Throttle Body

Two steps forward, one step back… again. I have several issues with the induction system. The induction tube was hitting the tail and created a small crack in it. The ID of the weld flange mounted to the supercharger snout created an abrupt transition and it was too close to the supercharger’s o-ring — we don’t wanting that getting sucked in by accident. The LS7 throttle body was large and in the way and there no straight section long enough to mount a mass airflow sensor (I might have a blended MAAF/MAS tune).

I wasn’t sure what to do about it until Allan mentioned pointed out how much smaller the LT5 throttle body was. It’s dimensionally much smaller (see photo below), 32% lighter (2.24 vs. 3.29 lbs.), has a larger diameter (90 mm vs. 95 mm ) and it was designed for a supercharged rather than a naturally aspirated engine. Since I ‘m using a MoTeC ECU there won’t be tuning issues due to a different throttle body.

Of course, I mistakenly ordered a ported LT4 throttle body from Katech which means that I have I now have three throttle bodies. All too often, the third try seems to be the charm! In any event, if anyone needs a LS7 or an LT4 throttle body I’ll cut you a deal.

I spent many hours searching for the correct weld flanges. There are a lot of LT5 adapters out there, but I couldn’t find anything that met my requirements so I designed custom ones. Both have an internal recess to ensure that tube remains concentric with flange ID. The supercharger snout flange smoothly tapers the 4” tube into the snout and the throttle body flange has a groove for an o-ring. One-off CNC parts are spendy and can have long lead times so I 3D printed a couple of prototypes. As can be seen in the photo below, the fit was tight enough to hold it in place so long as you don’t bump it. Abe was able to use them to mock the tubes, but he suggested that I beef up a few areas to prevent warping when welding.

The next step is to find someone to CNC machine them… I’ve been thinking about buying a machine for years, but that might push my wife over the edge. Once I get the the flanges machined and the tube between the supercharger snout and the throttle body tacked in to place, I’ll need to scallop the upper 2” x 2” chassis rail to enable the tube to clear the tail.