Pontiac Cylinder Head Packages - Cylinder Head Symphony
This is a discussion on Pontiac Cylinder Head Packages - Cylinder Head Symphony within the Firebird / WS6 forums, part of the Vehicle Specific category; Pontiac Cylinder Head Packages - Cylinder Head Symphony Part I: Street/Strip Pump Gas Applications While it's true that an engine ...
12-11-2007, 08:20 AM #1
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Pontiac Cylinder Head Packages - Cylinder Head Symphony
Pontiac Cylinder Head Packages - Cylinder Head Symphony
Part I: Street/Strip Pump Gas Applications
While it's true that an engine inhales and exhales through its cylinder heads, simply enlarging the intake and exhaust ports does not always yield airflow improvements. Such action can, in fact, degrade airflow and/or port velocity so much that a casting can be rendered useless in short order. Fortunately for hobbyists, a number of performance-oriented options exist today, and we'll explore several in our two-part story.
We contacted companies that are presently producing or uniquely modifying Pontiac cylinder heads and requested information about the specialized castings each offers. In this issue, we'll discuss the entry-level heads, which may be best suited for street-driven combinations that operate through a wide RPM range in myriad driving conditions, as well as hear some insider information about round-port development within Pontiac.
SD Performance Cast-Iron CNC-Ported
Pontiac's basic cylinder head with D-shaped exhaust ports debuted along with the V-8 in 1955, and the same general intake and exhaust port configurations were utilized on most production engines through the end of V-8 production in 1981. Dave Bisschop of SD Performance in Chilliwack, British Columbia, has greatly simplified the art of porting D-port castings and he has created a new avenue for hobbyists seeking affordable performance while maintaining stock appearance.
"We've written CNC programs for virtually every D-port casting Pontiac produced from 1967 forward, and our basic package starts at $1,195 when using your castings, or $1,395 if we supply the cores," Bisschop says. "We start with bare D-port castings, and after a few hours in our CNC mill, we end up with perfectly ported cylinder heads that flow 250 cfm at 0.550-inch valve lift, at 28-inches of pressure on the intake side, and an exhaust port that flows at least 75 percent of that."
He continues, "We finish them with top quality valvetrain components such as stainless-steel Ferrea valves, Crower springs, Manley retainers, and Comp Cams locks. Spring pressure is set for the type of camshaft that's being used (hydraulic or solid flat-tappet, or hydraulic roller). The castings also receive full bronze valve guides, new pushrod guide plates, and 7/16-inch ARP rocker studs. Simply stated, everything is new, but the actual cylinder head castings."
Port velocity is a critical element in the performance of any street engine, and Bisschop says that he commonly focuses on maximizing throttle response in such applications. "Velocity is very important, especially with a 400," he explains. "The long-stroke 455 is less sensitive to port velocity changes, but throttle response can still suffer. The intake ports of our 250-cfm heads measure around 165 ccs, which keeps velocity high, making them an excellent choice for low-to-moderate rpm 400 and 455ci engines producing between 400 and 475 horsepower on pump gas."
A limited number of extra-cost options are available for the cast-iron heads, and those include hardened valve seats, elongated pushrod holes, and three flange surfacing. "We also offer a 260 cfm program for those wanting slightly more airflow, and that adds $200 to the cost of the 250 cfm package, but once we push horsepower toward 500, we start looking at other options including the various aluminum castings presently on the market," he says.
When asked for his thoughts on the thermal efficiency differences between cast-iron and aluminum, and its effects on performance, Bisschop replied, "There's no doubt that aluminum is less efficient than cast-iron. We've found, with all variables being equal, that an aluminum head needs roughly 3/4 of a point more compression to generate the same power as a cast-iron head. We regularly shoot for a compression ratio of 9.5:1 with iron heads and 10.25:1 with aluminum heads on our pump gas engines."
Kauffman Racing Equipment Aluminum D-Port
Any performance enthusiast with a finger on the pulse of the Pontiac hobby knows the excitement coming from Kauffman Racing Equipment in Glenmont, Ohio. Within the past few years, the company has developed and released a new cast-aluminum D-port cylinder head to achieve maximum performance from specific applications. Jeff Kauffman says the endeavor has been a huge success.
"We developed our heads for the simple fact that we wanted a high-performance, aluminum D-port for street engines," he says. "Many customers already had D-port headers on their cars, so we basically filled a market void. Since port velocity is so important in any street application, we kept intake port volume relatively small, measuring 185 cc, which promotes high velocity. That brings torque in quickly, and we build horsepower off that."
According to Kauffman, the basic casting consists of intake ports that flow approximately 260 cfm at 0.550-inch valve lift, at 28 inches of pressure, exhaust ports that flow 70 to 75 percent of that, and a combustion chamber volume of 65 cc. "The basic bolt-on package starts at $1,750 per pair, and that includes 2.11/1.66-inch diameter, stainless-steel Ferrea valves, Crower valve springs, and new pushrod guideplates and rocker studs."
