Engine-build.com — Free Engine Builder Calculators

Free engine building calculators and reference tools for machinists and DIY engine builders. No accounts, no paywalls.

Calculators

• Compression Ratio Calculator — Static and dynamic compression ratio with octane recommendations. Includes Pat Kelley dynamic CR algorithm with rod length.
• Engine Displacement Calculator — Calculate engine displacement in cubic inches, CCs, and liters from bore, stroke, and cylinder count.
• Piston Ring End Gap Calculator — Application-specific ring gap recommendations for NA street, NA performance, forced induction, and race builds.
• Cam Duration & Timing Calculator — Full Vizard cam analysis: valve events, overlap, LSA recommendations, dynamic compression ratio, and rocker lift table.
• Connecting Rod Ratio Calculator — Calculate rod ratio (L/S) and compare against common engines like SBC 350, LS1, Ford 302, 2JZ.
• Horsepower & Torque Converter — Bidirectional HP to torque conversion with Nm and kg-m unit conversions.
• Piston Speed Calculator — Mean and peak piston speed in feet per minute with color-coded safety zones.

Camshaft Selection Guide

Cam Guide — The systematic approach to selecting the right camshaft for your combo. Includes cam comparison tool, valve spring calculator, and Vizard LSA recommendations.

Engine Specs Database

Browse engine specs — bore, stroke, displacement, compression ratio and rod ratio for engines across 34 manufacturers, organized by manufacturer and family. Every engine links into the calculators with its dimensions already filled in.

Common Engine Reference

Small Block Chevy 350: 4.000" bore, 3.480" stroke, 349.8ci, 5.7L. Stock compression 10.8:1 with 64cc heads. Rod length 5.700", rod ratio 1.638.

GM LS1 5.7L: 3.898" bore, 3.622" stroke, 346ci. Rod length 6.098", rod ratio 1.684.

Ford 302 Windsor: 4.000" bore, 3.000" stroke, 302ci. Rod length 5.090", rod ratio 1.697.