Seat Pressure vs Open Pressure Explained

March 17th, 2026
Seat Pressure vs Open Pressure Explained (Valve Spring Guide)Understanding the difference between seat pressure and open pressure is critical when selecting valve springs for any performance engine. These two measurements determine how well your valvetrain controls the valve throughout its entire motion.If you need recommended pressure ranges, see our Valve Spring Pressure Chart & Guide or use our Valve Spring Calculator to estimate your exact setup.What Is Seat Pressure?Seat pressure is the...

How to Measure Valve Spring Installed Height

March 17th, 2026
How to Measure Valve Spring Installed Height (Step-by-Step Guide)Measuring valve spring installed height is one of the most important steps when setting up a valvetrain. Even a small change in installed height can significantly affect seat pressure, open pressure, and overall valve control.If you're unsure what pressure your setup should have, check out our Valve Spring Pressure Chart & Guide or use our Valve Spring Calculator to estimate your numbers.What Is Valve Spring Installed...

Octane vs Compression Ratio

March 5th, 2026
What Octane Do I Need? Compression Ratio vs Fuel (87/91/93/E85/Race Gas)One of the most common questions we hear is: “What compression ratio can I run on pump gas?” The real answer depends on more than a single number. Fuel octane matters — but so do cam timing, combustion chamber design, quench, air/fuel ratio, ignition timing, engine temperature, and how the vehicle is used.Start here to calculate your engine’s static compression ratio: Fastime Compression Ratio Calcula...

How to Calculate Engine Compression Ratio (Step-by-Step)

March 5th, 2026
How to Calculate Engine Compression Ratio (Step-by-Step Guide)Compression ratio is one of the most important numbers when planning an engine build. It directly affects power, efficiency, fuel requirements, and detonation resistance. Whether you're building a street engine, bracket motor, or high-RPM race combination, knowing your compression ratio helps ensure all the parts in the combo work together.If you'd like to calculate it quickly, you can use the Fastime Compression Ratio Calcu...

Rod Ratio Explained (What it does and doesn’t mean)

March 5th, 2026
Rod Ratio Explained: What It Means for Piston Motion, Side Loading, and RPMRod ratio (rod length ÷ stroke) is a useful reference when comparing engine combinations. It can influence piston motion characteristics, dwell time near TDC, and cylinder wall side loading — but it’s not a magic “best number.” The right choice depends on the entire combination and how you plan to use the engine.On this page:What Is Rod Ratio?Why Rod Ratio MattersWhat Rod Ratio Does NOT DoSt...