Hemco Machine Company, Inc. - Buick Turbo V6 Plenum

We were often curious why head gaskets seldom blow on #1 and #2 cylinders. This led to extensive flow testing of a stock type intake and Plenum covers. The results of these tests led us to believe that since fuel was distributed equally to each port by the injectors and that air flow was so unequal in distribution (per the results of the testing), that the front cylinders were running very rich in comparison to the others. It is common knowledge that leaner cylinders are more prone to detonation than richer cylinders. So Hemco set forth to enhance airflow to all cylinders while trying to increase equalization of air flow to all ports. If this could be accomplished then all cylinders could have the proper air/fuel mixture.

A whole new casting design and concept was developed to achieve this effect. Other existing products on the market include: plates welded on an angle inside a stock Plenum cover, poured epoxy liners in a stock Plenum cover and machined billet Plenum covers, to name a few. All of these concepts generate a sloping angle to the rear of the Plenum cover, which aggravates the condition already existing in the stock Plenum. Air is forced into the rear cylinders while the front cylinders are still starved for air.

The Hemco Plenum cover(s) incorporates a radius curve 90-degree turn, cast into the Plenum cover, with a specially shaped opening into the intake manifold. This design causes the intake manifold to react as if a throttle body was sitting on top of it and increases the total CFM airflow even through a stock throttle body.

A seventh injector was developed to richen, or add fuel to the rear cylinders. With the Hemco system a seventh injector is not required because air distribution to all cylinders is enhanced. Any additional fuel needed, can be achieved by increasing the fuel pressure, injector size or injector PW.

After selling a couple hundred Plenum covers and hearing of the increases in MPH and better ET's, the people at Hemco are so confident of their product that we offer a money back guarantee if you are not satisfied with it's performance. You don't need a 10 second car to take advantage of the Hemco Plenum. The Hemco Plenum enhances the performance of any Buick Turbo Car. Similar gains in performance can be seen with a stock type application or a highly modified car. Hemco recommends adding three to four pounds of fuel pressure when replacing the factory Plenum cover due to the additional airflow of the new Hemco Plenum cover.

The stock type 58mm throttle body's have worked well with the Hemco 62mm Plenum cover. The throttle body can be machined "expanded at the exit" to the 62mm diameter quite easily and adds additional air flow capability still utilizing the stock throttle body. For a highly modified combinations, we recommend ACCEL DFI Spark/Fuel Management Systems for added fuel control. These and similar Engine Management Systems are available through White Racing & Marine at the following hyperlink: White Racing & Marine. They offer years of experience in tuning and installation on Buick Turbo Cars and all other EFI applications.