with the right camshaft and carburetor.” Chouinard says his company also makes heads for Dodge Viper, the new 5.7L and 6.1L Chrysler Hemi and various Pontiac engines.
Indy Cylinder Heads
Indy Cylinder Heads specializes in performance heads for Chrysler applications, including Hemis, 440s and other engines. Russ Flagle says the company has a new “613” head for a 655 cid drag motor, and another for a 636 Hemi. “These heads are typically run on cars that compete in ‘Quick Series’ classes at local drag strips. The motors make 1200 horsepower on pump gas, 1500 to 1600 horsepower with nitrous oxide, and up to 2100 horsepower with a blower. The heads cost about $5,000 a pair with full CNC porting and titanium valves.”
Flagle says Indy Cylinder Heads is working on some new cylinder heads for the 5.7L and 6.1L Hemi that will provide a 200 bolt-on increase in horsepower over stock heads.
Gunner Bowlin of Patriot Performance, a division of Alabama Cylinder Heads, says the new Patriot Predator LS1 head will be available in October. The head will be available with three runner sizes and feature a thicker deck surface and reinforced rocker supports. The 15° head can be used with stock valvetrain components and will be fully CNC machines. The price will be under $1,900 a pair for fully assembled heads.
“We also have a new CNC machined head for SB Chevy engines. You can buy them with one of three runner sizes (195 to 225 cc’s). When these heads were dyno tested on a 434 cid engine, they produced 45 more horsepower than a competitor’s heads with the same sized ports.
“We also just released a new as-cast Freedom head for SB Chevys. The heads are for street/strip applications, and are available with three runner sizes (185 to 220 cc’s). The heads are available bare or assembled.
“For next year, we are developing a new SB Ford head, and are also working on a new BB Chevy head,” says Bowlin.
Profiler Performance Products has a new LS1 Gen II head for SB Chevy that can handle valve lifts as high as .900″, and features a raised valve cover rail so roller rockers can be used without having to install valve cover spacers. The bare heads with as-cast ports sell for around $1,200 a pair and flow 306 cfm at .600″ lift, which Michael Green says is as good as many CNC ported heads.
“We also have a big block Ford head for engines with 4.600″ bores that flows 520 cfm out of the box. And we are working on a new improved version of our Hit Man spread bore BB Chevy heads for drag racers that will provide even greater flow numbers,” says Green.
David McCarver of RHS Racing Head Service says his company’s new fully CNC ported LS1 head is available with 210 or 225 cc runners. The valve angle has been rolled over four degrees for increased flow, and the thickness of the decks has been increased to .800″ to handle higher compression pressures. The heads also have raised valve cover rails so valve spacers are not needed. The heads are available as bare castings or assembled with a choice of beehive or dual valve springs.
Trick Flow currently offers three types of cylinder heads: a CNC ported LS1 Chevy head with 215 cc intake ports, a 13.5° valve angle for improved airflow, and relocated spark plug holes. Combustion chambers are 64 cc. The company also has a bolt-on 23° SB Chevy head for 327 to 400 cid motors with 175 cc runners and 55 cc combustion chambers. For Ford applications, Trick Flow offers CNC ported R-Series heads with 225 cc intakes that flow 341 cfm at .700″ lift. Combustion chambers are 65 cc. All heads are available bare or assembled.
World Products has a new Warhawk 15° head for Chevy LS1 engines that is available with 200 or 220 cc ports, and 64 cc or 72 cc combustion chambers. The heads have raised valve cover rails so spacers are not needed with aftermarket rocker arms. Heads are available bare or fully assembled with stainless steel valves.
Air Flow Research
All Pro Cylinder Heads
Brzezinski Racing Products
Canfield Cylinder Heads
CNC Cylinder Heads
Diesel Head & Parts.
HRD Racing Heads
Indy Cylinder Head
M2 Race Systems
RHS Racing Head Service