🏷️ Basic Information

Make:

Porsche

Model:

928

Product Type:

Conversion Instructions

Engine Code Original:

M28/15 (early 16V), M28/41 (late 16V), M28/44 (4V, 16V), M28/50 (early 32V), M28/52 (late 32V)

Conversion Target Engine:

32 Valve (4 Valves per Cylinder)

👋 Introduction

Product Category:

Performance Enhancement / Engine Modification

Target Audience:

Porsche 928 owners seeking to significantly increase engine power and performance through a V8 4-valve per cylinder conversion.

Alternatives:

Purchasing a factory 32-valve 928 (GTS), aftermarket performance heads, or other engine swap options.

Performance Gain Potential:

Significant increase in horsepower and torque over 16-valve models due to improved volumetric efficiency.

Technical Focus:

Detailed, step-by-step instructions for a complex engine modification.

📋 Manual Details

Manual Title:

PORSCHE 928 16V to 32V GEAR CONVERSION INSTRUCTIONS

Primary Application:

Modification of Porsche 928 16-valve engines to 32-valve specification.

Estimated Page Count:

Variable (typical conversion guides range from 20-60 pages, depending on detail level and included diagrams).

Manual Type:

Technical Conversion Guide / Modification Manual

Language:

English

Format:

Likely Digital (PDF) or Print-on-Demand. Specific format not explicitly stated but common for specialized guides.

📖 Manual Coverage

Engine Mechanical:

Cylinder head modification, valve train conversion, camshaft installation, piston selection, cylinder block preparation (if applicable for 4-valve heads).

Engine Management:

Fuel injection system adaptation, ignition system considerations for 4 valves per cylinder, ECU remapping or replacement recommendations.

Disassembly Assembly:

Detailed steps for disassembling the 16-valve cylinder heads and assembling the 32-valve components.

Component Installation:

Instructions for installing new camshafts, valves, valve springs, retainers, and potentially piston crowns or connecting rods.

Timing Procedures:

Specific instructions for setting the timing of the new 4-valve cylinder heads and camshafts.

Component Identification:

Identification of necessary 32-valve components (cylinder heads, camshafts, valves, pistons, intake manifold, etc.).

Depth:

Advanced mechanical and engine management modification. Assumes a skilled mechanic with prior Porsche 928 experience.

Diagnostic Focus:

Troubleshooting potential issues arising from the conversion process, such as incorrect timing, fueling, or ignition.

Modification Level:

Detailed instructions for a significant engine hardware modification, bridging the gap between OEM 16V and 32V engines.

📊 Manual Specifications

File Format:

PDF (likely, if digital)

Print Quality:

High resolution diagrams and text (expected for technical guides).

Binding Type:

Not Applicable (if PDF). If printed, likely comb or spiral bound for ease of use in a workshop environment.

Paper Type:

Not Applicable (if PDF). If printed, standard or glossy paper for diagrams.

Manual Completeness:

Specific to the 16V to 32V head conversion. Does not cover general service or overhaul of the entire vehicle.

⚙️ Engine Specifications

Engine Family:

Porsche V8

Displacement Original:

4.5L, 4.7L, 5.0L (depending on 928 model year and engine variant).

Valvetrain Original:

SOHC, 2 valves per cylinder (16 valves total).

Valvetrain Conversion Target:

DOHC, 4 valves per cylinder (32 valves total).

Engine Configuration:

V8

Horsepower Gain Estimated:

Potential for 300-400+ HP depending on the specific conversion kit, supporting modifications, and tuning (factory 16V models ranged from ~240-300 HP).

Torque Gain Estimated:

Significant increase in torque across the rev range.

Original Fuel System:

Bosch L-Jetronic, then Bosch Motronic fuel injection.

Conversion Fuel System Considerations:

May require larger fuel injectors, upgraded fuel pump, and potentially a different fuel pressure regulator to support the increased air intake.

🔧 Transmission

Transmission Options:

Porsche transaxle system (Rear-mounted transmission and differential).

Transmission Types:

4-speed Automatic (AWS - Automatic Transmission) or 5-speed Manual (G-Series).

Gear Ratio Considerations:

The increased power output from the 32-valve engine may warrant consideration of different final drive or gear ratios for optimal performance.

Clutch Requirements:

Upgraded clutch may be necessary to handle the increased torque, especially with a manual transmission.

📐 Dimensions

Wheelbase:

2550 mm (100.4 in)

Length:

4650-4750 mm (183.1-187.0 in), varies by model year.

Width:

1775-1835 mm (69.9-72.2 in), varies by model year.

Height:

1280-1320 mm (50.4-52.0 in), varies by model year.

Curb Weight:

Approximately 1550-1700 kg (3417-3748 lbs), varies by model year and transmission.

🛡️ Safety Features

Historical Safety Features:

Early 928s featured robust chassis design, crumple zones. Later models included airbags and ABS. Specific ratings are less relevant for a modification guide.

Braking System:

Originally 4-wheel disc brakes. Conversion may not directly impact brake system but increased performance requires ensuring brake system is in excellent condition. ABS standard on later models.

Chassis Integrity:

The conversion does not typically alter the chassis structure, preserving its original safety characteristics.

💡 Technology Features

Original Infotainment:

Early models had basic radio/cassette players. Later models featured more integrated sound systems, and optional CD players. Some markets received basic trip computers.

Original Driver Assistance:

ABS (Anti-lock Braking System) became standard on later models. Some models featured early forms of cruise control.

Original Connectivity:

None by modern standards. Focus was on the driving experience.

🔧 Maintenance

General Maintenance:

Regular oil changes, filter replacements, spark plug checks, and belt inspections are critical. Specific intervals for a converted engine may need to be adjusted based on performance use.

Engine Oil:

Refer to original Porsche specifications for the specific 928 model year. Typically a high-quality synthetic oil such as Mobil 1 0W-40 or equivalent, with capacity around 8-10 liters.

Coolant:

Porsche Approved Coolant (G05 or similar phosphate-free antifreeze) with appropriate water mixture (typically 50/50). Capacity around 12-14 liters.

Transmission Fluid:

Automatic: ATF Dexron III or equivalent. Manual: SAE 75W-90 gear oil. Capacities vary by transmission type.

Common 928 Issues:

Cooling system leaks (radiator, hoses, water pump), fuel line degradation, electrical gremlins (especially older wiring), timing belt/tensioner issues on 16V models (though this conversion targets the heads).

Conversion Related Issues:

Potential for improper valve sealing, camshaft timing errors, fueling and ignition mismatches, increased thermal load on components if cooling is not optimized.

📚 Vehicle History

Manufacturer:

Porsche AG

Introduction Year:

1977

Engine Evolution Overview:

Started with 4.5L 16V, evolved through 4.7L and 5.0L 16V variants, culminating in the 5.4L 32V (4 valves per cylinder) GTS model.

32V Development:

The 32-valve configuration was introduced in the 928 GT (1989) and the ultimate 928 GTS (1992-1995), featuring a 5.4L V8 engine.

Production Years:

1977-1995

Production Locations:

Stuttgart, Germany

🏆 Awards & Recognition

Design Awards:

The Porsche 928 was widely praised for its innovative design and engineering, often winning accolades for its GT credentials and unique styling.

Automotive Press Reception:

Consistently lauded for its performance, handling, and luxury GT capabilities, especially in its later 32-valve iterations.

Engineering Acclaim:

Recognized for its advanced engineering, including the transaxle layout and sophisticated V8 engine for its era.