The Porsche 911.9 is a 2,687 cc, flat‑six (horizontally opposed) naturally aspirated petrol engine produced between 1974 and 1975. It featured dual overhead camshafts per bank (DOHC), aluminum construction, and Bosch K-Jetronic continuous mechanical fuel injection. In road trim it delivered 150 PS (110 kW) at 5,200 rpm with 228 Nm of torque, prioritizing emissions compliance and driveability over peak output due to tightening global regulations.
Fitted primarily to the 911T and 911E (1974–1975 G-Series), the 911.9 was engineered to meet emerging US and European emissions standards, utilizing K-Jetronic injection, revised cam timing, and an updated exhaust with secondary air injection. Compression was reduced to 8.0:1 to accommodate lower-octane fuels required in certain export markets, notably the United States.
One documented concern is K-Jetronic control plunger sticking under thermal cycling, highlighted in Porsche Service Information Bulletin SIB 74/12. This stems from thermal expansion mismatch in the fuel distributor housing and contamination from ethanol-laced fuel, leading to lean misfires and hard hot restarts. In late 1974, Porsche introduced improved plunger tolerances and updated warm-up regulators.
Production years 1974–1975 meet German KBA and US EPA Tier 1 emissions standards (KBA Type Approval #A-3052/74; US EPA Cert. #74-POR-008).
The Porsche 911.9 is a 2,687 cc flat‑six petrol engine engineered for emissions-compliant sports cars (1974–1975). It combines DOHC architecture with Bosch K-Jetronic mechanical fuel injection to balance drivability with regulatory requirements. Designed to meet early US and European emissions directives, it sacrifices peak power for broader fuel compatibility and reduced emissions.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,687 cc | |
| Fuel type | Petrol (RON 91 min. for US models; RON 95 elsewhere) | |
| Configuration | Flat‑6, DOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 94.0 mm × 70.4 mm | |
| Power output | 150 PS (110 kW) @ 5,200 rpm | |
| Torque | 228 Nm @ 3,600 rpm | |
| Fuel system | Bosch K-Jetronic continuous mechanical injection | |
| Emissions standard | KBA-compliant; US EPA Tier 1 (1974–1975) | |
| Compression ratio | 8.0:1 | |
| 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 | 190 kg |
The 2.7L displacement with reduced compression provides smooth low-end torque but requires strict adherence to oil change intervals every 5,000–7,500 km using high-zinc mineral oil to protect camshafts and bearings. The K-Jetronic system is highly sensitive to fuel quality; ethanol-laced or low-octane fuel accelerates wear in the fuel distributor and causes lean running. Use only ethanol-free RON 95+ (or RON 91 minimum for US-spec cars). Pre-late-1974 fuel distributors are prone to plunger sticking; units built before October 1974 should be upgraded per Porsche SIB 74/12. 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-3052/74; EPA #74-POR-008). No Euro standard applies as it predates EU framework.
Power Ratings: Measured under DIN 70020 standards. Output assumes correct octane fuel and properly calibrated K-Jetronic system (Porsche PT-1974).
Porsche Technical Information System (TIS): Docs 911-1109, SIB 74/12
Kraftfahrt-Bundesamt (KBA) Type Approval Database (A-3052/74)
US Environmental Protection Agency Certificate 74-POR-008
DIN 70020 Engine Power Certification Standard
Porsche Engineering Report ER-74-02
The Porsche 911.9 was used in Porsche's 911 G-Series with rear‑mounted, longitudinal orientation and no external licensing. This engine powered the base 911T and mid-grade 911E during the transitional 1974–1975 model years, featuring reduced compression for emissions compliance. From late 1974, minor updates to the K-Jetronic warm-up regulator and fuel distributor 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 911-1109). The 911.9 appears as “911/09” or “Type 911/09”. All units feature black cam covers and a Bosch K-Jetronic fuel distributor mounted on the intake side. Critical differentiation from 911/57: 911.9 has lower compression (8.0:1 vs. 8.5:1) and reduced power output. Early 1974 distributors have silver housings; late 1974+ units use black housings with revised plunger tolerances—verify before ordering replacements (Porsche SIB 74/12).
The 911.9's primary reliability risk is K-Jetronic fuel system instability in early 1974 builds, with elevated incidence in vehicles using ethanol-blended fuel or exposed to frequent thermal cycling. Porsche internal service data from 1975 noted drivability complaints in ~16% of early 911.9 engines within 25,000 km, while US EPA field reports linked lean misfires to emissions test failures. Infrequent oil changes and poor fuel quality exacerbate wear, making correct oil specification and fuel system maintenance critical.
Analysis derived from Porsche technical bulletins (1974–1975) and German KBA/US EPA failure statistics (1975–1979). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 911-9.
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