Buyer’s guide: Porsche 928

By Malcolm McKay

| 14 Apr 2022

Classic & Sports Car – Buyer’s guide: Porsche 928

Why you’d want a Porsche 928

Porsche’s advertising spiel stated: ‘More thought has gone into the design and creation of the dramatic 4.5-litre Porsche 928 V-8 luxury sports coupé than perhaps any other car ever made. More technical innovation. More engineering skills. Which all moved an august body of international motoring journalists to vote the 928 Car of the Year 1978.’

It was a well-deserved win, an extremely rare one for a sports car, and the 928’s clean lines have aged well.

There was no denying the family resemblance to the bottom-of-the-range 924, which may have confused the market because the 928 cost more than the 911, with only the 911 turbo above it.

The rear seats were limited for both leg- and headroom – ideal for children, but only suitable for short trips with adults.

Like its smaller sister, the 928’s engine was set well back and balanced by a transaxle, linked to the engine by a torque tube.

The engine was an all-new, all-alloy V8 with hydraulic tappets and fuel injection, initially happy to run on 95-octane fuel and producing 240bhp, but clearly with potential for much more. Flexibility and docility were its key characteristics, rather than exceptional performance.

Frustratingly, the V8 was muted in operation, with no characterful burble, but wind and especially tyre noise meant that the 928 was not the silent sports car it could have been.

It was a confusing mix for some, with suspension oriented more towards great handling than ultimate ride, but with progressive development performance went from impressive to outstanding, with refinements in all areas that made the 928 more and more a world-beating, mile-eating supercar – and priced accordingly.

Through production, the 928 ultimately gained more than 100bhp, a 42% increase. Road testers always chose the manual, but some 80% of cars had the Mercedes-Benz-sourced automatic.

Electronics were state of the art, with twin flashing dash warning lights for major faults and cancellable flashed warnings for lesser faults.

Cruise control and air-con were standard and the impressive heater included door-mounted vents.

A six-year anti-corrosion warranty on the galvanised body was extended to 10 years in 1986: they do rust, but rarely severely – yet.

A comprehensive service history is desirable; check the spec on the sticker in the service book and on the boot floor, which has precise model codes, though both are often lost.

Images: James Mann

Porsche 928: what to look for

Trouble spots

See above for what to check when looking at Porsche 928s for sale.

Engine

‘Spider’ intakes dominate the all-alloy V8 engine in final single-cam-per-bank form.

Well-maintained engines should exceed 150,000 miles without a rebuild, but watch oil consumption and four-year/60,000-mile cambelt intervals (check the history to confirm that tensioners and water pump were changed, too).

Radiator

Check the radiator (here with air-con cooler in front) for leaks and rust – a new one can exceed £1000.

Bills for regular coolant swaps are a good sign.

Electrics

Complex electronics will play up with age and neglect – though rough-running may just be down to a failed drive belt between the distributors.

Suspension

Suspension bearings and bushes wear with age and miles, as do dampers, resulting in woolly handling.

Look out for rust in subframes and mountings.

Interior

Early cars had half-leather or vinyl trim with ‘Pasha’ chequered velour centres: it’s desirable now, but most buyers preferred later full leather.

Porsche 928: before you buy

On a well-maintained engine, expect to rebuild the cylinder heads at around 120,000 miles and the bottom end beyond 150,000.

Look for oil smoke on start-up and on the overrun indicating that at least a top-end overhaul is needed. Any fore/aft movement on the crankshaft needs urgent major work.

Head bolts replaced studs on the S4: it’s easier to lift the heads with the engine in situ but in some cases head cracking ensued, cured for 1989 with a thicker casting and longer bolts.

Look for signs of oil/water mixing on all cars, but especially 1986-’89 S4s. Issues with 1987-on LH-Jetronic 2.3 injection ECUs, EZK ignition and mass airflow sensors are common; specialists such as JDSPorsche offer remedies. The main fuseboard, relays and ECUs are in the passenger footwell.

Check the VIN, engine and option codes, especially on top-spec cars, and be wary of engine swaps: many US cars had considerably less power.

The transmission was steadily updated, especially the manual which had multiple changes to the clutch, gearbox and torque tube.

The clutch was twin-plate at first, changing to single-plate on the S4. Manuals are rare (c20% of production) and command a 10-20% price premium if you can find one.

Brakes and suspension were also regularly updated and improved through the years. Passive rear-wheel steering was provided by the ‘Weissach Axle’ arrangement, which minimised understeer.

