The aFe Silver Bullet throttle body spacer (PN 46-32007) is a billet plate that mounts between the throttle body and intake manifold on the 6.4L Hemi V8. It is machined from 6061-T6 billet aluminum and uses a serrated and helix entry profile that the manufacturer says creates turbulence in the air just before it enters the engine. The manufacturer also says the serrated/helix combination avoids the intake whistle that helix-only spacers produce.
Owners on user forums are divided on performance, and some report no noticeable gain. The case for this spacer therefore rests on the manufacturer's listed figure of up to +12 hp for this application and on its quieter design, not on guaranteed seat-of-the-pants results. It is also the right choice if you run an aFe cold air intake, since the manufacturer lists specific aFe intakes it supports, though some of those require intake tube modification. Searches for a Challenger SRT8 6.4 throttle body spacer, Hemi 6.4 TBS, or serrated helix spacer should lead to this exact part number.
The manufacturer's install sheet calls for #12 x 2-7/8" self-threading screws on 11-and-up V8-6.4L engines. The same sheet specifies #12 x 2" self-threading screws for 11-and-up 5.7L engines and M6 x 70mm machined screws for 05-10 V8-5.7L/6.1L engines, so confirm you are using the furnished set for your engine.
According to the manufacturer, the spacer works with the OE intake and with select aFe POWER intakes: 51-12172, 54-12172, 51-12162, and 54-12162. Those intakes require modifying the intake tube, and the manufacturer states the spacer will not work with other aFe intake systems.
The manufacturer lists up to +12 hp for this application. Owners on user forums are skeptical, and some report no measurable gain from spacers of this type, so treat the number as the manufacturer's claim rather than a guaranteed result.
Per the manufacturer's install sheet, this is a bolt-on job. Disconnect the temperature sensor, remove the OE intake tube, and take out the four throttle body screws while leaving the factory sealing O-ring in place. Set the spacer and gasket between the throttle body and manifold with the "Air-In" side facing the throttle body, fasten with the correct screws and washers, and torque to 5 Nm (48 lb-in). Reinstall the intake tube, tighten all clamps, and retighten all bolts and clamps after 100 miles. Because the torque spec is low, use a torque driver rather than a loose ratchet, and double-check the screw length for your model year before tightening.
