Formulas and Tables

DISPLACEMENT OF EVOLUTION ENGINES:

    STROKE
BORE
3.498 3.625 3.780
Stock 80” S & S Sputhe
3.812 Sportster 73.268 78.685 85.557
4.250 Stock 80” 81.686 87.725 95.388
4.625   88.894 95.466 103.805

CALCULATING THE DISPLACEMENT OF A TWO CYLINDER ENGINE:

       Displacement can be determined by the formula: D = B X B X S X 1.5708

Where: D = Displacement
  B = Bore
  S = Stroke

CALCULATING COMPRESSION RATIO:

Compression ratio can be determined by the formula:

C = D + Vd + Vs + Vc
      Vd + Vs + Vc

 

Where: C = Compression ratio
  D = Displacement of one cylinder
  Vd = Volume of dish (+) or dome (-) on piston
  Vs = Volume of squish clearance
  Vc = Volume of combustion chamber

To calculate the compression ratio of an engine using Sputhe cylinders the following values may be used.

D = 782cc for the 95.4” kit D = 850cc for the 103.8” kit
Vd = 16cc for dish top pistons Vd = 0cc for the flat top pistons
Vs = 11cc @ .060” clearance  
Vc = 78cc for pre 1990 heads Vc = 87cc for 1990 & up heads

Example: 1989 engine using a 95.4 ci kit with dish top pistons:

C = D+Vd+Vs+Vc= 782cc+16cc+11cc+80cc= 897cc = 8.54
   Vd+Vs+Vc     166cc+11cc+80cc 105cc   1

 

FORMULAS FOR CALCULATING TORQUE & HORSEPOWER:

T = Hp X 5252 Hp = T X rpm
      Rpm     5252

TABLE OF EQUIVALENTS:

1 inch = 25.4 mm 1 cubic inch = 16.387cc
1 mm = 0.039371 inch 1 liter (1000cc) = 61.024 cubic inch

 

MECHANICAL COMPRESSION RATIOS
OF SPUTHE BIG BORE CYLINDERS

95 cu inch – Compression Ratios  

CHAMBER FLAT TOP PISTONS DISH TOP PISTONS
90cc 8.7:1 7.7:1
86cc 9.0:1 7.9:1
80cc 9.6:1 8.3:1
76cc 10.0:1 8.6:1
72cc 10.4:1 8.9:1

 104 cu inch – Compression Ratios 

CHAMBER FLAT TOP PISTONS DISH TOP PISTONS
90cc 9.4:1 8.3:1
86cc 9.8:1 8.5:1
80cc 10.3:1 8.9:1
76cc 10.8:1 9.3:1
72cc 11.3:1 9.6:1

 Piston Balance Weights 

95 cu inch – 3.780 Standard bore Flat Top Pistons – 1057 grams
Dish Top Pistons – 1061 grams
104 cu inch – 3.780 Standard bore Flat Top Pistons – 1042 grams
Dish Top Pistons – 1039 grams

 

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Tel: +1 (530) 268-0887 

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Grass Valley CA 95945

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