Pontiac experimental V8 – 427 Hemi TOHC

This was a project started by Pontiac with the end goal of building a Pontiac 427 Hemi. Pontiac asked Mopar (Chrysler, Dodge, Plymouth) for help in designing it and making it work. Surprisingly, Mopar actually agreed and sent over several of the engineers that designed both the 392 and 426 Hemi. The goal of making a Pontiac Hemi succeeded but was never produced.


  • Thin Wall, Cast Aluminum Block 4.257 Bore x 3.75″ stroke (3.0″ Mains) Forged Steel 6.625″ rods (Ram Air V style) 12:1 compression Mechanical Port Fuel Injection
  • Large Valve Heads: 2.40″ Intake Valve 2.00″ Exhaust Valve
  • Small Valve High Rpm 2.19″ Intake Valve 2.00″ Exhaust Valve
  • Splayed Main Caps, head bolts tie into main caps. Head bolts do not pull on the cylinder wall causing distortion. Cam Drive: Fiberglass Belt Max RPM (High RPM Engine): >8000 rpm Engine Weight: Estimated 550 lb (249 kg) complete
  • Dimensions: Width: 32″ Length: 32″ Height: 24.6″
  • Power: estimated 640 hp (480 kW) @ 7500 rpm