H-O Racing's "Rocket Box"

The layout

The "Rocket Box" had to provide a smooth, efficient transition between the throttle bore outlets on the bottom of the 455 Super Duty 800CFM Quadrajet carburetor and the inlet to the manifold mounting plane and plenum. The former cannot be modified in any way per NHRA Super Stock rules, but the latter can be modified in almost any way desired.

As described previously, a rocket exhaust nozzle style transition inside an aluminum spacer block seemed the right idea. The starting point (no spacer) pictured below is the OEM configuration of the Edelbrock Torker-1 mount flange and plenum with the circular outlets of the QJet carb throttle bores superimposed.



A 3in tall block was the tallest that would fit and still have the Trans Am hood scoop fit and even this required modifying the air cleaner. For an 80% bell nozzle with the QJet throttle bore diameters (2x1.219" and 2x2.250" for the SD-455 800CFM QJet) as the venturii diameters (nozzle entrances), the nozzle exit diameters superimposed on the above graphic results in this layout:



A cross section view of the QJet and nozzle outline above looks like this:



Obviously, this will not physically work because much of the nozzle exits are significantly outside the mount flange real estate. However, in real rockets the outlet nozzle can be gimballed in any direction in order to control the flight path of the rocket itself. By gimballing the nozzle shape towards the center of the intake plenum (11.5 degree on the secondaries and 9.5 degree on the primaries), the nozzle exits can be moved inside the mount flange real estate WITHOUT shortening the height of the box.



A cross section view of the gimballed nozzles outline above looks like this:



In the actual "Rocket Box", the Edelbrock Torker 1 flange and upper plenum was modified by grinding (no welding) to make the box-to-manifold transition even smoother. Sorry, there are no pictures of the modified manifold nor of the inside of the box because of "security" concerns at the time.

After designing "Rocket Box" on paper with simple drafting equipment, Craig fabricated the "Rocket Box" over a weekend at Kern's shop (when it was closed for business) on a non-computer milling machine. Craig then hand ground the internal shape to smooth the mill bit marks. The intake plenum was then hand ground to match the "Rocket Box" outlet shapes.

Until this was disclosed by Craig and Kern at the 2011 Pontiac Heaven guest speaker event, no one but Craig, Kern and Ken Crocie knew what the inside looked like.