02/12/11 - Shock absorbers would better be thought of as spring dampers, because their function is to control the rate at which suspension springs compress and rebound. A shock uses hydraulic resistance,created by passing oil thru ports and valves, to dampen the movement of a vehicle chassis. Shocks control two types of movement; rebound and compression.
Rebound
Rebound (extension) is the shock's resistance to being pulled apart. It can be used to control chassis separation, the point at which the axle housing is pushed away from the chassis and the tires are applied to the track. A shock with a high (stiff) rebound number holds the chassis and axle together to prevent excessive separation. Excessive separation can lead to undesirable effects like wheel hop or tire shake, which can occur as the tire tries to return to its original form. Rebound is used to plant the horsepower you create to the ground.
Compression
Compression (bump) is the shock's resistance to the chassis moving down or the axle housings moving up or into the chassis. The compression adjustment is an important setting, as it determines how long the tires are held down on the track after chassis separation. Compression dampens the suspensions tendency to unload the torque and weight transfer created by rebound.
Reading Shock Ratios
The first digit in a shock ratio is Rebound, the second is Compression. Therefore, a shock marked 90/10 has been set at 90 for rebound and 10 for compression.
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02/12/11 - What Body Type is My GM Vehicle?
- A-Body: 1964-1981 Chevelle, Malibu, El Camino, Concourse wagon, Monte Carlo, and Monte Carlo SS; Buick Special, Regal, Century and Grand Sport; Pontiac Lemans, Grand Am; Oldsmobile Cutlass, 442, Vista Cruiser Wagon
- F-Body: 1967-2002 Camaro and Firebird
- G-Body: 1968-1972 Grand Prix; 1982-1988 Malibu, Malibu Wagon, Monte Carlo, Monte Carlo SS & LS, Regal, Grand National, Bonneville, Grand Prix, Cutlass
- X-Body: 198-1979 Nova, Omega, Apollo and Ventura
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02/11/11 - Calculating Fuel Requirement...It's Just Simple Math!
Determining how much fuel your fuel pump needs to be able to provide is no mystery. It comes down to mathematics. The engine in your car takes in air and fuel and converts them to horsepower. To make this horsepower, your engine will consume a certain amount of fuel referred to as the "Brake Specific Fuel Consumption", or BSFC. The BSFC is generally estimated to be 0.50 for most naturally-aspirated (non-turbo/super-charged) engines.
So do the math: Horsepower x .50 = Fuel needed per hour in pounds (pph-pounds per hour). Gasoline is calculated at 7lb per gallon
Example - Engine that produces 400HP @ 6000 RPM:
400 x .50 = 200 lbs equal 29 gallons at 6000 RPM
However the calculation does not end there. Factors such as engine RPMs, the diameter of fuel line and other plumbing restrictions, the g-forces upon launch, line pulse created by pressure regulators and other factors affect pressure output. Therefore you must factor in a safety margin. Most professionals recommend a safety margin of 30%.
Remember, a properly regulated fuel system will not sufer from too much fuel, but fuel starvation can be disastrous.
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02/11/11 - HOLLEY
Vacuum secondary or mechanical secondary carburetor?
How do I know if I need a mechanical or vacuum secondary carburetor?
As a rule of thumb, vacuum secondary carburetors work best on the following:
- Relatively heavy vehicles
- Street gearing
- Automatic transmission
- Engines built more for low-end torque
Conversely, mechanical secondary carburetors seem to work best on:
- Relatively light vehicles
- Strip gearing (4.1 or numerically higher)
- Manual transmission
- Engines built more for top-end horsepower
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