ProMaxx Performance Products

Restore horsepower, compression and fuel economy to that tired engine with one of our factory replacement heads. Matches original performance flow and is available as a complete ready-to-install unit that's fitted with valves and springs...

Promaxx Performance extends its reach into the Jeep market with a Stroker Crankshaft for the inline 6-cylinder 4.0 and 4.2L engines. Internally balanced and machined to factory specifications, this crank is the best bang for your buck to put extra power into your Jeep. Features 3.895 stroke and 2-pi..

Restore horsepower, compression and fuel economy to that tired engine with one of our factory replacement heads. Matches original performance flow. Cast #117 & 403.Valves, valve springs and retainers are not included...

Save time and money with Promaxx Cylinder Head with Valves, engineered as direct replacement for the CJ, Wrangler and Cherokee models. For the 4-Cylinder, 2.5L engine, this cast-iron head is shipped pre-loaded with intake and exhaust valves and hardware, so your installation time is drastically redu..