Alloy wheels changed in size and style several times – note that the wheel offset is unique to the 928.

Porsche 928 price guide

Restoration/average/show

SE, CS: £25,000/55,000/125,000*
GTS: £10,000/31,000/60,000*
GT: £8000/23,000/50,000*
S4: £5000/15,000/35,000*
928, S, S2: £3000/12,500/32,000*

^{*Prices correct at date of original publication}

Porsche 928 history

1977 Mar Geneva launch, on sale September

1978 Voted Car of the Year; UK sales Oct

1979 Sept Auto option; 4.7-litre 928 S with 300bhp, spoilers, better brakes, electric seats

1981 Sept Weissach edition for USA (200+ built), 50th Jubilee for RoW (141, LHD only)

1982 Sept 4.5-litre dropped

1983 Sept S2: optional ABS, four-speed auto

1984 S3 (US): quad-cam, catalytic converter

1986 Oct S4: restyled nose, 5.0 quad-cam V8

1988 Mar Uprated Club Sport (EU/US, 17 built) or S4 Sport SE (UK, 42 built)

1989 Feb GT replaces CS/SE

1991 Sept GTS replaces S4/GT: restyle, 5.4 V8

1995 Aug 928 production ends

The owner’s view

Ian Bramble bought his 1978 S1 in 2002: “I’d always wanted a V8, and when I read about the 928 in Motor Sport in 1978 it became my dream car.

“Mine had done 78,000 miles and wasn’t in good shape, but the oil pressure was fine, it had matching numbers and it drove well.

“I de-rusted the underside, then painted it with two-pack. It’s lasted well, but is currently in the body shop after my local garage bumped it.

“I’ve replaced the rear lower control arms and dampers, dropped the ’box to change an oil seal, replaced the sump gasket, removed the binnacle to swap the odometer drive, changed the clutch and replaced the water pump, cambelt and crank seals.

“The next jobs are sorting a misfire and a water leak from the thermostat. I’ve done most of the work myself and thoroughly enjoy driving the car: it’s now on 122k and still goes very well.”

Also consider

Mercedes’ SEC (left) and Jaguar’s XJ-S are alternative buys

JAGUAR XJ-S

Amazing value for money, the XJ-S in V12 form was a great all-rounder at first, but barely improved while the 928 got much better over the years. Rust and neglect are the main enemies.

Sold 1975-’96 • No. built 115,413 • Price now £6-50,000*

MERCEDES-BENZ SEC

Great build quality, with a range of V8s from 3.8 to 5.6 litres, and a superb, spacious cruiser, but the handling is no match for a 928. Beware localised but inaccessible rot, and parts prices.

Sold 1979-’91 • No. built 74,060 • Price now £2500-150,000*

^{*Prices correct at date of original publication}

Porsche 928: the Classic & Sports Car verdict

Decades of inattention due to high maintenance costs, low values and scrimping owners have taken their toll on most Porsche 928s – there are still some fabulous cars out there, but you will have to work harder than ever to find a good one.

Top-spec cars, always sought-after, are likely to have been better cared for but can be a lot more expensive.

A good 928 is a very usable everyday supercar – and still great value.

FOR

Enormously rewarding yet a relaxed tourer, a well-maintained 928 should be reliable and worry-free
Specialists have solutions to most faults, often more affordable than you’d expect

AGAINST

Past neglect can cost far more to put right than the ultimate value of this complex classic

Porsche 928 specifications

Sold/number built 1977-’95/61,056
Construction galvanised steel monocoque, aluminium doors, bonnet and front wings
Engine all-alloy, ohc 4474/4664cc V8, or 4957/5397cc dohc V8, with Bosch injection; 240bhp @ 5500rpm-350bhp @ 5700rpm; 257lb ft @ 3600rpm-362lb ft @ 4250rpm
Transmission five-speed ZF manual or three/four-speed automatic, RWD
Suspension: front double wishbones rear upper transverse links, lower wishbones; coil springs, telescopic dampers, anti-roll bar f/r
Steering power-assisted ZF rack and pinion
Brakes vented discs, with servo
Length 14ft 7-10in (4445-4519mm)
Width 6ft ¼-¾in (1836-1849mm)
Height 4ft 2½-3¾in (1282-1316mm)
Wheelbase 8ft 2½in (2500mm)
Weight 3237-3520lb (1471-1600kg)
Mpg 14-24
0-60mph 7.0-5.4 secs
Top speed 140-170mph
Price new £21,827/25,250 (4.5/S, 1981)