Merak SS Engine

From Citroen SM Wiki

A well-known upgrade is to install a Merak SS engine. It is rated at 220 BHP, which it achieves at higher RPM. At low RPM it's similar in character to an 3.0L SM engine.

Engine Differences

Engine Specs

  • (from 1974 Merak SS)
  • Bore × stroke 91.60 mm × 75.00 mm
    • 3.61 in × 2.95 in
  • Displacement 2965 cc
    • (180.935 cu in)
  • DOHC
  • 2 valves per cylinder
  • Compression ratio 9.00:1
  • 3 Weber carbs
  • Maximum power
    • (DIN) 210.9 PS (208.0 bhp) (155.1 kW) @ 5800 rpm - Maserati handbook states 220 bhp DIN
  • Specific output 70.2 bhp/litre, 1.15 bhp/cu in
  • Maximum torque
    • (DIN) 255.0 Nm (188 ft·lb) (26 kgm) @ 5000 rpm
  • bmep 1080.8 kPa (156.7 psi)
  • Specific torque 86 Nm/litre
  • Main bearings 4
  • Bore/stroke ratio 1.22
  • Unitary capacity 494.17 cc/cylinder


  • The Merak SS engine, Maserati C 114.55.30 and C 114.63.30 is completely different to the standard 3 litre SM engine, though externally appearance is very similar.
  • The only shared parts are:
    • timing chains
    • bearings, gaskets (except the water pump seal and valve cover gaskets)
    • sleeves
    • nuts and bolts
    • camshafts
      • Same as 3.0/IE engines
  • The SS engine serial number starts with 520.000 or 610.000.
  • The early engines used a hydraulic assist to the original Renold tensioner
(this was on engine number 610.008).
  • The hydraulic tensioner started around number 610.113.
  • The difference between 114.55.30 engines and C114.63.30 is the lightening holes in the hydraulic tensioner.
  • The early versions up to 610.150 use hydraulic tensioners with holes in them
    • Later engines (David Hume seen numbers up to 610.645) have no holes.
  • Basically the SS engine has bigger valves and heads that flow 20% better than the stock SM 3 litre ones.
  • The cam lift is more radical and the pistons are more domed for due to the larger bowl in the head.
  • The other huge change is the oil circuit it is completely different.
    • Maserati was trying to stop the oil from centrifuging in the crank shaft by splitting the main oil journal in the crank behind the oil pump and making the oil go two places instead of one.
  • Valve covers had six bolts, not 5 in the SM.

Notes on the conversion

To fit the engine, the only addition to the car is the correct carburettors (possibly come with the engine) and 'big bore' exhaust manifold parts as both tubing and mounting hole spacing is larger.