Rover P5B Coupé: identity, V8 and modifications supplement (1967 to 1973)

The P5B, sold by Rover as the 3.5 Litre, was the final version of the P5 saloon and coupé that had been in production since 1958. It arrived in September 1967 when Rover replaced the 3 litre six-cylinder engine with the all-alloy V8 it had developed from a General Motors design originated by Buick; the "B" in the internal name refers to Buick. The coupé body, first seen in 1962, kept four doors and the saloon's length and width but had a roofline lowered by about two and a half inches and slimmer pillars. The P5B was automatic only, with power steering and front fog lamps as standard, and it remained a favourite of government ministers until production ended in 1973.

This supplement does not repeat a general buying guide. It concentrates on four questions that come up often with P5B coupés: how to tell a genuine P5B from a 3 litre car, what the Rover V8 brings, how to judge common modifications such as a later 4.6 litre V8 or an aftermarket sunroof, and how such changes should be reflected on the V5C after DVLA's August 2025 policy changes.

• Production: 1967 to 1973; Classic & Sports Car gives 9,099 coupés and 11,501 saloons, a total of 20,600.
• Whole P5 family production: 69,141 according to Wikipedia and Swedish Rover club statistics.
• Engine: 3,528cc Rover V8, overhead valves, light alloy.
• Power: sources quote 160 bhp, 161 bhp or 160 PS; torque is given as 210 lb ft.
• Transmission: Borg Warner Type 35 three-speed automatic only.
• Standard equipment: Hydrosteer variable-ratio power steering, Lucas fog lamps, chromed Rostyle wheels.
• Preceding model: P5 3 litre Mark III (1965 to 1967), 134 bhp, available with manual or automatic gearboxes.

• The Mark III 3 litre introduced individual rear seats and a full-length side trim strip, which the P5B carried over, so trim alone does not separate the two.
• Visible P5B identifiers are 3.5 Litre badging, twin fog lamps below the headlamps giving a four-lamp front, and chromed Rostyle wheels with black inserts.
• Mechanical identifiers: the P5B uses a mechanical fuel pump where earlier cars had an electric one, and it was never offered with a manual gearbox, so a car with a factory clutch pedal is a six-cylinder car.
• Earth polarity changed over the life of the P5 family. A buying guide notes that alternator cars are generally negative earth, but advises checking.
• Engines were designed for five-star fuel and ignition timing usually needs retarding from handbook settings for modern petrol.

Identity and paperwork

• Check the chassis plate and the V5C. The V5C should describe the car as a 3.5 litre with a cylinder capacity of about 3,528cc, unless an engine change has been notified. A V5C showing about 2,995cc on a car with a V8 suggests a 3 litre that has been converted.
• No reliable published key to P5B chassis number prefixes was found for this guide. The Rover P5 club or a marque specialist should be asked to confirm that the chassis number belongs to a 3.5 Litre coupé.
• Look for signs of a converted 3 litre: traces of a clutch pedal or manual linkage, an electric fuel pump fitted where the P5B used a mechanical one, Mark III badging, and wiring or mountings that do not suit a V8. Note that some genuine P5Bs have been converted to electric pumps.

The Rover V8 and later capacities

• The Rover V8 was built in 3.5, 3.9, 4.0, 4.2 and 4.6 litre forms, the 4.6 being a fuel-injected engine used in the P38 Range Rover. A 4.6 in a P5B is therefore a much later engine, and a swap may bring different induction, ignition and engine management from the original carburettor set-up.
• Ask who did the swap, what gearbox and cooling changes were made, and whether the original 3.5 engine is retained. One owner's account in Practical Classics describes a modified P5B coupé with a replacement gearbox for more relaxed cruising, uprated cylinder heads and a different carburettor and manifold, and stresses specialist help and quality parts. Expect to find similar combinations of changes rather than an engine swap alone.
• On any V8, check that the coolant contains at least half antifreeze to protect the alloy waterways, that tappet noise fades as the engine warms, and that there is no sign of overheating. A missing thermostat can hide a cooling problem.
• Automatic fluid should be bright red; brown or black fluid suggests attention is due.

Sunroofs

• If a folding fabric sunroof of the Webasto type is fitted, ask when and by whom. No source was found that confirms whether such a roof was ever a factory option on the P5B, so treat it as an aftermarket addition unless documents say otherwise.
• Check the fabric, the frame and the roof around the aperture for rust and leaks, and look for water staining on the headlining. Owners of other marques report that new Webasto spares are no longer available and that refurbishment relies on specialist trimmers.

How a modification should appear on the V5C

• Changing the engine for one of a different capacity changes the V5C details and must be notified. DVLA asks for a receipt showing the new engine number and capacity, written evidence from the manufacturer, an insurance inspection report, or a garage letter on headed paper if the change pre-dates the current keeper. Capacity changes go to a separate DVLA address from other changes.
• Under DVLA's 2025 guidance, like-for-like repairs do not need reporting, but a structural modification that cuts into the bodyshell and changes its appearance or dimensions must be notified on form V627/3, and the V5C will then carry a "Modified" note. The leaflet does not mention sunroofs specifically; ask DVLA or the club if a sunroof cut-out raises a question.
• For MOT exemption, the government criteria treat alternative capacities of the same basic engine as not being a substantial change. Whether a later 4.6 Rover V8 counts as the same basic engine as the 3.5 is a judgement the criteria do not settle, so ask the seller what declaration has been made.

Body checks specific to the coupé

• Check sills, which are structural, the rear valance, inner front and rear wings, battery trays and the base of the A-posts. Buying guides advise walking away from serious corrosion at the A-post to sill joint.
• Check the Rostyle wheels for pitting and kerb damage.

Directories list the Rover P5 Club at http://www.roverp5club.org.uk/; the same address is listed elsewhere as the Rover P5 Owners Club, founded in 1985, and Companies House holds an active company called Rover P5 Club, incorporated in 2004. The club website could not be opened for this guide, so confirm the current name and services directly. Buying guides describe strong club and specialist support, with door handles, gauges, trim and carpet sets available; brake parts are reported to be scarcer. The Rover V8 was used across Rover, Land Rover, MG, Triumph, TVR and Morgan models, so many engine parts are shared with far more common vehicles.

• Does the chassis number confirm a factory 3.5 Litre coupé, and has the club checked it?
• What engine is fitted now, and does the V5C show the correct cylinder capacity?
• If a 4.6 or other non-original V8 is fitted, what evidence of the change was sent to DVLA, and is the original engine with the car?
• Was the sunroof fitted from new or later, and has it ever leaked?
• Has any structural modification been notified on a V627/3, and does the V5C show a "Modified" note?