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determine flywheel weight

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mechanic6

Automotive
Dec 10, 2007
23
was discussing with a friend who is starting to build a kitcar.
the car is configured for ford engines.
he is thinking of using a ford crate engine.
new 302 engine built to 340 hp @6500.
the finished car will weigh 2700 to 2800 lbs.
question:the ford built engine does not come supplied with a flywheel.
how would you determine what weight of wheel to use?
the car will be driven on the street.
(i favor a heavier wheel myself)

M6
 
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When it comes to drivability vs acceleration, the flywheel is certainly one of the tunable items. When doing calculations, be sure to include reasonable estimates of the driveline rotating intertia, as well as the crank, rods, & pistons; and keep in mind that the % contribution of the rotating/reciprocating inertia ahead of the transmission vs behind the transmission varies depending on which gear you're in.
I don't know of a rule of thumb for selecting the flywheel "weight" (should really be "I", moment of inertia), but you definitely can get away with lighter than stock for the application. It's just a trade-off between drivability and acceleration. The trade-off for both is most pronounced in first gear, of course.
 
More important for Ford small blocks is to get a flywheel with the correct balnce weight. Ford used 2 different balance weights on the balncer and flywheel over the years, 28 ounce and 50 ounce. If you don't have the correct one for both the balancer and flywheel, the engine will shake itself apart. Your engine builder should be able to tell you which you need.
 
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