TVR Speed Six engine guide
The Speed Six is TVR’s in-house inline-six, developed alongside the AJP8 V8. It first appeared in the Cerbera and went on to power the Tuscan, Tamora, T350 and Sagaris. This page summarises the engine’s architecture, the power figures fitted to each model, the well-known reliability traps, and a sensible maintenance approach.
There is already a short overview at engines/speed-six; this page focuses on practical reference data and ownership guidance.
Architecture
Section titled “Architecture”The Speed Six is a slant-mounted inline-six with an all-aluminium block and head, twin overhead cams, four valves per cylinder and dry-sump lubrication.
| Item | Specification |
|---|---|
| Layout | Inline-6, slant-mounted |
| Valvetrain | DOHC, 24 valves (4 per cyl), finger followers |
| Block & head | Aluminium alloy |
| Displacement | 3,996 cc |
| Bore × stroke | 96 mm × 92 mm |
| Compression ratio | 12.2:1 (Sagaris spec) |
| Lubrication | Dry sump |
Power outputs by model
Section titled “Power outputs by model”Figures vary with state of tune; the values below are the commonly quoted factory ratings.
| Model | Power | Torque |
|---|---|---|
| Cerbera Speed Six | 350 hp @ 6,800 rpm | 330 lb·ft @ 5,000 rpm |
| Tuscan | 350–400 hp (varies) | — |
| Tamora | 350 hp | — |
| T350 | 350 hp | — |
| Sagaris | 406 hp @ 7,000 rpm | 349 lb·ft @ 5,000 rpm |
Known weaknesses
Section titled “Known weaknesses”Early Speed Sixes earned a reputation for fragility and a great many have been rebuilt at least once. The recurring failure modes are:
- Camshaft lobe wear. Early cams chewed themselves up; revised camshafts and follower designs were introduced and are normally fitted at rebuild.
- Finger follower wear. Flat-spotting and pitting on the followers is closely linked to the camshaft issue. Uprated followers are available from the established TVR specialists.
- Head gasket failure. Not unusual at higher mileages, often showing as oil/water cross-contamination.
- Valve seat recession. Symptoms are loss of compression and poor running; sometimes accompanied by valve clearances closing up.
- Water pump failure. A weak point. A failed pump quickly cooks the engine and can take the head gasket with it.
- Oil pump drive failure. Loss of oil pressure on a high-compression dry-sump six is catastrophic — inspect/replace at rebuild and watch the gauge in service.
Maintenance approach
Section titled “Maintenance approach”Owners generally service these engines far more aggressively than TVR’s original schedule suggested.
| Task | Interval | Notes |
|---|---|---|
| Engine oil & filter | 3,000 miles | A quality 10W-60 is the common owner choice |
| Valve clearance check | 12,000 miles | Shim-under-bucket; have spare shims to hand |
| Coolant | 2 years | Inspect water pump and hoses at the same time |
| Belts & fluids | Each service | Visual inspection of drive belts and all fluid levels |
Because oil pressure and clean oil are critical to cam and follower life, the short oil-change interval is the single most important habit to adopt. Always verify torque figures and clearances against the workshop manual for the specific model and engine variant before doing any work.
Rebuild notes
Section titled “Rebuild notes”A full Speed Six rebuild is typically in the region of £3,000–£6,000 depending on parts and specification. Established specialists include Str8six, Powers Performance and TVR Power. It is usual to fit the latest-spec camshafts and followers during a rebuild rather than reusing original parts.
Cerbera-specific service parts
Section titled “Cerbera-specific service parts”Useful cross-references for the Cerbera Speed Six (always confirm against your own car before ordering):
| Item | Part / cross-reference |
|---|---|
| Spark plugs | NGK DCPR8E |
| Crank position sensor | Ford 6859701 |
| Lambda sensor | Intermotor 16339 / Land Rover ERR 6729 |
| MAP sensor | Intermotor 16800 |
| Coil packs (×2) | 1996 Citroën ZX 1.6i |
| Starter motor | Bosch 0 001 108 063 / BMW 1 312 104 8 |
| Expansion tank | Audi 100 / A6 — 4A0 121 403 |
| Expansion tank cap | VW V443 121 321 |
Cautions
Section titled “Cautions”The Speed Six runs high compression and depends entirely on oil pressure and cooling for survival. Do not skimp on oil quality or change intervals, do not ignore a warm-running or low-pressure engine, and have any cam/follower or head gasket work done by someone who knows these engines. For safety-critical work, torque to the manufacturer’s spec and consult a marque specialist if in any doubt.
Compiled from community knowledge and owner forum write-ups — always verify against the relevant TVR workshop manual and a qualified specialist before relying on it.