The new Kaase Boss Nines with stack injection are available from 429 to 600 cu-in. The Boss Nine is constructed with either a cast-iron or a cast-aluminum engine block and topped with Kaase’s hemi-cylinder heads.

Official Release:

Jon Kaase has announced his latest Boss Nine design, energized by an interesting new intake manifold with a hidden plenum below and stack injection above.

Four-time winner of the Engine Masters Challenge, Kaase has succeeded in investing this new stack-injected Boss Nine engine with exceptional torque and tractability— qualities not usually associated with stack injection. But the hidden plenum on the underside of the Boss Nine intake manifold equalizes the pressures in all induction tracts and provides the engine with a clean, consistent idle, excellent part-throttle performance, and instantaneous throttle response. The plenum also provides for brake vacuum and empowers the MAP sensor, which has a major influence in the metering of the fuel.

Pinned to the wall of a small closet in Jon Kaase’s office a transparent zip-lock bag resides. It contains a tiny piece of carburetor float bowl gasket. Marked on the outside of the bag is the figure $57,500. In the finals of the 2005 Engine Masters Challenge, when Kaase was competing against Lennart Bergqvist for top honors, this tiny piece of gasket had broken off and jammed itself in a main jet, depriving his Pontiac engine of a quarter of its fuel. “It was a very costly misfortune,” commented Kaase, “but on reflection, it could not have happened at a better time, because Lennart succumbed to cancer the following year, and he deserved this victory.” On Kaase’s latest creation, the Boss Nine with stack injection, there are no cork gaskets or main jets, just the most evocative induction system delivering the kind of high performance expected of Kaase. And how was this achieved with stack injection? “A number of things contributed,” he said, “including a hidden plenum located in the bottom of the intake manifold.”

Compared with a carbureted Boss Nine equivalent, the new stack-injection system gives a surprisingly good account of itself. On a typical 520cu in engine with 9.8:1 compression ratio, hydraulic tappets, and running on pump fuel, the stack-injection engine outpaced its carbureted rival by an extra 30 foot-pounds of torque.

Although 520cu in has been the most popular engine displacement, Boss Nines are available from 429 to 600 cu-in. So far the most desirable engines in Kaase’s Boss Nine series have been those producing between 500 and 1,000 horsepower. Constructed with either a cast-iron or a cast-aluminum engine block and topped with Kaase’s efficient hemi-cylinder heads, Boss Nine engines were developed using four intake manifolds. These accept 4150 and 4500-style carburetors, as well as Keith Wilson’s EFI system, and various BDS blower units.

  • Boss Nines available from 429 to 600 cu-in.
  • Constructed with either a cast-iron or a cast-aluminum engine block.
  • Topped with Kaase’s efficient hemi cylinder heads.
  • Boss Nine engines were developed using four intake manifolds.
  • Accept 4150- and 4500-style carburetors, as well as Keith Wilson’s EFI system, and various BDS blower units.