For the past two issues of CCT, we've shown you how to build a powerful fuel-injected Chevrolet LT4 small-block for your classic truck project. Because the LT1 and LT4 are essentially small-block Chevys, they fit just about anything that can accommodate the Bow Tie V-8. Most LT1 and LT4 builds we've seen have successfully made 350-400 hp and an equivalent amount of torque. Trans Am Racing has taken our LT1 platform a step further with a 383ci stroker kit, an aggressive street roller hydraulic cam-shaft, and LT4 heads with commonsense port work. The result has been numbers better than we ever expected. Let's head out to Westech.
Buttoning It Up
We're going to wrap up our LT4 build with the induction system and a trip out to Westech to light it up. To refresh your memory, our induction system is a Corvette LT4 with a 58mm BBK throttle body. Coupled with the LT4 cylinder heads and a lot of clever port work at Trans Am Racing, we have a lot of potential for great power gains from good old-fashioned hot-rodding tricks.
What Sense In Replacing Sensors?
Whenever you're building a fresh computer-controlled engine, we strongly suggest the use of new sensors and controls in the interest of safe, reliable engine operation. This is the throttle position sensor, which gives the PCM (Programmable Control Module) feedback on throttle position. Elsewhere are sensors that detect coolant temperature, exhaust-gas oxygen content, inlet air temperature, and intake manifold vacuum. All these sensors need to be fresh because they each give the PCM specific feedback on a particular engine dynamic. Without that feedback, performance suffers badly.
We learned on the dyno that we needed a new Idle Air Control (IAC), which controls idle speed by creating a controlled vacuum leak at the throttle body. When we need a faster idle, the IAC creates a larger vacuum leak, which raises rpm. This happens when we turn on air conditioning or put the 4L60E automatic transmission in gear.
 |  Mark specifies Fel-Pro gaskets...  Mark specifies Fel-Pro gaskets on most of his builds. He suggests a thin film of gray RTV around the water passages at the intake manifold for added security. |  To install the 58mm BBK throttle...  To install the 58mm BBK throttle body,... |
 we need parts from the smaller...  we need parts from the smaller factory throttle body.... |  ...Mark removes the hot-water...  ...Mark removes the hot-water manifold from the original throttle body and transfers it to the BBK.... |  We need clean surfaces on...  We need clean surfaces on both the hot-water manifold and throttle body for a leakproof seal. |