Those Dyno Guys Compression calculator built by Matt Smith

Warning-Calculations are for reference only. Builder must verify actual measurements and Specifications

Step 1 — Engine

Pick Engine Size

Choose a preset or leave Custom selected and enter bore and stroke manually.

Bore inches

Cylinder bore size.

Stroke inches

Crank stroke length.

Rod Length inches

Rod length measured center to center.

Engine Displacement calculated

Cubic inches 0.0

CC 0

Step 2 — Gaskets, Deck & Head

Head Gasket Thickness inches

Head gasket thickness at final torque.

Head Gasket Bore inches

Usually about 0.030" larger than cylinder bore.

Base Gasket Thickness inches

Pick your base gasket stack from the list or leave Custom and enter your measured thickness.

Cylinder Head Volume cc

Pick your head style from the list or leave Custom and enter your measured chamber volume.

Deck Height — Front inches

Enter a positive number if the piston is below deck.

Deck Height — Rear inches

The calculator uses the average of front and rear.

Step 3 — Piston & Top Ring Land

Piston Dome / Dish Volume cc

Positive dome reduces volume. Negative dish adds volume.

Optional Piston Diameter inches

Measure piston diameter above the top ring. Leave 0 to ignore this.

Optional Top Ring Land Height inches

Distance from piston crown to the top ring. Leave 0 to ignore this.

Step 4 — Cam & Altitude

Choose Cam

Pick a cam or leave on manual and type the intake closing angle.

Intake Close ABDC degrees @ 0.050

Filled automatically from the cam list or enter your own value.

Altitude feet above sea level

Used to correct compression and estimate cold cranking pressure.

Cam timing offset degrees (advance +, retard -)

Use this to see what happens if you advance or retard the cam a few degrees. Positive numbers advance the cam (earlier close). Negative numbers retard it (later close).

Adjusted intake close degrees ABDC

Effective closing angle after any cam timing offset is applied.

Results

Static Compression 0.00 : 1

Corrected / Dynamic Compression 0.00 : 1

Cold Cranking Compression 0 psi

Altitude Label @ Sea Level

Twin Cam Cam Compare

Pick up to three Twin Cam / Evo cams, compare intake-close angles, then send one into the calculator.

Cam A

Cam B

Cam C

Spec	Cam A	Cam B	Cam C
Cam name	—	—	—
Intake close (°ABDC)	—	—	—

M8 Cam Compare

Pick up to three M8 cams, compare intake-close angles, then send one into the calculator.

Cam A

Cam B

Cam C

Spec	Cam A	Cam B	Cam C
Cam name	—	—	—
Intake close (°ABDC)	—	—	—

Values are approximations. Use actual measured values when available. Calculator supplied as an engine building aid only.