Gearhead Pro

From a hobby gearhead to a professional engine or chassis builder, you’ll want Gearhead Pro! Gearhead Pro is the calculator app that us gearheads use for many performance automotive parameters. It calculates or estimates numerous engine, exhaust, gearing, tire, suspension, acceleration, weather effects, and other vehicle parameters along with automotive unit conversions and fastener torque and threading parameters. Gearhead Pro works in both standard and metric units and even has advanced settings to customize the calculations to your specific scenario so you can select the most compatible parts for your application.

Gearhead Pro calculates or estimates:

Speed/Gearing
- Engine RPM from vehicle speed, gearing, tire size
- Vehicle Speed from engine RPM, gearing, tire size
- Axle Gear needed for a specific RPM at a certain speed with a given tire size
- Tire Diameter and Cross section width from sidewall size
- Simple gear ratios based on drive and driven tooth count

Boat
- Boat Speed from propeller pitch, slip, RPM and gearing
- Boat Propeller Slip from pitch, RPM, Speed, and gearing
- Simple gear ratios based on drive and driven tooth count

Engine
- Displacement from cylinders, bore, and stroke
- Bore/Stroke ratio
- Static Compression Ratio
- Average Piston Speed
- Airflow
- Airflow w/boost pressure
- Connecting Rod Ratio
- Maximum connecting rod angle from cylinder axis
- Compression Height (piston wrist pin height)
- Dynamic Compression Ratio from the point the intake valve closes
- Effective Compression Ratio (both static and dynamic) using boost pressure
- Piston Position relative to crank angle from TDC
- Head gasket volume (from bore and compressed thickness if round)
- Valve opening and closing events from the cam duration, IC, and LSA
- Cam specs from the valve opening and closing events
- Valve overlap
- Valve lift based on new rocker ratio or lobe lift and rocker ratio
- Valve spring forces from valve spring specs to actual installed height and lift
- Mark dimension on your balancer to set a desired timing advance

Engine Externals
- Minimum air filter size for your engine
- Recommended header primary tube size for your engine
- Recommended exhaust size for your engine
- Cross-sectional flow area of a pipe, or the pipe size from a desired flow area
- Pressure ratio and mass airflow for turbocharger selection
- Power potential of a turbocharged engine configuration
- Pressure ratio and airflow for supercharger selection
- Power potential of a supercharged engine configuration
- Starting pulley ratios and sizes for a supercharged engine

Suspension
- Instant center, Roll Center and Axis, and Anti-Squat of a 4 link rear suspension
- Cg height of your vehicle using the raise one end method
- Combined and secondary spring rates of a dual spring coil-over setup

Weather
- Specific humidity
- Air Density Index
- MSA density altitude
- Power Correction Factor of the current weather conditions

Power
- Power from Torque and RPM, or vice versa

Fasteners and Threading
- Convert fastener torque units to your torque wrench unit
- Lookup or calculate a cutting tap drill size either standard or custom thread
- Torque of a fastener based on thread size and pitch, fastener grade, thread finish…
- Minimum thread length engagement of a fastener in a tapped hole

Unit Conversions
- Length
- Area
- Volume
- Absolute Pressure
- Engine Vacuum/Boost
- Temperature
- Speed
- Volume Flow
- Mass Flow
- Power
- Torque
- BSFC

Fuel System
- Total Fuel system flow for fuel pump selection
- Fuel injector flow for injector selection
- Convert an injector flow rating to a new pressure or flow

Acceleration
- Power of your engine based on your drag racing performance and weight
- Drag performance based on power and weight
- Time you would run on a ¼ mile track (.4 km) based on 1/8 mile (.2 km) performance
- ET or speed based on a previous ET or speed and a weight or weather change
- More power needed to achieve a new ET or speed

Recent changes:
Added Piston Position calculator
Information pages access more intuitive