Outils moteur — joints, conversions & jeux de fonctionnement

Gasket thickness calculator (target = desired CR)

Assumption: V_joint = π/4 × (gasket bore)² × (thickness). Convention volume piston : plat = 0, cuvette = positif, dome = negative.

Cylinder bore mm Stroke mm Gasket bore mm Deck clearance (deck height) mm Volume chambre culasse cc Piston volume (+ dish / − dome) cc Desired CR (e.g. 10.0) Minimum safe thickness (optional) mm

Formulas used

Vd (per cylinder) = π/4 × bore² × stroke / 1000
Vdeck = π/4 × bore² × deck / 1000
Vgasket = π/4 × gasketBore² × thickness / 1000
Vcl (without gasket) = Vchamber + Vpiston + Vdeck
CR = (Vd + Vcl + Vgasket) / (Vcl + Vgasket)
⇒ Required thickness = ( Vtarget − Vcl ) × 1000 / ( π/4 × gasketBore² )
where Vtarget = Vd / (CR − 1)

Glossary & units

Bore (mm) : cylinder diameter.

Course (mm) : total piston travel.

Deck height (mm) : distance to TDC between block face and crown (edge).

Volume chambre / piston (cc) : measured with a burette.

Workshop unit converter

Longueur : mm ⇄ inch

Pression : bar ⇄ psi

Temperature: °C ⇄ °F

Volume : cc ⇄ in³

Couple : N·m ⇄ daN·m

Specific pressure: MPa ⇄ bar

Running clearance calculator (mains / crank pins)

Two approaches: (A) “Attelages mobiles des moteurs rapides” (reference book), (B) practical rule (k·D).

Vitesse de rotation N tr/min Shaft diameter D mm

Formules & remarques

(A) Book formula:  clearance (mm) = ( N^0.5 × D^2.5 ) / ( 460 × 10^5 )
(B) Approximate:      clearance (mm) ≈ k × D, k ≈ 0.00075 → 0.0010 (middle ≈ 0.00090)
      

Volumes de piston & rapport R/L

A) Volume de calotte/cuvette

Geometry

Signe (convention)

B) Rapport R/L & vitesse piston

Longueur de bielle L mm Course S mm Engine speed (optional) N tr/min

Camshaft timing diagrams (IVO, IVC, EVO, EVC)

Enter the angles “at the seat”. The calculation returns intake/exhaust durations, overlap (recouvrement au PMH), ICL/ECL (cam centres) and LSA (lobe separation angle).

AOA — Avance ouverture admission ° BTDC RFA — Retard fermeture admission ° ABDC EVO — Exhaust valve opening advance ° BBDC EVC — Exhaust valve closing retard ° ATDC Camshaft offset (optional) ° vilebrequin

Formulas & definitions

Intake duration (° crank)    DI = 180 + IVO + IVC
Exhaust duration (° crank)  DE = 180 + EVO + EVC
Overlap      OV = IVO + EVC

Intake centre line (ICL, in ° ATDC):
  ICL = (180 + IVC − IVO) / 2

Exhaust centre line (ECL, in ° BTDC):
  ECL = 180 − ( (180 − EVO + EVC) / 2 )

Lobe Separation Angle (LSA, °):
  LSA = ( ICL (ATDC) + ECL (BTDC) ) / 2

Cam offset (advance + / retard −, in ° crank):
  IVO' = IVO + Δ ; IVC' = IVC − Δ ; EVO' = EVO + Δ ; EVC' = EVC − Δ
      

About these engine calculators

These online tools are intended for enthusiasts and engine builders working on classic Renault engines (R5 Alpine, R5 Turbo, Clio Williams, Alpine A310, etc.) but also on other sports engines. They allow you to simulate the compression ratio, size the cylinder head gasket thickness,
calculate bearing running clearances ou encore d’evaluate the volume of a domed or dished piston.

L’onglet Gasket thickness helps determine the right compromise between compression and reliability, taking into account the chamber volume, the piston and the deck height.

The recommended press fit of 0.1 mm is advised for installation unit converter makes it easy to switch between mm/inch, bar/psi, N·m/daN·m, useful for interpreting workshop manuals or foreign documentation.

L’onglet Jeux de fonctionnement offers two methods for calculating bearing clearances (book formula Attelages mobiles des moteurs rapides and practical rule), to compare theory and practice.

Enfin, Volumes piston & R/L lets you quantify the volume of a piston dome or dish and calculate the rod/stroke ratio (R/L),
essential for analysing side loads and mean piston speeds.

By centralising these calculators on Mespiecesauto, we provide practical tools
for engine restorations and builds, with reliable technical content. Mespiecesauto declines all responsibility for the use of these tools. The manufacturer's instructions always take precedence over any external calculation