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Dowel type exact timing adjustable toothed belt cam drive system.
This comes as a complete kit to convert from chain drive.
The adjustment is by interelating holes between the cam boss and cam gear. Located by a dowel. The holes give 2 degree increments of adjustment. Combined with a 1 degree offset key it facilitates EXACT timing of the camshaft. Fits all A Series engines and includes a breather pipe take off.
General: Fitment of an uprated cam drive system is essential when building a performance engine. Timing scatter induced by the standard set up can reach up to 15 degrees once the single row chain has stretched, which it does after only a few miles. This scatter not only affects the cam timing, but also the ignition, the distributor being driven by the camshaft. Power loss suffered by this phenomenon is substantial. Replacing the standard single row (simplex) system with a dual row (duplex) system greatly reduces the problem; use of a toothed belt system all but eliminates it. The belt system vastly reduces valve train noise and also helps damp out some of the odd harmonics generated by the 3 main bearing 'A' series engine. It is also extremely important to time any cam in to its required setting to obtain maximum performance, especially with performance cams. The 'dot to dot' method can, because of manufacturing tolerances, be out by as much as 15 degrees. Anything above 2 degrees out and power suffers -- most noticeably in small bore engines. In race engines you probably lose 1 hp for every degree the cam is out, more when over 6 degrees!
Adjustable belt drive timing kit, C-AJJ3328
Additional Related Articles:
The ubiquitous toothed belt cam drive system, originally developed for use on high performance race engines, is now generally accepted as the norm on all state of the art, modern engines. The application of this drive system gives very accurate ignition tming and quiet running, advantages that do not diminsh with time. The fibre glass reinforcing in the belt all but eliminates the stretch suffered - usually excessively - by chain driven systems. The retention of accurate ignition timing keeps performance at a peak, rather than deterioration suffered with the scatter induced by chain drives. The MINI SPARES KIT enables the 'A' Series owner to benefit from such technology.
The adjustable cam gear allows up to 9° of adjustment, facilitating accurate cam timing, particularly when installing a performance camshaft.
FITMENT: After removing the old cover and gears, remove keys and clean cam and crank surfaces, ensuring new gears are a light slide fit. Remove cam plate retaining bolts and fit without shake proof washers, using thread-loc instead. This is to eliminate binding between the cam centre boss and nut heads when non original bolts and washers are used. Refit keys, once again checking that the gears are a light slide fit. If this is not done, the alloy seal-cover will be damaged when gears are removed using the cover as a lever point. Also if the crank key is too proud, it will form a ridge in the bottom pulley when forced on. Consequently this will cause an oil leak.
After checking that the gears are a lgiht slide fit, press the seals squarely into the seal-cover. With the gasket supplied in place, offer the cover up to the engine. Before screwing in retaining bolts tightly, fit the two gears through the seals and onto their relevant shafts - this will centralise the cover, helping to avoid oil leaks. Tighten the bolts down evenly to ensure the cover is pulled down square. DO NOT OVER TIGHTEN.
The cam gear can be set in the standard position by aligning the two dots adjacent to each other on the cam gear centre piece and outer section, then inserting the peg through the holes next to the dots.
Adjustment is achieved by removing the peg with the screw supplied, turning the outer section in the required direction to advance/retard the timing, then re-inserting the peg in the required holes once lined up. Each hole is 1° offset, so gives 2° of crank timing. A 1° cam key will allow even greater adjustment.
Once the cam timing has been set and the peg is in place, fit the lock tab/peg retaining plate, then the cam nut and tighten enough to pinch the cam wheel assembly so that the end float can be checked. This should be 0.003"-0.007".
The pulley should be torqued up to 61 lb ft. Bend the locktab up, but NOT a section covering the locating dowel. Make sure the crank pulley guide plate is fitted before refitting the damper pulley.
NOTE: The kit comes with a breather pipe, if not required, blank it off.
The cover is split to facilitate inspection of the belt. Regular inspection should be carried out on installations used in hostile or severe conditions. The belt should be replaced every 20,000 miles in normal road applications. The kit has been used on racing engines up to 9.500rpm.
Take care not to damage the belt when assembling, as this will obviously cause failure.