The Porsche 911.42 is a 2,687 cc, air‑cooled flat‑six (boxer) petrol engine produced between 1973 and 1975. It features mechanical fuel injection (MFI), overhead valve (OHV) layout, and dry sump lubrication. In standard form it delivered 118 kW (160 PS) at 5,600 rpm with 228 Nm of torque at 4,200 rpm, engineered for improved emissions compliance while retaining drivability.
Fitted to the Porsche 911 T (G — series) and select European 911 models during the transition to str…
Production years 1973–1975 meet pre‑Euro national emissions standards; no formal Euro classification applies (KBA Germany Type Approval #14721).
The Porsche 911.42 is a 2,687 cc flat‑six air‑cooled petrol engine engineered for the G-series 911 (1973–1975). It combines Bosch mechanical fuel injection with OHV architecture to balance drivability and emerging emissions requirements. Designed before formal Euro regimes, it prioritizes thermal efficiency and mechanical reliability over peak output.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,687 cc | |
Fuel type | Petrol (Leaded, compatible with unleaded with upgrades) | |
Configuration | Flat‑6 (boxer), OHV, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 90.0 mm × 70.4 mm | |
Power output | 118 kW (160 PS) @ 5,600 rpm | |
Torque | 228 Nm @ 4,200 rpm | |
Fuel system | Bosch Mechanical Fuel Injection (MFI) | |
Emissions standard | Pre‑Euro (national type approval only) | |
Compression ratio | 7.5:1 | |
Cooling system | Air‑cooled (fan‑driven) | |
Turbocharger | None | |
Timing system | Gear‑driven camshaft | |
Oil type | SAE 20W-50 mineral oil (API SF/CC) | |
Dry weight | 132 kg |
The Porsche 911.42 was used in Porsche's 911 T (G-series) with rear-engine, longitudinal mounting. Platform-specific adaptations included revised engine mounts and updated cooling shrouds for larger bumper impact absorbers introduced in 1974. From mid‑1974, updated MFI pump bushings and recalibrated mixture settings were implemented, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
The 911.42's primary reliability risk is MFI calibration drift leading to lean running and cylinder overheating. Porsche internal data from 1974 noted elevated valve and piston damage in engines with neglected MFI service, while KBA workshop reports identify oil leaks from aged seals as a secondary concern. The low compression ratio reduces detonation risk but increases susceptibility to carbon fouling under short-trip use.
Analysis derived from Porsche technical bulletins (1973–1976) and Kraftfahrt-Bundesamt (KBA) failure statistics (1974–1978). Repair procedures should follow manufacturer guidelines.
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With proper MFI maintenance and valve seat upgrades for unleaded fuel, the 911.42 is robust. Early engines (pre-mid-1974) may require linkage bushing upgrades. The low compression ratio reduces detonation risk but increases carbon buildup in short-trip use. Regular oil changes and valve adjustments every 10,000 km are essential.
Top issues include MFI calibration drift, valve seat recession (on unleaded fuel), cam/tappet wear, and oil leaks from aged seals. These are documented in Porsche Technical Bulletins PTB-73/05 and service manuals. Electrical and cooling issues are rare due to mechanical simplicity.
Exclusively the Porsche 911 T (G-series) coupé and Targa from 1973 to 1975. These were the base 2.7 L models for markets requiring lower-compression, emissions-conscious engines. All are rear-engine, RWD layouts with 4- or 5-speed manual transmissions.
Yes, but cautiously. Common upgrades include higher-compression pistons (8.5:1+), performance cams, and MFI recalibration. However, the low-compression block was not designed for high boost or aggressive tuning. Period-correct builds stay under 180 PS to preserve air-cooled thermal limits.
Typical consumption is 13–15 L/100km (22–19 mpg UK) in mixed driving due to larger displacement and MFI inefficiencies. Highway cruising yields ~11 L/100km (26 mpg UK). Short-trip driving significantly worsens economy due to thermal inefficiency in air-cooled design.
No. The 911.42 is a non-interference OHV flat-six. If timing fails (unlikely, as it uses gears), valves and pistons do not contact. However, valve train damage can still occur from loose components or excessive clearance.
Porsche specifies SAE 20W-50 mineral oil with API SF/CC rating and ZDDP anti-wear additive (≥1000 ppm). Modern synthetics may cause oil pump cavitation in dry-sump systems. Change every 10,000 km or annually, whichever comes first.
Comprehensive technical documentation and regulatory references
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