Head bolt and main bolt specs vary by engine platform — and the difference matters because you're holding 100,000+ PSI of cylinder pressure with those fasteners. This lookup gives factory specs plus ARP upgrade part numbers for popular platforms.
TTY vs reusable
Torque-to-Yield (TTY) bolts (typical on modern OEM head bolts — LS, Coyote, Hemi, etc.) stretch into the plastic deformation zone for maximum clamping force. They cannot be reused — once stretched, they've yielded and re-torquing won't reach the same clamp load.
Reusable bolts (older engines, all ARP upgrades) stay in the elastic zone. Torque, untorque, re-torque — same clamp load every time. ARP head studs are the standard upgrade for any rebuild where the bolts will see multiple removals or higher-than-stock cylinder pressure.
When to upgrade to ARP
- Boost: Forced induction past stock boost levels. The 700+ HP LS guys are all running ARP head studs.
- Multiple gasket changes expected: TTY bolts are one-time use. ARP studs let you pull heads without buying new bolts.
- High RPM: Higher cylinder pressure peaks need more clamp load to keep gaskets sealed.
- Aluminum block + iron heads: Thermal expansion mismatch loosens stock bolts over time. Studs maintain clamp load better.
Always re-torque after the first heat cycle on any rebuild — stock or ARP.