Porsche 911 Turbo (Type 930) Buyer's Guide

The combination of a robust six-cylinder flat engine and pioneering turbocharging gave the 930 a power delivery that was as fascinating as it was demanding.

The 3.0-litre turbo engine (the original Turbo):

• Compression reduced to 6.5:1 to avoid knocking
• A single KKK turbocharger (type 3LDZ) delivers 260 PS at 5,500 rpm
• Fuel metering by Bosch K-Jetronic

The 3.3-litre turbo engine (the evolution from 1978):

• The charge air cooler arrives, for 300 PS and 412 Nm
• The factory power enhancement (WLS) to as much as 330 PS was possible

Typical weak points on the engine:

• Oil leaks: check the cam covers, crankshaft seals, oil lines and timing case seals
• Head studs: broken or pulled cylinder head fixings mean a complete engine strip-down
• Turbocharger: watch for blue smoke (oil burning in the turbocharger), a whistling noise or a loss of power
• K-Jetronic: faults in the fuel distributor, the warm-up regulator or the injectors cause rough running or starting problems
• Heat exchangers and exhaust: prone to corrosion. Rust-through can let exhaust gas into the cabin
• Valve clearances: neglect leads to a loss of power and to valve damage
• Wastegate: a tired spring gives the wrong boost pressure

Gearbox and clutch:

• Four-speed manual: very robust, but the synchromesh rings wear at high mileages
• G50/50 five-speed (1989 only): coveted for its better ratios and usability
• Clutch: Heavily loaded by the high torque. Setting the omega spring calls for expertise

The wide track and the specific set-up deliver high stability through corners, but they make the Turbo demanding at the limit. The abrupt arrival of boost after the turbo lag can cause sudden oversteer.

Suspension check:

• Dampers: worn Bilstein dampers make the car feel vague
• Bushes and mounts: the rubber parts age and cause knocking noises and imprecise handling
• Wheel bearings: listen for a grinding noise through corners
• Modifications: lowering or coilover kits should be properly documented

Steering: Rack-and-pinion steering without power assistance. Check the track rod ends, the inner joints and the steering damper for play and for any restlessness.

Brakes (a motorsport inheritance):

• Derived from the 917: ventilated discs all round for enormous stopping power
• Callipers: the ATE or Brembo callipers can seize when a car stands. An overhaul is costly
• Fluid: change it every two years to avoid corrosion in the system

A faithfully original car with matching numbers is the decisive factor in holding value and in investment potential.

The DNA check:

• VIN check: compare the number on the body (luggage compartment, A-pillar) with the paperwork. Rule out tampering
• Matching numbers: The engine number (on the case) and the gearbox number must match the delivery records
• Paint and specification: check the colour code (service book, luggage compartment). Verify options (air conditioning, sunroof) against the option codes
• Certificate of authenticity / Kardex: a certificate of authenticity from Porsche, or a Kardex extract, is indispensable in confirming how the car left the factory

Recognising conversions:

• Body: slant-nose conversions carried out later reduce the value considerably compared with the factory original (M505/M506)
• Tuning: power upgrades (a different turbocharger, a different charge air cooler) should be reversible and documented
• History: An original stamped service book and invoices from Porsche specialists are worth their weight in gold

Body and exterior:

• Check the panel gaps (a clean accident record?)
• Measure the paint thickness (body filler?)
• Corrosion check: headlight bowls, the ends of the sills, window frames, the battery box, the area around the fuel filler
• Targa and cabriolet seals: cracks, brittleness, whether they still seal

Interior and electrics:

• Wear on the seat bolsters and cracks in the dashboard
• That every instrument works (the boost gauge in particular)
• Electrical conveniences: windows, sunroof, air conditioning, the hood mechanism
• The smell test: damp or smoke?

Technical check (cold start):

• Leaks in the engine bay (hoses, lines)
• Cold start: any smoke? (blue means oil, black means too rich)
• Noises: knocking, rattling or squealing?
• The arrival of boost: it should be noticeable, but not uncontrollably brutal