A dyno number at the tires is only part of the story. To understand what this small-block Chevy is really working with, we instrumented the truck to compare ambient air density at the nose to manifold air density at the engine. That means measuring pressure, temperature, and humidity, then watching how much density is lost through the air cleaner and intake path. We used a Banks iDash with a 4-Channel Analog Module, an AirMouse for ambient conditions, plus intake air temp, manifold pressure, coolant temp, and EGT sensors. That gives us a real baseline before any changes are made. On a naturally aspirated engine, any drop between ambient and manifold density is lost potential. If you want to know where the power went, this is how you find it.
In this episode of Banks Built, the team begins establishing a baseline for a 1966 Chevy C20 before making any modifications. The immediate goal is not just to measure horsepower on the dyno, but to understand the engine more completely by collecting the data needed to calculate manifold air density. That requires adding sensors to an otherwise rough, improvised engine bay and integrating them into Banks instrumentation.
Jay brings in Eric from the mechanical engineering group to help determine what needs to be measured and where the sensors can be installed. The truck has been sitting outside for months, and once the hood is opened, the condition of the engine confirms that this will not be a clean installation. The small-block Chevy is a Mr. Goodwrench 350 with an Edelbrock intake and a visibly mixed assortment of hardware, including improvised cooling-system parts. Even so, the plan is straightforward: instrument the truck, gather baseline data, and then use that information to guide future changes.
The measurement plan starts with the variables required to determine manifold air density. First, the team needs ambient conditions outside the engine, including pressure, temperature, and humidity. For that, they use a Banks AirMouse ambient density system mounted at the front of the truck, where it can sample incoming air.
Inside the engine system, they need intake air temperature in the manifold region, manifold pressure, coolant temperature, and exhaust gas temperature. Eric identifies a practical location for the intake air temperature sensor by welding a bung near the air-cleaner assembly rather than drilling and tapping the manifold for that channel. For manifold pressure, the Edelbrock intake already has a plugged port that can be repurposed for a pressure sensor, avoiding unnecessary machining. Coolant temperature will be measured directly in the block because the truck's factory gauges are not trustworthy. Exhaust gas temperature, or EGT, will be measured by adding a probe to the exhaust side of the engine.
The objective is to capture enough information to compare ambient air density at the nose of the truck with manifold air density at the engine. Because the engine is naturally aspirated, the team expects to see a loss between those two points.
The sensor package is built around Banks iDash instrumentation. The episode highlights the iDash DataMonster, which differs from the SuperGauge by adding data-logging capability. According to the team, the DataMonster can record up to 100 channels at 20 samples per second for a month straight on a microSD card. All of the analog sensor signals are routed through a Banks four-channel analog module, which converts them into data the iDash can display, calculate, and record.
The sensors shown include the AirMouse for ambient conditions, an intake air temperature sensor, a 50 PSI pressure sensor for manifold pressure, a closed-element coolant temperature sensor, and an analog EGT sensor. The analog EGT setup is chosen instead of a dedicated thermocouple module because a full thermocouple module would be excessive for this job. The iDash will be mounted in the cab so the team can watch the values in real time during dyno testing.
A quick demonstration confirms that the AirMouse is actively reporting environmental changes. When warm breath is blown across it, the displayed values respond immediately, including a rise in relative humidity. That verifies the sensor chain is functioning before installation is finalized.
The episode pauses to explain why Banks cares about manifold air density rather than horsepower alone. Air density combines pressure, temperature, and humidity, and the team describes it as the ultimate arbiter of horsepower. The denser the air entering the engine, the more oxygen mass is available, and the more power the engine can potentially make.
Gale explains the concept using local atmospheric conditions near sea level. At Banks' location, ambient air density is about 72 pounds per 1,000 cubic feet. In other words, 1,000 cubic feet of air would weigh 72 pounds on a scale. Measuring cylinder air density directly would be difficult, so manifold air density is used as the next best indicator of what the engine is actually receiving.