Another key feature of KRE's castings is the modern fast-burn style combustion chambers. "The chamber shape works very well," says Kauffman. "Dyno testing shows that the heads produce peak power with just 30 to 32 degrees of total spark lead, and any variance outside that range usually causes power to fall off. We can enlarge the combustion chamber volume to 74 or 85 cc using our CNC mill, which increases base price to $1,850 and $1,950, respectively, but doesn't have any effect on spark lead requirements.
"Though we intended for these heads to be high-performance stock replacements, we have customers who use them in street/strip, bracket race, and dedicated race applications. We've developed CNC-porting programs to boost airflow to 290-, 310-, 325-, and 340-cfm for those that might benefit from it. Other extra-cost options include larger 2.19-inch intake or 1.77-inch exhaust valves, and valve springs to accommodate a solid roller camshaft."
When asked which castings sell best, Kauffman replied, "We see a 50/50 split for orders of as-cast intake ports and those with CNC-porting, but chamber volume is a little different. There might be a stretch where 85 cc castings sell best, and then 74 cc castings will sell better. It really depends on the combinations that are hot at the time. Right now, 461 to 467ci stroker engines running on pump gas are very popular, and we're consistently making around 500 horsepower with our as-cast (260 cfm) 85 cc castings and a mild hydraulic flat-tappet camshaft in those types of applications."
Pontiac engineers developed a series of cylinder heads aimed at increasing the high-rpm potential of the division's top performance offerings during the late '60s and early '70s. The castings share one common characteristic-round exhaust outlets. With their well-designed port shapes and excellent airflow characteristics, these castings carried the performance torch when there were few options, and they became the basis for many of today's offerings.
The first Pontiac engine to receive the new "round-port" cylinder head was the R/A-II, which replaced the original R/A 400ci containing traditional D-port castings in May 1968. Like their D-port brethren, the R/A-II cylinder heads (casting No. 96) contained 2.11/1.77-inch intake and exhaust valves, an intake port volume around 153 ccs, with airflow peaking around 210 cfm at 28 inches of pressure. Exhaust flow peaked nearly 20 cfm higher than a D-port, however.
Retired Pontiac engineer, Malcolm "Mac" McKellar, tells HPP that, contrary to popular belief, the round-shaped exhaust outlet wasn't intended to increase airflow, but was instead a convenience for racers. "The D-shaped center exhaust ports made fitting headers difficult, and since serious racers typically replaced the cast-iron exhaust manifolds with tubular headers, we changed the outlet shape to make it easier for them. We revised the exhaust port internally at the same time, however, and that's where the airflow increase came from."
The R/A-IV arrived in 1969, and its round-port cylinder heads featured larger intake ports to improve performance. McKellar says that, when designing the heads, focus wasn't on flow numbers, but more so, a combination of port volume and velocity. "I can't recall us measuring actual airflow often. We simply knew that an engine needed a specific volume of air to run at a certain rpm. Our goal for the R/A-IV was 6,000 rpm, so we increased intake port cross-sectional area to a size we felt would allow the 400ci to accomplish that."
Intake port volume of a '69 R/A-IV cylinder head (No. 722) measures around 180 cc, or nearly 30 cc more than that of a typical D-port casting, and as a result, measured peak airflow increased from roughly 210 cfm to 235. The R/A-IV continued as Pontiac's top offering into 1970, and the cylinder head's intake ports were further revised in a successful attempt at maximizing port efficiency. Numbered 614, port volume of the 1970 casting was similar, but airflow peaked near 240 CFM.
R/A-II and R/A-IV castings were utilized on 400ci engines only, and as such, contained combustion chamber volumes somewhere near 72cc to achieve static compression ratios in excess of 10.0:1. When General Motors mandated that compression not exceed 8.5:1 on any of its divisions' engines in 1971, Pontiac combated the resultant horsepower loss with added displacement, and thus the 455 H.O. was born.
"The 455 could make similar power without revving as high as a 400, so we kept the R/A-IV heads, but with a few changes," says McKellar. The '71 455 H.O. castings (No. 197) were extern-ally identical to No. 614, but the massive combustion chambers pushed the intake port floors upward, which not only reduced port volume to around 170 cc, it also reduced peak airflow to around 230 cfm. The intake ports were mildly revised in an attempt to improve low-lift flow for the 455 H.O. in 1972, and the casting was renumbered 7F6. While intake port volume remained around 170 cc, high-lift airflow further degraded and peaked around 225 CFM.
An engine that many consider Pontiac's greatest effort was introduced at a time when other manufacturers were shifting from performance to emissions. The Super Duty 455 was released for production in midyear 1973 as a complete engine package that boasted maximum reliability and 6,000-rpm capability. It contained a host of exotic components to accomplish that.
