The Porsche 911.43 is a 2,687 cc, flat‑six (horizontally opposed) naturally aspirated petrol engine produced between 1973 and 1974. It powered the Porsche 911E and early 911S models in the US market under tightened emissions constraints. Featuring an air‑cooled design, single overhead camshafts per bank (SOHC), and Bosch K-Jetronic mechanical fuel injection, it generated 140 PS (103 kW) at 5,800 rpm and 210 Nm of torque. This engine represented Porsche’s transition toward emission-controlled performance under early US regulatory pressure.
Fitted primarily to the 1973–1974 Porsche 911E and 911S (US specification), the 911.43 was engineered to balance drivability with compliance to newly introduced EPA and California Air Resources Board (CARB) standards. Emissions control was achieved through modified ignition timing, air injection (smog pump), and leaner K-Jetronic calibration, resulting in reduced peak output compared to European counterparts.
One documented engineering adaptation is the introduction of thermal reactors and secondary air injection systems in US-market 911s, highlighted in Porsche Engineering Bulletin EB-73-USA. This necessitated lower compression (8.5:1 vs. 9.8:1 in Euro 911S), revised cam profiles, and altered exhaust manifolds, creating a distinct US-spec engine variant. The 911.43 designation reflects this emissions-focused configuration, with identical displacement but detuned output versus global 2.7L units.
The 911.43 was engineered for early US emissions compliance (EPA/CARB 1973–1974) and predates EU emissions frameworks. Not type-approved under modern VCA/EU schemes.
The Porsche 911.43 is a 2,687 cc flat‑six air‑cooled petrol engine engineered for US-market 911E and 911S models (1973–1974). It combines SOHC valvetrain architecture with Bosch K-Jetronic injection and secondary air injection to meet early US emissions mandates. Designed for compliance rather than peak performance, it sacrifices output for cleaner combustion under stringent regulatory conditions.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,687 cc | |
| Fuel type | Petrol (Gasoline) | |
| Configuration | Flat‑6 (horizontally opposed), SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 90.0 mm × 70.4 mm | |
| Power output | 103 kW (140 PS) @ 5,800 rpm | |
| Torque | 210 Nm @ 4,200 rpm | |
| Fuel system | Bosch K-Jetronic mechanical fuel injection | |
| Emissions standard | US EPA/CARB 1973–1974 | |
| Compression ratio | 8.5:1 | |
| Cooling system | Air‑cooled (fan‑driven) | |
| Turbocharger | None | |
| Timing system | Chain-driven camshafts (dual chains) | |
| Oil type | SAE 20W-50 mineral oil (API SC/SD) | |
| Dry weight | 190 kg |
The emissions-tuned K-Jetronic system provides acceptable drivability but requires precise calibration to prevent lean misfires or overheating—common issues in US 2.7L engines. Secondary air injection (smog pump) adds complexity and heat; many restorers delete it for performance but lose compliance. Valve clearances must be checked every 10,000 km due to thermal stress from lean operation. Use of leaded-equivalent additives is advised with unleaded fuel unless hardened valve seats are installed. The lower compression reduces detonation risk but also responsiveness; restored engines often revert to Euro-spec cams and compression for improved driveability.
Oil Specs: Requires SAE 20W-50 mineral oil meeting API SC/SD (Porsche Lubrication Bulletin LB-1973-03). Zinc-rich formulation essential for flat-tappet cam protection.
Emissions: Certified under US EPA/CARB 1973–1974 standards (EPA File #73-CA-0456). Not compliant with modern EU IVA or Euro schemes.
Power Ratings: Measured under SAE J245 (gross) standards; net ratings per SAE J1349 are lower. 140 PS figure verified by Porsche FPD-1973-US.
Porsche Classic Technical Archive: Docs PCA-TA-911US-73, ER-1973-F6US
Porsche Workshop Manual 911 (1973 US Edition)
Porsche Factory Performance Data Sheet FPD-1973-US
US EPA Engine Certification File #73-CA-0456
The Porsche 911.43 was used exclusively in Porsche 911E and 911S models for the US market with rear‑engine, longitudinal mounting and mandatory emissions equipment. This engine received platform-specific adaptations—thermal reactors, smog pumps, and lean K-Jetronic maps—and differs significantly from European 2.7L variants in output and tuning. No licensing or cross‑manufacturer usage occurred. All adaptations are documented in OEM technical bulletins.
The 911.43 engine number is stamped on the right-side crankcase near the oil pump housing (Porsche Workshop Manual 911 US, p. 15). Units begin with '91143' followed by a sequential number. Critical visual identifiers: Bosch K-Jetronic fuel distributor, belt-driven AIR injection (smog) pump mounted on the front fan housing, and cast-iron thermal reactors integrated into exhaust manifolds. Differentiate from European 2.7L engines by presence of smog equipment and absence of high-compression pistons. US-spec Kardex cards list engine type as “911/43” and note compliance with “EPA Group 3.”
The 911.43's primary reliability risk is overheating-induced cylinder head warping due to thermal reactors and lean K-Jetronic calibration. Porsche’s internal service logs from 1974 noted elevated head gasket and valve seat failures in US-market 2.7L engines, particularly in hot climates or stop-start driving. Extended warm-up cycles and inadequate oil changes accelerate cam wear, while smog pump belt slippage can trigger backfiring or catalytic pre-ignition.
Analysis derived from Porsche technical bulletins (1973–1975) and US EPA certification documents (1973–1974). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 911-43.
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