CLUTCHES: A clutch is made up of two major parts; the pressure plate and the clutch disc. Each has its own purpose. Clutch pressure plates come in two styles - 3 finger Borg & Beck or a multiple finger diaphragm type. When a hydraulic clutch system is going to be retained, it is critical that you use a pressure plate that is compatible with the existing hydraulic system. The pressure plates that we offer are the diaphragm type and are available for both the mechanical and hydraulic clutch linkages.
There are several engine conversions that will require a mixed combination of pressure plate and disc components. Quite often we will use a Ford clutch disc with a Chevy pressure plate, or a Chevy clutch disc with a Ford pressure plate in order to make the proper clutch connection.
The pressure plate and disc must be aligned to the flywheel prior to securing the pressure plate bolts. Special tools are made for this alignment, or the transmission input shaft can also be used. The pressure plate bolts should be tightened progressively to the flywheel, and you must use the recommended torque specifications provided by the manufacturer. When assembling the clutch & pressure plate to the flywheel, it is also crucial that you check the clutch disc spring clearances on the flywheel-to-crank bolt heads. Many times, if a flywheel has been resurfaced, this can be a problem.
FLYWHEELS: The flywheel is one of the most important parts of your engine conversion. Special care should be given in selecting the proper one. Flywheels are available in many sizes, tooth counts, and materials. Most factory 4WD vehicles, such as Jeeps and Toyota Land Cruisers, are furnished with a heavy cast iron design. The weight is a very important factor when serious offroad driving is planned. It seems that the weight has a tendency to keep the engine’s performance at a low RPM - ideal when in the rocks and rough terrain. For a vehicle that is used very little in offroad use, a lighter flywheel will be sufficient. In either case, make sure that the flywheel has been balanced and has a good surface for clutch contact. When installing a flywheel onto the engine crank, make sure you use the special flywheel bolts and factory torque specifications. On Chevy and Buick manual transmission conversions, we have standardized our bellhousing lengths for flywheels that are 1" thick. If you are going to use a flywheel that is either thinner or thicker, then modifications may be required. These modifications can be as easy as using an adjustable ball pivot. Some applications may require additional surfacing from the face of the flywheel.
Chevy V6 & V8 engines can be equipped with either a 153 or 168 tooth flywheel. You must make sure that engines 1986 & newer have the proper balancing since these engines are all externally balanced. The 1985 & earlier blocks are internally balanced. The flywheels between these years cannot be interchanged. In the late 90’s the Vortec Gen 3 engines came out and these engine used a few different flywheels. These flywheels are not interchangeable with anything earlier and can cause some problems when converting to an earlier transmission. For these blocks refer to our P/N 712500M and 712500A for flywheel and flexplate options
On Buick engine conversions, there are three styles of flywheels available. Our adapters are designed for use with only the flat-type style of flywheel. The recessed and raised surfaced flywheels may have some difficulty with relation to clutch performance. Manual flywheels for Buicks are sometimes hard to find since most of these blocks were originally connected to an automatic transmission. Centerforce offers a 160 tooth, 35 lbs. Buick V6 flywheel, AA P/N CF700010. The 225 out of a CJ has a recessed flywheel and is a odd fire block, 231’s out of GM cars up to 1977 are normally odd fire blocks also. 1978 and later 231’s were normally coupled to an automatic and they were even fire V6’s. You can use our flywheel on a odd fire block but the flywheel must be rebalanced for the odd fire block.
The Ford flywheels are available in two different tooth counts - 157 & 164 tooth. Since the starter bolts and indexes to the Ford bellhousing, it is crucial that the flywheel is matched to the bellhousing. Some of the later model Ford blocks only offered one diameter or tooth count flywheel. However, our adapter may require the opposite. On these applications, you will need to have the correct flywheel diameter balanced to the year of the block. Ford blocks are 1968-80 28oz. balance and 1982-97 50oz. bal.
Before installation of your flywheel, be sure to clean all surfaces that contact the pressure plate and disc so that there is no oil or grease contact. If a flywheel has been resurfaced, you should make sure that the bolt hole depth that holds the pressure plate to the flywheel has sufficient clearance for the bolts. There have been occasions when the depth does not permit the bolt to secure the pressure plate, causing severe clutch problems.