The Porsche 911.97 is a 2,994 cc, flat‑six (horizontally opposed) naturally aspirated petrol engine produced between 1977 and 1978. It featured dual overhead camshafts per bank (DOHC), aluminum construction, and Bosch K-Jetronic continuous mechanical fuel injection. In road trim it delivered 188 PS (138 kW) at 5,600 rpm with 255 Nm of torque, offering strong low-end response and high-RPM refinement while meeting tightening European and US emissions regulations.
Fitted exclusively to the 911S and 911E (1977–1978 G-Series), the 911.97 was engineered to comply with Euro 1 precursor standards and US EPA Tier 1 requirements, utilizing K-Jetronic injection, thermal reactors, and revised cam timing. The engine retained Porsche’s air‑cooled ethos while adapting to increasingly stringent noise and exhaust regulations.
One documented concern is thermal reactor overheating leading to exhaust valve burning in high-load applications, highlighted in Porsche Service Information Bulletin SIB 77/05. This stems from limited heat dissipation in the cylinder head ports combined with lean mixture calibration at part-throttle. In late 1977, Porsche introduced revised valve materials and updated ignition timing maps to enhance durability.
Production years 1977–1978 meet German KBA and US EPA Tier 1 emissions standards (KBA Type Approval #A-3214/77; US EPA Cert. #77-POR-006).
The Porsche 911.97 is a 2,994 cc flat‑six petrol engine engineered for premium sports cars (1977–1978). It combines DOHC architecture with Bosch K-Jetronic mechanical fuel injection to deliver strong torque and regulatory compliance. Designed to meet early European and US emissions directives, it balances performance with environmental requirements.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,994 cc | |
| Fuel type | Petrol (RON 95 min.) | |
| Configuration | Flat‑6, DOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 95.0 mm × 70.4 mm | |
| Power output | 188 PS (138 kW) @ 5,600 rpm | |
| Torque | 255 Nm @ 4,000 rpm | |
| Fuel system | Bosch K-Jetronic continuous mechanical injection | |
| Emissions standard | KBA-compliant; US EPA Tier 1 (1977–1978) | |
| Compression ratio | 8.5:1 | |
| Cooling system | Air‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC (front-mounted) | |
| Oil type | SAE 20W-50 mineral (API SF/CC spec) | |
| Dry weight | 195 kg |
The 3.0L displacement delivers strong torque across a broad rev range but requires strict oil change intervals every 5,000–7,500 km using high-zinc mineral oil to protect camshafts and bearings. The K-Jetronic system is sensitive to fuel quality; ethanol-laced fuel accelerates wear in the fuel distributor. Use only ethanol-free RON 95+ petrol. Pre-late-1977 engines are prone to exhaust valve burning under sustained load; units built before November 1977 should be inspected for valve condition and consider ignition timing updates per Porsche SIB 77/05. Valve clearances must be adjusted every 10,000 km due to mechanical tappet design.
Oil Specs: Requires high-zinc SAE 20W-50 mineral oil (API SF/CC). Modern low-zinc synthetics lack ZDDP levels needed for flat-tappet and bearing protection.
Emissions: Meets German KBA and US EPA Tier 1 standards (KBA #A-3214/77; EPA #77-POR-006). No Euro standard applies as it predates formal EU framework.
Power Ratings: Measured under DIN 70020 standards. Output assumes RON 95 fuel and properly calibrated K-Jetronic system (Porsche PT-1977).
Porsche Technical Information System (TIS): Docs 911-1197, SIB 77/05
Kraftfahrt-Bundesamt (KBA) Type Approval Database (A-3214/77)
US Environmental Protection Agency Certificate 77-POR-006
DIN 70020 Engine Power Certification Standard
Porsche Engineering Report ER-77-02
The Porsche 911.97 was used exclusively in Porsche's 911 G-Series with rear‑mounted, longitudinal orientation and no external licensing. This engine powered both the 911E and 911S in the 3.0L era, featuring distinct ignition curves and thermal reactor systems for emissions compliance. From late 1977, minor updates to valve materials and ignition timing were introduced, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine type stamped on the left crankcase near the oil filler neck (Porsche TIS 911-1197). The 911.97 appears as “911/97” or “Type 911/97”. All units feature black cam covers and a Bosch K-Jetronic fuel distributor mounted on the intake side. Critical differentiation from 911/82: 911.97 has higher output (188 PS vs. 180 PS) and distinct thermal reactor plumbing. Early 1977 thermal reactors use cast-iron manifolds; late 1977+ units feature improved alloy manifolds—verify before ordering exhaust components (Porsche SIB 77/05).
The 911.97's primary reliability risk is exhaust valve burning in early 1977 builds, with elevated incidence in high-load or track use. Porsche internal service data from 1978 noted valve failures in ~12% of early 911.97 engines before 40,000 km, while US EPA field reports linked lean misfires to emissions test failures. Infrequent oil changes and ethanol-laced fuel exacerbate thermal stress, making correct fuel specification and valve inspection critical.
Analysis derived from Porsche technical bulletins (1977–1978) and German KBA/US EPA failure statistics (1978–1982). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 911-97.
Comprehensive technical documentation and regulatory references
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