The Porsche 911.84 is a 3,299 cc, air‑cooled flat‑six petrol engine produced between 1978 and 1983. It featured a single overhead camshaft per bank (SOHC), Bosch K — Jetronic continuous mechanical fuel injection, and a compression ratio of 9.3:1. Rated output was 162 kW (220 PS) at 5,900 rpm with 280 Nm of torque at 4,800 rpm, engineered for performance under evolving emissions standards.
Fitted exclusively to the Porsche 911 SC (G — Series) for global markets, the 911.84 re…
Production years 1978–1983 meet Euro 1-equivalent and US EPA 1978 standards; engine is exempt from modern emissions regulations (KBA Historical Vehicle Registry, Ref. HVR/911/1978).
The Porsche 911.84 is a 3,299 cc air‑cooled flat‑six engineered for the 911 SC (G-Series) (1978–1983). It combines Bosch K-Jetronic mechanical fuel injection with a high-displacement SOHC layout to deliver strong mid-range torque and refined high-rpm performance. Designed to comply with late-1970s emissions mandates, it balances performance with durability through reinforced bottom-end components and revised cooling.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,299 cc | |
Fuel type | Petrol (95–98 RON) | |
Configuration | Flat‑6 (boxer), SOHC, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 95.0 mm × 78.0 mm | |
Power output | 162 kW (220 PS) @ 5,900 rpm | |
Torque | 280 Nm @ 4,800 rpm | |
Fuel system | Bosch K-Jetronic continuous mechanical fuel injection | |
Emissions standard | Euro 1 equivalent / US EPA 1978 | |
Compression ratio | 9.3:1 | |
Cooling system | Air‑cooled (fan‑driven) | |
Turbocharger | None | |
Timing system | Gear‑driven camshafts | |
Oil type | SAE 20W‑50 mineral oil (API SF/CC) | |
Dry weight | 145 kg |
The Porsche 911.84 was used exclusively in the Porsche 911 SC (G-Series) (1978–1983) with rear-engine, rear-wheel-drive mounting and no licensing partnerships. This engine featured platform-specific intake manifolds, reinforced crankshafts, and emissions-specific exhaust systems—and from 1980 catalytic converter-equipped variants replaced thermal reactors in US and select European markets. All adaptations are documented in OEM technical bulletins.
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The 911.84's primary reliability risk is thermal reactor degradation on 1978–1979 models, with elevated incidence in high-mileage or track-used examples. Porsche internal service reports from 1980 noted cracked reactors in over 30% of early 911 SC units after 80,000 km, while KBA preservation audits identify exhaust flow restriction as a frequent cause of overheating in vintage examples. Sustained high-load operation accelerates thermal fatigue in cast-iron reactors, making inspection critical for performance and cooling integrity.
Analysis derived from Porsche technical bulletins (1978–1983) and KBA historical vehicle audits (2010–2023). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
Yes, with proper maintenance. The 911.84 is one of the most robust air-cooled Porsche engines, featuring a reinforced crankshaft and improved cooling over earlier 2.7L units. Valve adjustments every 10,000 km and oil changes every 5,000 km ensure longevity. Many original engines exceed 200,000 km with routine care.
Thermal reactor cracking (1978–1979), K-Jetronic regulator drift, oil leaks from gaskets, and tappet rattle are most frequent. These are well-documented in Porsche TSBs from the late 1970s and remain common in 911 SC restorations.
Exclusively the Porsche 911 SC (G-Series) from 1978 to 1983, in coupe, Targa, and Cabriolet body styles. It was never used in turbocharged or earlier 911 models.
Aftermarket ECU tuning is common on the 911-84 platform, but increasing boost or altering engine parameters accelerates component wear, impacts emissions compliance, and may void vehicle warranties. Any modifications should be evaluated carefully by a qualified specialist.
Approximately 12–13 L/100km (22–24 mpg UK) in mixed driving. Highway cruising can achieve 10 L/100km (28 mpg UK). The K-Jetronic system is less efficient than modern injection but more consistent than carburetors.
No. The 911.84 is a non-interference engine—the piston design ensures valves and pistons never contact, even if timing is lost. This enhances safety during cam or gear failure, though valve damage can still occur from over-revving.
SAE 20W‑50 mineral oil meeting API SF/CC (non-detergent). Porsche recommends against modern synthetics due to seal compatibility. Change every 5,000 km or annually to protect bearings and cam lobes.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
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