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964 · 1991–1992 HaloAir-cooledManual only

1991 Porsche Turbo

3.3 L flat 6 turbo · RWD · Coupe · air-cooled

Power
315hp
Torque
332lb-ft
0–60
4.8s
Weight
3,274lb
lb / hp
10.4
Displacement
3.3L

Specification

US-market 1991
Power 315 hp
247 700
Weight 3,274 lb
2,910 3,640
Weight to power 10.4 lb/hp
4.6 lower is quicker 13.0

Where this car sits against every 911 in the catalog.

Engine
Engine code M30/69
Layout flat 6, air-cooled
Displacement 3.3 L
Aspiration Twin-turbocharged
Power 315 hp @ 5,750 rpm
Torque 332 lb-ft @ 4,500 rpm
Redline 6,650 rpm
Specific output 95 hp / L
Chassis & body
Drivetrain Rear-wheel drive
Body styles Coupe
Transmissions 5-speed Manual
Curb weight 3,274 lb
Wheelbase 89.4 in
Length 168.3 in
Width 69.9 in
Height 51.4 in
Performance & market
0–60 mph 4.8 s
Top speed 168 mph
Weight to power 10.4 lb / hp
MSRP when new $95,000 base

About the 1991 Turbo

1991Turbo arrives using a developed version of the 930’s 3.3 rather than the new 3.6.

TurboThe 964 Turbo launched using a developed version of the 930’s 3.3, not the new 3.6. Single turbo, rear-wheel drive, and the last of the old-school lag.

Known issues

5 Specific to the Turbo

Engine oil leaks

Critical $500–$12,000
Affects

All 964, and worst on the earliest cars.

What happens

The 964 leaks in ways other air-cooled 911s do not. Beyond the usual valve covers and return tubes, the early engines suffer at the cylinder head and case sealing surfaces, and putting that right properly means the engine out and apart. Porsche revised the sealing during the run, so later cars are better but not immune.

Symptoms
  • Persistent drips despite gaskets having been replaced
  • Oil soaking the engine tinware and heat exchangers
  • Burning smell after every drive
  • A seller describing it as "normal for an air-cooled car"
What to do

Establish the source before accepting any reassurance. Valve covers are routine; head and case sealing is an engine-out job that can approach the value of a cheaper 964. This single issue is the difference between a good car and a money pit.

Parts for this job

Dual-mass flywheel failure

Major $1,800–$4,000
Affects

All 964, early cars especially.

What happens

The dual-mass flywheel wears and its damping springs break down, producing rattle and eventually clutch problems. The original units were not durable and many cars have already been converted.

Symptoms
  • Rattle at idle that quietens when the clutch is depressed
  • Vibration through the pedal
  • Gear selection becoming notchy
What to do

Replace with the clutch, since the labour is shared. Many owners fit a single-mass conversion, which is more durable and noisier — a trade most 964 owners consider worthwhile.

Parts for this job

Valve guide wear

Major $8,000–$16,000
Affects

All 964.

What happens

Guides wear and let oil into the combustion chamber. It develops slowly and ends in a top-end rebuild.

Symptoms
  • Blue smoke on cold start or after a long overrun
  • Oil consumption with no matching external leak
  • Uneven leak-down figures across cylinders
What to do

No preventive fix. Insist on a leak-down test at inspection and treat a top end as a long-term budget item rather than a surprise.

Weak air conditioning

Minor $800–$3,000
Affects

All 964.

What happens

Marginal when new, and thirty-plus years of condenser corrosion and leaks have not helped.

Symptoms
  • Cooling only at speed
  • Nothing at idle in traffic
  • Repeated recharging
What to do

Uprated condensers and fans help. Expect improvement, not modern performance.

Parts for this job

Sunroof and electrical faults

Minor $200–$2,000
Affects

All 964.

What happens

The 964 added considerably more electrical complexity than the cars before it, and age tells: sunroof motors and cables, window regulators, the spoiler mechanism and central locking are all common complaints.

Symptoms
  • Sunroof binding or refusing to move
  • Rear spoiler not deploying at speed
  • Intermittent window or locking faults
What to do

Mostly individually cheap, collectively tedious. Operate every single electrical item during inspection — this is where deferred maintenance accumulates quietly.

Does not affect this car

Distributor drive belt failure — documented elsewhere in the 964 range but not applicable to the Turbo. See the generation overview for the full picture.

Service intervals

7
Item Interval
Engine oil and filter 5,000 mi or annually
Valve adjustment 15,000 mi
Brake fluid 2 years
Fuel filter 30,000 mi
Transmission and differential fluid 40,000 mi
Clutch and dual-mass flywheel 60,000–100,000 mi
Valve cover gaskets As leaks appear

What fits this car

29 Sizes, capacities and part specs

The answers you need when something has already failed — bulb sizes by position, wiper lengths, battery group, fluid specs and capacities. Sizes are for US-spec cars and are a starting point: options and mid-year changes move them, so check against your own car and its VIN before ordering.

