The Aluminum D-ports
Aiming at the mainstream Pontiac street/strip market, Kauffman Racing Equipment (KRE) felt that designing a set of bolt-on aluminum D-port heads would be a worthwhile endeavor, not simply to shave weight, but to take advantage of modern cylinder-head technology. Strides made in port and chamber design since 1955 have been enormous and stand to benefit the Pontiac V-8 in particular, since even the last versions from the late '70s were not that different from the originals. Aftermarket cylinder-head designers often focus on port improvements, but increasing the efficiency of the combustion chambers can transform the engine's performance characteristics entirely, and on the traditional Pontiac, this is an area where factory designs leave a lot to be desired.
The KRE heads use a modern heart-shaped combustion chamber to promote swirl and increase quench. In addition, the spark plug has been moved closer to the center of the chamber to promote a faster burn. These techniques are common to late-model engines. An illustration of what happens when newer chamber technology is applied to older engines can be seen in the Chevrolet Vortec heads, which allow 50-year-old small-block Chevys to make significantly more power with the same displacement, compression, and valve sizes while also gaining octane tolerance-that means more power on cheap gas. Part of the KRE plan was to bring these benefits to the Pontiac V-8.
Standard valve sizes for the KRE D-port heads are 2.11/1.66 inches-this is what our test heads have, and it's the same as Pontiac used on later factory heads. Optional are 2.11/1.77-inch valves, as found on '65-to-mid-'70s factory heads; an additional option of 2.19/1.66 inches is also offered. The KRE heads are also built to accept 1.65:1 rocker arms without modifying the pushrod tubes. Combustion chambers can be ordered in 65 cc (considered race-spec), 74 cc, or 85 cc, the latter two being CNC-machined.
Despite the improvements, KRE states that these heads maintain the same valve centers as a stock Pontiac D-port and are designed to use all the stock parts and hardware with the exception of the head bolts, which are produced by ARP. And even though it wasn't really a design goal, the aluminum D-ports manage to shave nearly half the weight of the iron stockers.
The updated chamber used on the KRE heads (top) should promote swirl and a faster, more complete burn than the factory heads. The big open chamber of the stock heads doesn't offer much quench area, and the spark-plug location contributes to a slower burn, requiring more spark lead. |  |
Nobody was impressed when the KRE heads came out of the box, as the ports look nearly identical to, if not a tad smaller than, the stockers at a glance. But flowbench testing clearly shows that improvements have been made (see the Airflow Data sidebar). Kauffman assures that there is plenty of meat in the castings for port work to bring the numbers up even further. | |