Automotive Conversions You Need to Know

4WAAM-Slide-Rule-Conversions

Need to figure out how much a gallon of gas weighs? How about metric to SAE, or what displacement that junk yard engine you found is? Check out our handy conversions, 38 in total, to make it easy to figure all this out.

Quick Conversions

Ounces vs. Grams: 1 ounce = 28.35 grams
Pounds vs. Grams: 1 pound = 453.6 grams
Pounds vs. Ounces: 1 pound = 16 ounces
Inch vs. Centimeter: 1 inch = 2.540 cm
Inch vs. Millimeter: 1 inch = 25.40 mm
Gallons of Nitro to Pounds: 1 gallon of nitro = 9.5 pounds/1 quart = 2.37 pounds
Gallons of Alcohol to Pounds: 1 gallon of alcohol = 6.6 pounds/1 quart = 1.65 pounds
Gallons of Gasoline to Pounds: 1 gallon of gasoline = 6.2 pounds/1 quart = 1.55 pounds
Gallons of Water to Pounds: 1 gallon of water = 8.3 pounds/1 quart = 2.08 pounds
Gallons of Oil to Pounds: 1 gallon of oil = 7 pounds/1 quart = 1.75 pounds

Metric and Standard Conversions

Kilometers to Feet: 1 kilometer = 1,000 meters = 3,280.83 feet
Kilometers to Miles: 1 kilometer = 1,000 meters = .6215 mile
Meters to Inches: 1 meter = 100 centimeters = 39.37 inches
Meters to Yards: 1 meter = 100 centimeters = 1.09 yards
Decimeter to Inches: 1 decimeter = 3.937 inches
Centimeter to Inches: 1 centimeter = .3937 inches
Kilograms to Pounds: kilograms/2.20 = pounds
Pounds vs. Grams: 1 pound = 453.6 grams
Ounces vs. Grams: 1 ounce = 28.35 grams
Grams vs. Millgrams: 1 gram = 1,000 milligrams

Engine and Performance

Cubic Inches (CID) = CC ÷ 16.39
Cubic Centimeters (CC) = CID x 16.39
Lbs/hr. (LPH) = divide cc/min by 10.5
Gallons/hr. (GPH) = divide lbs/hr. by 6.0

Automotive Plumbing

-AN Size to Fractional Equivalent

-3 AN = 3/16″
-4 AN = 1/4″
-6 AN = 3/8″
-8 AN = 1/2″
-10 AN = 5/8″
-12 AN = 3/4″
-16 AN = 1″
-20 AN = 1-1/4″
-24 AN = 1-1/2″

Cheat sheets have a bad connotation attached to them. They were definitely frowned upon in school and not always accepted in the workplace. With so many equations and formulas to remember in the auto shop having thes eon hand can be a bi time saver. Copy it to your phone, print it if you feel old school or just bookmark it on that CFT screen shop computer that runs AOL dial up.

Racing Carburetor CFM

Racing Carburetor CFM = RPM x Displacement ÷ 3456 x 1.1
Note: Summit Racing also offers this CFM Calculator to make the job easier.

Displacement

Displacement = .7854 x Bore2 x Stroke x Number of Cylinders

Correct Compression Ratio (CCR)

CCR = FCR (Altitude/1,000) x .2
Note: You can also take this Compression Ratio Calculator tool for a spin.

Tire Diameter

Tire Diameter = (MPH x Gear Ratio x 336) ÷ RPM

Rocker Arm Ratio and Valve Lift

Gross Valve Lift = Camshaft Lobe Lift x Rocker Arm Ratio

Horsepower

Horsepower = (RPM x Torque) ÷ 5,252

Torque

Torque = (5,252 x HP) ÷ RPM

Rod Ratio

Rod Ratio = Rod Length ÷ Crank Stroke Length

Average Piston Speed

Average Piston Speed = Crank Stroke x RPM ÷ 6

Rear Gear Ratio

Rear Gear Ratio = (RPM at Finish Line x Tire Diameter) ÷ (MPH x 336)
Note: You can also save this link to a handy Gear Ratio calculator.

Volume (CCs) of Deck Clearance

CCs of Deck Clearance = Bore x Bore x 12.87 x Depth of Deck Clearance

Volume (CCs) of Head Gasket

CCs of Head Gasket = Bore x Bore x 12.87 x Thickness of Head Gasket

Compression Ratio

Combined Chamber CCs + Gasket CCs + Deck CI CCs + (Displacement x (N))

÷

Combine Chamber CCs + Gasket CCs + Deck CI CCs

(N) = 2.0483 for  8-cylinder. (N) = 2.7311 for 6-cylinder. (N)=4.0967 for 4-cylinder.

These formula are sponsored by Summit Racing.

William Connor

As the Editor, William is responsible for all the good, the bad, the ugly and the indifferent that happens at 4WAAM. William brings a wide range of experience to this role having been a cook, a painter, a machinist, part time mechanic, computer programmer, and writer. He also wields a freely shared opinion on just about everything., just ask him.

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