Project Porsche 951 Part 2: Building a Reliable Performance Machine

If you've already tackled the initial teardown and basic restoration of your Porsche 951 (944 Turbo), part 2 is where the real transformation begins. This phase focuses on building a reliable, high-performance machine that can handle everything from weekend canyon carving to track days. In this guide, we'll walk through the key areas that demand attention: engine internals, cooling, fuel system, suspension, brakes, and intercooler upgrades. Every modification is chosen to balance power gains with long-term durability.

Engine Build: Strengthening the Foundation

The 2.5L turbocharged four-cylinder in the 951 is robust, but once you push beyond stock power levels, weak points emerge. The stock rods bend around 350-400 whp, and the ring lands on the pistons can crack. A forged rod and piston set—from brands like JE, Wiseco, or Carrillo—is a must for any serious build. Keep compression around 8.0:1 to 8.5:1 for street friendly boost.

Head Work and Valvetrain

Porting the cylinder head improves airflow, especially on the exhaust side. Upgrade to larger valves (1mm oversize is common) and dual valve springs to prevent float at higher RPM. For camshafts, a mild performance grind (like the 951 specific cam from Elgin) retains good idle while adding top-end power.

Main and Rod Bearings

While you have the engine apart, replace all bearings with OEM or better (Clevite or ACL). The 951's oiling system is adequate, but high-RPM use can stress bearings. A high-volume oil pump from Lindsey Racing or similar is a wise upgrade for track cars.

Cooling System: Keep Your Temps in Check

Heat is the enemy of turbocharged engines. The stock radiator is marginal for a tuned 951, so upgrade to an all-aluminum unit with dual electric fans. A coolant reroute kit (like the one from 944 Boost) improves flow to the rear of the head, reducing hot spots.

Oil Cooling

Add an oil cooler with a thermostat sandwich plate. The 951 already has a small oil cooler, but a larger Setrab or Mocal unit (16-19 rows) with -10 lines is highly recommended. Mount it in the front bumper area for direct airflow.

Intercooler and Charge Pipes

A front-mount intercooler (FMIC) is one of the best upgrades for consistent power. Kits from LR, Vitesse, or EMPI offer bolt-on fitment. Upgrade charge pipes to 2.5 or 3 inch aluminum with silicon couplers to reduce pressure drop and heat soak.

Fuel System: Deliver the Goods

Stock fuel injectors and pump max out around 300 whp. Switch to 72-80 lb/hr injectors (EV1 or EV6 connectors) and a 255 lph in-tank pump. Use a fuel pressure regulator like an Aeromotive unit set to 3 bar. For high horsepower, consider a surge tank and external pump.

Tuning Options

MoTeC or standalone ECUs like MaxxECU, Haltech, or AEM are popular for full control. If you want to keep the factory DME with a piggyback, the VEMS or Lindy adapters work well. A wideband O2 sensor is essential for tuning.

Suspension and Brakes: Stop and Turn

A 951 with increased power needs handling to match. Start with refreshed bushings (polyurethane or spherical for track cars). Coilovers from KW, Bilstein, or MCS offer adjustability. Set ride height per corner for optimal weight distribution.

Sway Bars

Upgrade front and rear sway bars (like those from Weltmeister or Tarret) to reduce body roll. Pair with adjustable end links.

Brake System

Stock 951 brakes are decent but fade on track. Swap to 996/Boxster calipers with 4 pistons front and rear. Use 2-piece rotors and track pads (Pagid, Performance Friction). Brake ducts from the lower spoiler keep the rotors cool.

Drivetrain: Clutch and Transmission

A stock clutch slips above 350 lb-ft. Use a sprung hub clutch from Sachs, or a single-mass flywheel conversion with a performance disc. The Getrag five-speed can handle up to 500 whp with careful driving, but a transmission cooler is beneficial. Change the transmission fluid to Swepco 201 or Redline MT-90.

Body and Interior: Weight Reduction

Strip unnecessary items: rear seats, sound deadening, and heavy power accessories. Install a roll bar or cage for safety. Lightweight seats (Sparco, Recaro) and a fire extinguisher are practical. Keep the AC if you drive in hot climates.

Exhaust System: Let It Breathe

A 3-inch downpipe and exhaust are almost mandatory for any build. Eliminate catalytic converters for off-road use, or use a high-flow cat. The unique sound of the 951 is improved with a vibrant resonator and a straight-through muffler.

Final Recommendation

Start with the engine bottom end and cooling system before adding boost. A forged rotating assembly and upgraded intercooler allow you to run 20-25 psi safely on pump gas. If the budget is tight, prioritize a fresh engine with rod bolts, bearings, and a good tune over cosmetic upgrades. Remember that a reliable 951 is more fun than a garage queen. Use quality parts—cheap knockoffs often fail. Join forums (like Rennlist or 944online) for build threads and specific feedback. With methodical work, your project 951 part 2 can yield a car that outdrives modern machinery and stays reliable for years.