It is strongly recommended you read the following discussion on how flywheels and clutches actually affect the way the car feels and reacts to driver input. Please be sure you are ordering the type of flywheel, pressure plate, and disc combo that applies to your needs and driving style.
Flywheels and Clutches
FLYWHEELS: The actual horsepower of the engine does not change related to the weight of the flywheel. However, to increase the engine RPM, and accelerate the car, all rotating weight (as well as the entire car) must be speeded up. This requires power, and the heavier the part, the more power needed to speed it up. The less power needed to speed up the flywheel (and rotors, clutch, driveshaft, wheels, tires, car, etc.) the more power available to speed up everything else. The question we are asked frequently – “How much more horsepower will my engine have with a light flywheel” – is not the right question, because the answer is NONE. What you will have is more available horsepower to accelerate the car and yourself down the road.
The trade-offs are as follows: the heavier the flywheel, the smoother the idle, the easier the starting is from a stop, and the smoother the cruising/slight throttle changes are. BUT – the slower the acceleration is. The lighter the flywheel is, the harder it is to get the car moving from a stop (just requires a somewhat higher RPM before the clutch is let out – which wears the clutch faster), depending on porting, intake, and exhaust, the idle will be somewhat rougher, and some “jerkiness” may be noticed while cruising. BUT – you will be able to accelerate faster. This is true to a much lesser degree on fuel injected engines than on carbureted engines.
The above reasons are why there are basically three types of flywheels offered. The stock units are fine for most “normal” driving, as done by the vast majority of drivers. The light steel ones are great for “spirited” street driving, middle range autocross classes, some drag racing (heavier is sometimes better), and just general high-performance applications that will still be driven on the street sometimes. The lighter aluminum flywheels are recommended for all road race applications and fuel injected street driven cars where the highest performance is desired.
NOTE: Excluding the TURBO, all the different flywheels and clutches, from 74 through 92, are basically divided by 215mm clutch (74-82), and 225mm (83-92), then by rear counterweight needed for the engine. We mix and match these all the time. This means if you want to put the larger diameter clutch assembly on a pre-83 application, just let us know – it is no problem. You just need to remember what diameter you have when you next purchase clutch parts.
CLUTCH PRESSURE PLATES: (Clutch Covers) are available in three types (excluding the Centerforce design), STOCK, STREET/STRIP, and RACE. The stock units work fine for normal, and reasonably hard driving. The STREET/STRIP units have more clamping pressure for less chance of slippage when driven hard, with only a slight increase in pedal pressure. These are the normal upgrade for anyone wanting more than stock clamping pressure. The RACE units give much more clamping pressure, and a “fairly” noticeable increase in pedal pressure. These are great for racing, and usable for the street, if you don’t mind the harder pedal, and you do not have to do any stop and go driving. All three types are built from new parts, therefore there is no core required.
CLUTCH DISCS: These are what most affect the “feel” of the clutch engagement. The range and “feel” of pedal travel between disengaged, and fully engaged, is determined by the cushioning spring between the sides of the fiber disc (or lack of), and by the sprung center piece (or lack of) between the outer engagement material, and the spline center going to the transmission. The cushioning spring between the engagement sides increases the range of pedal travel between “starting” to engage, and fully engaged. This is due to the pressure plate having to compress the spring to fully clamp on the disc. The discs without this spring are a very much more “abrupt” grab, which makes them harder to drive smoothly on the street.
Discs with the fiber lining wear at normal rates, under normal driving conditions, but disintegrate if overheated, and/or driven REAL hard and abused.
The metal fiber “puck” type discs, for the most part, wear the flywheel and pressure plate faster than the disc. They will take much more heat and punishment before failure, but do not like to be “slipped” very much (burns up the flywheel/pressure plate first).
The discs with the sprung center section do not transmit as much shock loading to the drivetrain, so they are much easier on transmissions and rear ends. They also give you an increase in the time between “just about engaged but not moving much yet” and fully engaged (or “oh sh__, I stalled it again).
(Generic Image – # of springs changes)
|Sprung center, cushioning spring – Best for all-around street driving, and some “spirited” fast driving.|
|STREET/STRIP HEAVY DUTY|
|Sprung center, no cushioning spring, fiber lining – Good for hard street driving, autocrossing, marginal for drag racing due to lining disintegration from overheating when leaving the line, fairly abrupt pedal engagement.|
|Sprung center, metal pucks with no cushioning – Best for very hard driving, drag racing, serious autocrossing, good for road racing where weight isn’t all important but transmission life is, abrupt pedal engagement.|
|Solid center, metal pucks with no cushioning – Serious racing, very abrupt engagement, lightest weight, best for road racing where there are no standing starts, also drag racing but flywheel and pressure plate life is short.|