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Technical Calculator

Height Compression

Get accurate calculations for compression height by entering the Block height, Crank stoke, Rod length, and Deck clearance in the required fields of the calcualtor.

The height compression calculates the compression height which is the distance from the pinhole to the deck of the piston. Get accurate measurements in terms of inches and meters with this tool.

What Is Piston Compression Distance?

The piston height compression is the dimension or the distance from the flat top of the piston to the center of the piston pin. 

The piston compression distance is also referred to as the piston pin height to avoid confusion. The piston compression distance is adjusted relative to the required efficiency of the engine. The precise person compression height increases the efficiency of the engine at a high speed.

How to Determine Compression Height?

The compression height is the distance between the center of the wrist pin to the crown of the piston.

For calculating the piston compression height, use the following formula:

Piston compression height =BH-(½)CS-RL-DC

Or 

CH=BH−.5∗CS−RL−DC

Where:
  • CH is the compression height
  • BH is the block height
  • CS is the crank stroke
  • RL is the rod length
  • DC is the deck clearance

Practical Example:

Let the block height is 6 inches, the crank stone is 3 inches long, the rod length of the engine be 1.5 inches and the deck clearance is 2 inches. Then calculate the piston compression distance.

Solution:

We know the compression height person's formula

CH = BH – .5*CS – RL – DC

Insert the values in the above formula 

CH = 6- .5*3 – 1.5 – 2

Then 

CH = 1inch

CH = 0.0254 m

The piston compression distance is 1 inch or 0.0254 m.

Size of the Compression Piston:

There are three things you need to decide when deciding the size of the piston.

  • The Block Height
  • The Connecting Rod Length
  • The Stroke Length

The Block Heights:

The block height is measured from the crankshaft to the centerline of the deck.

 

Compression Height

Displacement Cubic Inches Liters Deck Height (inches)
302 4.9 9.025
305 5.0 9.025
327 5.4 9.025
350 5.7 9.025
350(LT5) 5.7 9.025
350(LS1) 5.7 9.240
364(LQ4) 6.0 9.240
383 6.3 9.025
400 6.6 9.025
396 6.5 9.800
402 6.6 9.800
427 7.0 9.800
454 7.4 9.800
502 8.2 9.800

The Connecting Rod Lengths:

The Connecting rod length is measured between the centers of the big end and the little end.

 

Rod Length

Displacement Cubic Inches Liters Big End Dia. (inches) Rod Length (inches)
302 4.9 2.1000 5.7000
305 5.0 2.1000 5.7000
327 5.4 2.1000 5.7000
350 5.7 2.1000 5.7000
350(LT5) 5.7 2.1000 5.7400
350(LS1) 5.7 2.2500 6.0980
383 6.3 2.1000 6.0000
400 6.6 2.1000 5.5650
396 6.5 2.2000 6.1350
402 6.6 2.2000 6.1350
427 7.0 2.2000 6.1350
454 7.4 2.2000 6.1350
502 8.2 2.2000 6.1350

The Stroke Length:

The stroke length is twice the distance from the centerline and the crankshaft.

 

Stroke Length

Displacement Cubic Inches Liters Bore (inches) Stroke (inches)
302 4.9 4.000 3.000
305 5.0 3.740 3.480
327 5.4 4.000 3.250
350 5.7 4.000 3.480
350(LT5) 5.7 3.898 3.661
350(LS1) 5.7 3.898 3.622
364(LQ4) 6.0 4.000 3.622
383 6.3 4.000 3.800
400 6.6 4.125 3.750
396 6.5 4.094 3.766
402 6.6 4.125 3.766
427 7.0 4.250 3.766
454 7.4 4.250 4.000
502 8.2 4.470 4.000

 

Working of this Calculator:

Let's have a look at the simple working of the piston compression distance:

Input:

  • Enter the Block height, Crank stoke, Rod length, and Deck clearance in their respective fields
  • Tap Calculate 

Output:

  • Height Compression

FAQs:

What Are the Benefits of High Compression of Pistons?

Higher compression allows for a larger amount of fuel/air mixture to be successfully combusted and you can generate more power by the larger piston compression distance.

References:

From the source of Wikipedia: Height compression human.