PORSCHE 964 RESTORATION: THE ENGINE IS BEING COMPLETELY REBUILT

THE 3.6-LITER ENGINE IS COMPLETELY DISASSEMBLED

The starting point is the standard 3.6-liter engine from the Porsche 964.

To ensure that the engine is not only cosmetically refurbished but also technically rebuilt to be reliable, it is completely disassembled. Subsequently, all relevant components are cleaned, measured, and assessed for wear.

This process begins right at the heart of the engine: the crankcase and the crankshaft.

The crankshaft has been fully measured and continues to meet Porsche’s specified dimensional tolerances. Therefore, there is no reason to unnecessarily replace a technically sound component.

CRANKSHAFT AND CONNECTING RODS: INSPECT RATHER THAN REPLACE BLANKETLY

While the crankshaft can still be reused, other components are already showing more significant wear.

The connecting rods are thoroughly reconditioned. The so-called large connecting rod eyes are restored to their exact specified dimensions.

The bushings, in which the piston pins will later run, are also no longer dimensionally accurate and are therefore being replaced.

In addition, the engine will be fitted with, among other things:

• new main bearings
• new timing chains
• new gaskets
• new piston pins

This will gradually restore the crankshaft assembly to a reliable technical condition.

PISTONS AND CYLINDERS AFTER ABOUT 200,000 KILOMETERS

The current engine has covered about 200,000 kilometers.

The pistons and cylinders show signs of normal wear and tear. Their condition is not unusually poor—the components have simply been in service for a long time.

However, since this project involves a comprehensive overhaul, the pistons and cylinders will be replaced.

The piston rings are also already showing play in their grooves. Among other things, this wear can contribute to increased oil consumption.

The new components therefore form the foundation not only for reliability, but also for future performance enhancements.

THE CYLINDER HEADS: THIS IS WHERE MOST OF THE WORK IS DONE

The work on the cylinder heads is particularly extensive.

The sealing surfaces will be reworked to ensure a clean and flat joint once again.

The valve seat rings are also given a new contour. This contour is slightly modified from the original production specification, thereby supporting the planned performance increase.

The valve guides will also be replaced and restored to their original dimensions.

Air-cooled Porsche 911 engines, in particular, show a significant amount of wear in the cylinder heads after high mileage.

LARGER INTAKE VALVES AND SPORT VALVE SPRINGS

The valve train is also undergoing continuous development.

New exhaust valves and larger intake valves are used. The intake valves also have thinner stems, whose dimensions are based on those of the Porsche 993.

Since the engines of the Porsche 964 and Porsche 993 are very similar in design, this solution can be effectively applied to both.

The assembly is complemented by sports valve springs and the corresponding upper and lower spring seats.

This both technically upgrades the valve train and prepares it for future performance enhancements.

TUNING CAMSHAFTS FOR THE NEW ENGINE CHARACTERISTICS

New tuning camshafts are installed in the camshaft housings.

They determine when and for how long the valves open, thereby playing a key role in the engine’s characteristics and power delivery.

The rocker arms aren’t simply reinstalled either.

Their functional surfaces are ground and polished, worn bushings are replaced, and they are then brought back to the specified dimensions.

This restores the engine to like-new technical condition.

HOW THE NEW ENGINE IS BUILT STEP BY STEP

Once the individual parts have been refurbished and prepared, the reassembly begins.

First, the piston and cylinder are assembled.

This is followed by:

• Cylinder Heads
• Valve train
• Camshaft housing
• Intake system
• Engine peripherals
• Exhaust system

Step by step, the disassembled engine is thus reassembled into a complete unit.

THE ENGINE PERIPHERALS ARE ALSO BEING OVERHAULED

The engine overhaul doesn’t stop at the engine block itself.

Numerous attached components are also visually and technically refurbished.

For example, steel parts are freshly galvanized. The entire engine bodywork is repowder-coated.

This results not only in a technically overhauled engine on the inside—the visible components are also refurbished to match the overall condition of the vehicle.

THE DUAL IGNITION DISTRIBUTOR IS OVERHAULED

A distinctive feature of the Porsche 964 and Porsche 993 engines is the dual ignition distributor.

Inside is a small timing belt that can wear out over time.

This will be replaced during the engine overhaul.

The bearings on the distributor shafts will also be replaced, ensuring that the entire unit functions properly again.

A NEW OIL PUMP FOR THE RECONDITIONED ENGINE

The existing oil pump will also be replaced.

A reliable oil supply plays a crucial role, especially in air-cooled engines.

Engine oil not only lubricates numerous moving parts, but also plays a key role in the engine’s temperature management.

That is why the oil pump is also one of the components being addressed in this extensive rebuild.

TYPICAL OIL LEAKS IN THE PORSCHE 964

Another area of focus is the chain cases.

The corresponding sealing surfaces are re-machined and planed to minimize the risk of oil leaks later on.

Porsche 964 and Porsche 993 models, in particular, can be prone to leaks around the chain cases and covers as they age.

Instead of completely replacing technically serviceable components, they are selectively remanufactured.

This allows existing components to be reused effectively while ensuring a proper seal.

WHEN DOES A PORSCHE 964 NEED AN ENGINE OVERHAUL?

There is no set mileage threshold at which every Porsche 964 engine must be overhauled.

Although the approximately 200,000 kilometers on the project engine are a typical mileage at which significant wear can certainly occur, the actual condition of the engine is always the deciding factor.

Typical signs that action is increasingly needed may include:

• Significant oil leak
• Large oil stains under the vehicle
• Increased oil consumption
• Rattling or other mechanical noises
• Declining engine performance
• Increased wear on individual components

The engine itself often indicates when a more thorough inspection is necessary.

WHY A LEAK CAN QUICKLY LEAD TO AN ENGINE OVERHAUL

Oil leaks, in particular, can lead to extensive work on an air-cooled Porsche engine.

Some sealing points are only accessible once the engine has been largely disassembled.

Once this stage is reached, further disassembly often reveals additional wear on components that, after several decades and high mileage, would need to be overhauled anyway.

In such cases, it may make more technical sense to perform a comprehensive engine overhaul right away, rather than simply repairing a single leak.

KEY FACTS FROM PART 3

ENGINE OVERHAUL AND PERFORMANCE ENHANCEMENT: A COHERENT APPROACH

Part 3 shows that the planned performance upgrade for the Porsche 964 isn’t simply achieved through individual tuning components.

First, a technically sound foundation is established.

Worn components are replaced, serviceable parts are precisely reconditioned, and known weak points are addressed.

Only on this foundation are performance-related modifications—such as larger intake valves, sport valve springs, and tuning camshafts—added.

The goal thus remains the same as it has been since the start of the project:

more power, without losing sight of stability and drivability.