Bulbs

8 US cars use the upright round headlamp with a replaceable H4 capsule.
Headlight — low and high H4 60/55W One capsule serves both filaments. Shop →
Front turn signal PY21W Amber. Shop →
Front position / parking W5W Shop →
Fog light H3 55W Shop →
Brake / tail P21/5W Shop →
Rear turn signal PY21W Shop →
Reverse P21W Shop →
Licence plate W5W Shop →

Wiper blades

2
Driver side 20 in Shop →
Passenger side 20 in Shop →

Battery

3
Group size Group 48 (H6) Shop →
Location Front luggage compartment, right side —
Minimum cold cranking amps 600 CCA —

Fluids and capacities

7 No coolant. The oil does the cooling as well as the lubricating, which is why there is so much of it.
Engine oil — capacity 12.7 qt with filter Dry-sump system with a separate tank. Check warm and running, per the factory procedure. —
Engine oil — specification 20W-50 or 5W-50, high-zinc Formulated for air-cooled flat-sixes. Not the place for a modern low-zinc oil. Shop →
Coolant None — air-cooled No radiators, no expansion tank, no coolant service. —
Brake fluid DOT 4 Shop →
Transmission — manual 75W-90 GL-5 Shop →
Power steering Pentosin CHF 11S Shop →
Fuel tank 20.3 gal —

Wheels and tyres

7
Bolt pattern 5 x 130 mm
Centre bore 71.6 mm
Lug bolt thread M14 x 1.5
Tyre size — 16 in front 205/55 ZR16
Tyre size — 16 in rear 225/50 ZR16
Tyre size — 17 in front 205/50 ZR17
Tyre size — 17 in rear 255/40 ZR17

Torque values

2 Safety-relevant. Verify against factory documentation before relying on these.
Wheel lug bolts 96 lb-ft (130 Nm) Star pattern, on the ground, calibrated wrench.
Engine oil drain plug 37 lb-ft (50 Nm) New sealing washer every time.

Fitment for the 1991 964 Turbo. Torque values in particular are safety-relevant — verify against factory documentation rather than relying on this page alone.

Buying guide

6
  1. 01

    Take the leak story seriously

    Every air-cooled 911 seeps. The 964 has failure modes that require the engine out to fix properly, and "they all do that" is how those cars get sold. Get it on a lift and establish the actual source before you agree a price.

  2. 02

    Leak-down test across all six

    Valve guide wear is developing on most of these by now. A leak-down test is how you find out whether you are buying a top end with a car attached.

  3. 03

    Operate every electrical item

    Sunroof, spoiler, windows, locks, air conditioning, lights. Individually cheap, collectively expensive, and this is exactly where deferred maintenance hides on a 964.

  4. 04

    Later is better

    Porsche revised the engine sealing and other details through the run. All else equal, a 1993 or 1994 car is a meaningfully lower-risk purchase than a 1990.

  5. 05

    C2 over C4 unless you need the traction

    The C2 is lighter, simpler, more engaging and cheaper to maintain. The all-wheel-drive system adds complexity that thirty years has not made easier to service.

  6. 06

    Buy the sorted one

    The gap between a 964 that has had its engine addressed and one that has not is larger than the price difference between them. Paying more for documented work is almost always the cheaper route.

Parts and gear

12 Chosen for this car, not for the commission

What a Turbo actually costs to keep, grouped by why you would buy it. Prices are typical US parts-only figures — labour is separate, and the DIY note says whether that matters. Where a link earns us a commission it costs you nothing and never changes what appears here.

Parts that fix a known problem on this car

3 Each one maps to an issue above
  • Engine $80–$320

    Valve cover gasket set

    The accessible end of the 964 leak problem. Worth doing early so that any remaining leak is genuinely diagnostic rather than lost in the noise.

    FCP Euro → DIY or shop
  • Drivetrain $1,200–$2,800

    Clutch and single-mass flywheel conversion

    The common answer to a failed dual-mass unit: more durable, audibly noisier at idle, and a trade most 964 owners make happily. Do it with the clutch or pay the labour twice.

    FCP Euro → Shop job
  • Cooling $700–$2,500

    Uprated A/C condenser and fan kit

    The established fix for a system that was never good. Buys usable air conditioning, not modern air conditioning.

    FCP Euro → Shop job

Worth doing before it fails

1 Cheaper than the repair it avoids
  • Engine $25–$60

    Magnetic drain plug

    Early warning at every oil change on an engine whose rebuild runs to five figures.

    Shop this → DIY

Consumables you will rebuy

4 Ordinary running costs
  • Fluids $80–$170

    Air-cooled specification engine oil

    Heavier weight and a high-zinc additive package suited to this era of hardware. Around nine to ten quarts a change, and the wrong modern oil is a false economy on an engine like this.

    Shop this → DIY
  • Fluids $20–$60

    Oil filter and sump hardware

    Bought with every change, and worth cutting open every time on this engine.

    Shop this → DIY
  • Fluids $15–$60

    Brake fluid

    Two-year replacement. The cheapest safety-relevant service the car has.

    Shop this → DIY
  • Service $40–$130

    Air and fuel filters

    Routine owner jobs on this generation, and both are heavily marked up when a shop does them.

    Shop this → DIY

Tools worth owning

4 Bought once, used for years
  • Inspection $60–$250

    Leak-down tester

    Finds valve guide wear before you own it. If you are shopping several 964s it pays for itself on the first car you walk away from.

    Shop this → DIY
  • Inspection $30–$80

    Oil filter cutter

    Cheap insight into an engine that is expensive to open.

    Shop this → DIY
  • Lifting $150–$400

    Low-profile jack and jack pads

    You will be under this car looking for the source of a leak more than you expect. Do it safely and without crushing the jack points.

    Shop this → DIY
  • Storage $100–$500

    Battery tender and car cover

    These sit more than they run, and a 964 with damp and a flat battery finds new electrical faults to show you.

    Shop this → DIY