Factory Five Racing Mk3 Roadster, Assembly Manual

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Rear end gears
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Induction/Fuel Injection
There are three things an engine needs; air, fuel and spark. If you allow more of each of these into the
engine, it will make more power.
Throttle Body
Stock size: 58mm
A 65mm throttle body work well up to 350hp. Ford Motorsport sells a Cobra set-up that includes a 70mm
mass air meter, 24 lb. fuel injectors, and a Cobra computer (different fuel curves). This set-up is about
$400, which is very reasonable. It is good up to roughly 400hp.
Mass Air Meter
Stock size: 55mm
In order to increase the flow of air above 5000 rpm, upgrade from the stock mass air sensor. Aftermarket
70 mm or 75 mm mass air units are an excellent choice and have proven effective. If the mass air meter is
changed make sure it is calibrated for the injectors you are using or you will have to change the injectors
too. Pro-M or Ford Motorsport meters work the best. Usually the mass air meter is larger than the
throttle body.
Fuel Injectors
Stock size: 19lb/hr.
The stock injectors are good for exactly that, a stock engine. If upgrading parts, step up to 24 lb/hr
injectors. They are good up to about 400hp. Make sure that you have the mass air sensor calibrated to
the injectors you use.