The SD-455's cylinder heads (No. 16) were similar to past round-port castings, but the intake and exhaust ports were redesigned to maximize port efficiency. To achieve 6,000 rpm with the larger mill, engineers increased intake port volume to roughly 186 cc, and airflow peaked at or slightly above 240 cfm. These castings are generally regarded as the ultimate performance cylinder head ever produced by Pontiac. Today, a usable pair can draw several thousands of dollars.
Edelbrock is a name most hobbyists correlate with a longstanding history of producing high-performance engine components. Though cylinder heads were among the first products the fledgling company offered decades ago, it wasn't until the mid-'90s that Edelbrock released its first casting for the Pontiac V-8.
"We found a large demand for a high-flow Pontiac cylinder head at the time," says Smitty Smith, Technical Sales Coordinator of Edelbrock Corporation in Torrance, California. "We teamed with Ken Crocie of H-O Racing to develop ours, and patterned it after Pontiac's R/A-IV casting. We specifically retained the round-port configuration because of the wide selection of round-port headers on the market then."
The combined effort produced an aluminum casting with 2.11/1.66-inch valves, an intake port volume of 215 cc, and two distinct combustion chamber volumes-one displacing 72 cc, and the other, 87 cc. According to Edelbrock sales literature, peak airflow in as-cast form exceeds 280 and 270 cfm at 28 inches, respectively-the larger combustion chamber requires that the valve seat be placed higher in relation to the port floor, which subsequently affects airflow.
"We offer a semi-machined version of the 72 cc casting, which allows builders to finish them as needed, and either casting is available fully machined, but bare. Our Nos. 60599 (72 cc) and 60579 (87 cc) are ready to bolt on for around $1,800 per pair," says Smith. "We initially thought of the basic casting as a high-performance replacement for musclecar-type applications, but we've seen it used in every type of Pontiac application imaginable, and that's something we never expected."
When asked if there were any foreseeable changes for the casting in the future, Smith replied, "We haven't had to make any changes yet. It flows well and performs to our expectations, and it continues to sell well too. In fact, our records show continued sales growth even after all this time. So when we consider all that, there doesn't seem to be much of a need to at the present time."
Butler Performance in Leoma, Tennessee, is often associated with hardcore Pontiac performance. Not only has the company produced power-added combinations that generate thousands of horsepower, it has also built some of the quickest, naturally-aspirated Pontiac engines in the country. The Butler family isn't just race oriented, though-they know what it takes to build successful street and street/strip engines. David Butler says his company's mildly-ported Edelbrock heads are a key element to that success.
"They're an affordable option for high-performance, street-driven engines," adds Butler. "Pricing begins at $1,995 for 72 cc castings, and $2,195 for the 87 cc units, and each pair is built to customer order. We start with a bare casting, polish the combustion chambers, and mill the deck surface if it's needed to achieve the desired volume-the aftermarket heads can sometimes vary from the advertised amount. The oil-return holes are modified to promote quicker drain back into the pan, and the pushrod holes are elongated to prevent any issues when using high-ratio rocker arms."
He continues, "We use new stainless-steel 2.11-inch Ferrea intake valves, and enlarge the exhaust to 1.77 inches unless the customer has a small-bore engine like the 350. Our port work increases peak intake flow to 300 cfm at a maximum of 0.700-inch valve lift, at 28 inches of pressure, while still maintaining very good low-lift flow and velocity through 219 cc intake ports. Exhaust flow is typically 70 to 75 percent of the intake flow. Race porting is available at additional cost, and boosts peak flow to 315 to 320 cfm with the standard 2.11-inch intake valve, or 325 to 330 cfm with the optional 2.19-inch unit."
Though Butler Performance uses the highest-quality valvetrain components when assembling the cylinder heads, David adds, "We offer several valvetrain options that include lightweight valves, springs for a solid roller camshaft, titanium retainers, and additional milling to further boost compression. Our heads are fully blueprinted during assembly, and each pair is accompanied by a specification sheet denoting such infor-mation as chamber volume, intake and exhaust airflow, open and closed valvespring pressures, and the point of coil bind."
When asked which offering generates the greatest volume, Butler replied, "We have a large number of customers using the entry-level 87 cc castings on 461 to 474ci engines, and are producing around 500 horsepower on pump gas. They can take their cars to the track and run respectably on weekends, yet the combination is very manageable on the street. That's what seems most popular within the hobby right now."
Any of the cylinder heads featured in Part I of our story could be considered excellent choices for street-driven applications. As McKellar shared, Pontiac learned that a casting with specific port volume may be better suited for a specialized combination producing maximum power within a specific operating range. After hearing what each company says about its offering, it's obvious that a great deal of research and development has gone into ensuring that customers get maximum value from their investment. Stay tuned for Part II, as we explore the next level of offerings presently on the market.
Photo Gallery: Current Pontiac Cylinder Head Packages - High Performance Pontiac Magazine
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