The Porsche M 64.21 is a 3,387 cc, air‑cooled flat‑six petrol engine produced between 1999 and 2001. It features a single overhead camshaft (SOHC) per bank, 12 valves, and Bosch Motronic M5.2 sequential fuel injection. In standard form it delivered 221 kW (300 PS) at 6,000 rpm, with peak torque of 361 Nm at 4,600 rpm.
Fitted exclusively to the Porsche 911 (993) GT2 in European and select global markets, the M 64.21 was engineered as a high‑performance, race‑derived variant of the final air‑cooled 911 platform, emphasizing lightweight construction and aggressive power delivery. Emissions compliance was achieved through precise fuel mapping and catalytic converters, enabling Euro 2 compliance in approved markets.
One documented concern is elevated oil temperatures under sustained track loads, highlighted in Porsche Service Bulletin 993 11 1999. This issue stems from the air‑cooled architecture’s limited heat dissipation under extreme conditions, potentially accelerating oil breakdown and bearing wear if not mitigated with auxiliary cooling or oil capacity upgrades.
Production years 1999–2001 meet Euro 2 emissions standards (VCA UK Type Approval #VCA/EMS/9567). Not certified for US or Canadian markets.
The Porsche M 64.21 is a 3,387 cc flat‑six SOHC petrol engine engineered for high‑performance sports applications (1999–2001). It combines air cooling with sequential fuel injection and lightweight internals to deliver race‑inspired power in the final generation of air‑cooled 911s. Designed to meet Euro 2 emissions standards, it balances track capability with regulatory compliance in select global regions.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,387 cc | |
| Fuel type | Petrol (RON 98 min) | |
| Configuration | Flat‑6, SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 100.0 mm × 72.0 mm | |
| Power output | 221 kW (300 PS) @ 6,000 rpm | |
| Torque | 361 Nm @ 4,600 rpm | |
| Fuel system | Bosch Motronic M5.2 sequential injection | |
| Emissions standard | Euro 2 | |
| Compression ratio | 11.3:1 | |
| Cooling system | Air-cooled (oil-cooled heads) | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts | |
| Oil type | Porsche A40 (SAE 15W-50) | |
| Dry weight | 190 kg |
The air-cooled design delivers mechanical simplicity and iconic character but requires vigilant thermal management under high load. Porsche A40 (15W-50) oil is critical due to its high-temperature stability under air-cooling stress. Extended idling or stop-and-go driving should be minimized to prevent oil coking. The engine’s high redline demands strict adherence to warm-up and cooldown protocols, especially during track use. Auxiliary oil coolers and increased oil capacity per Porsche SIB 993 11 1999 are recommended for competition applications to mitigate thermal stress.
Oil Specs: Requires Porsche A40 (15W-50) specification (Porsche SIB 993 12 2000). ACEA A3/B3 equivalent acceptable if A40 unavailable.
Emissions: Euro 2 certification applies to all 1999–2001 models (VCA Type Approval #VCA/EMS/9567). Not sold in North America.
Power Ratings: Measured under DIN 70020 standards. Peak output requires RON 98 fuel and functional catalyst (Porsche TIS Doc. 993-7112).
Porsche Technical Information System (TIS): Docs 993-7101, 993-7112, SIB 993 11 1999
VCA Type Approval Database (VCA/EMS/9567)
SAE International: J1349 Engine Power Certification Standards
The Porsche M 64.21 was used exclusively in Porsche's 993 GT2 platform with rear-engine, longitudinal mounting and no external licensing. This engine received minor running changes—enhanced oil baffling in 2000–2001 models and revised intake runners—and was the final evolution of the air-cooled M64 family before transition to water-cooled architecture. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the rear crankcase near the oil pump flange (Porsche TIS 993-7200). The engine number begins with "64/". The M 64.21 is identified by its 3.4L displacement, absence of turbocharging (unlike the 993 Turbo), and lightweight components (titanium connecting rods, forged pistons). Visual cue: 993 GT2 models feature wide rear body, fixed rear wing, and center-lock wheels. Do not confuse with M64/05 (3.6L) or turbocharged variants—intake manifold and cam cover design differ significantly.
The M 64.21's primary reliability risk is oil thermal breakdown under track conditions, with elevated incidence in competition or frequently spirited use. Porsche internal data from 2000 indicated a significant share of early GT2 engines required bearing inspection before 80,000 km, while owner logs link oil starvation to insufficient cooldown cycles. Extended high-RPM operation without auxiliary cooling accelerates wear, making oil specification and thermal discipline critical.
Analysis derived from Porsche technical bulletins (1999–2001) and historic GT2 owner association logs (2002–2020). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-64-21.
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