By comparing ambient density from the AirMouse with manifold density calculated from the intake-side sensors, the team can quantify how much density is lost between the front of the truck and the intake manifold. That loss represents a reduction in the engine's ability to make power. The episode also notes that the Banks iDash is able to calculate manifold air density because that function is patented.
With the measurement plan established, the team chooses a practical, temporary installation approach rather than a polished one. The four-channel analog module is mounted under the hood using existing holes and zip ties. The AirMouse is zip-tied to the front grille so it can sample ambient air at the nose of the truck. Wiring is routed along existing structures, including the top of the engine bay and the firewall, to reach the various sensors with minimal fabrication.
The intake air temperature sensor is installed by welding a bung onto the air-cleaner area and threading the sensor into it. The manifold pressure sensor is fitted into the plugged port on the Edelbrock intake. For coolant temperature, the team removes a fitting in the block and adapts the Banks sensor into place. Because they do not have the exact adapter combination needed, Eric improvises a stacked arrangement of fittings that Jay jokingly describes as a leaning tower. Despite the appearance, it provides the needed connection point for the coolant sensor.
Throughout the installation, the emphasis is on getting accurate data from a rough truck with minimal wasted effort. The truck is not being restored at this stage; it is being instrumented well enough to establish a meaningful baseline.
Installing the coolant temperature sensor requires opening the cooling system, and that turns into one of the messier parts of the episode. Draining the radiator does not go smoothly, and coolant spills onto the floor before the team gets it under control. After cleanup, the new coolant temperature sensor is installed in the block using adapters.
Once the sensor work is complete, the cooling system is refilled using a vacuum-fill tool. The tool pulls roughly 25 inches of mercury of vacuum on the cooling system, then uses that vacuum to draw fresh coolant back in. This method reduces mess and helps refill the system more cleanly than simply pouring coolant into it. The process is presented as an efficient way to restore the cooling system after sensor installation.
The final missing measurement is exhaust gas temperature, which requires getting the truck on a lift and inspecting the exhaust hardware from below. The team initially considers drilling and tapping the exhaust manifold directly, but the manifold is heavily rusted. Since the truck only needs to survive baseline testing and perhaps a single dyno session in its current form, removing the manifold or risking major breakage is judged to be a poor use of time.
While inspecting the exhaust, Eric points out the heat riser valve. He explains that it is a mechanical warm-up device with an internal valve that stays shut when the engine is cold to help the engine warm up faster. As temperature rises, the spring relaxes and the valve opens so the exhaust can flow normally. It is a period-correct mechanical feature that still functions independently of any electronics.
To place the EGT probe without disturbing the manifold, the team looks for a weldable location as close to the manifold as possible on the driver's side, which also simplifies wiring because the analog module is already mounted on that side. The chosen area is farther downstream than ideal, near a bend in the exhaust, because the manifold itself is too corroded to trust for drilling or blind welding. Considerable grinding is needed just to expose enough clean material for the bung installation.
By the end of the episode, the truck has been fitted with an ambient AirMouse in the grille, an intake air temperature sensor above the air filter, a manifold pressure sensor in the Edelbrock intake, a coolant temperature sensor in the block, and an EGT probe mounted in the exhaust system as close to the manifold as practical. All of those signals are routed into the Banks four-channel analog module and then into the iDash for display and logging.
The result is a data package that will let the team do more than report a horsepower number. They will be able to observe ambient conditions, intake temperature, manifold pressure, coolant temperature, and exhaust gas temperature, then use those values to calculate manifold air density and compare it with the density available at the front of the truck. That comparison should reveal how much the naturally aspirated induction path is costing the engine before any modifications are made.
The episode closes with the truck nearly ready for the dyno, but not without a warning about what comes next. In the following installment, the C20 is finally put on the dyno, where another problem appears: the truck is leaking gasoline heavily. That suggests the baseline test itself may be short-lived, but the instrumentation work completed here ensures that whatever run the truck manages will produce useful engineering data.