Oldsmobile 400 425 455 MID-AIR™ MidRise Aluminum Intake Manifold [Polished] a rough-running

a rough-running

Speedmaster aluminum adapter spacers allow you to adapt Powerglide to Turbo TH400 automatic transmission tailhousing

Speedmaster Steel main girdles are machined from 1045 steel

oxygen sensors

They will allow for the use of reverse-style transmission valve bodies or switching from a 3-speed to a 4-speed

Oldsmobile 400 425 455 MID-AIR™ MidRise Aluminum Intake Manifold [Polished] a rough-runningThe Speedmaster MidRise Air design features the identical plenum and runner design as the normal MidRise. The main difference is that there is an open area under the plenum chamber. This feature is sometimes called an air gap design. The air flowing under the plenum provides a cooler charge for the incoming air with less heat transfer from the engine. This cooler air charge provides additional power and torque.