Classic Austin Mini Duplex Timing Chain And Gearset Kit

Classic Austin Mini Duplex Timing Chain And Gearset Kit

Classic Austin Mini Duplex Timing Chain And Gearset Kit
Qty:
$65.95
Part No: C-AJJ3323
In Stock
Internet Price $65.95
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Budget standard cast duplex gear and chain set, road use only. Comes with both gears, a new chain and two countersunk screws to replace the front cover bolts.
(AEA687 new counter-sunk screws are included in this kit)
General: Camshaft Drive Systems: If you are working on your engine and you want to do it right then you should consider how you are going to drive the camshaft. People often spend a lot of time picking the camshaft and then ignore the exact reason they spent so much time picking the cam. Driving the cam and controlling the timing relationships between the cam and the crank is what camshaft drive systems are all about. It makes no difference what the cam does if it does not do it in sync with the crank and pistons. The stock system on many 848, 948, 998 and 1098cc engines is a single chain drive between the crank and cam. The 'S' and some 1275 have a much better "duplex" chain. But even those do wear out! The best judge is to check it while you are taking it apart. With the timing cover off the engine rotate the crank a slight amount back and forth. The camshaft must move the exact distance at the same instant! The least expensive but better than an old one is a stock cast gear and chain set, This budget standard cast duplex gear and chain set is the next step up, for road use only. 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! Fits a Sprite , MG Midget , Mini , and Morris Minor.

The front place will have to be countersunk as shown "X" to take the screws CMZ407, which will replace the existing hexagon headed screws, which would foul on the timing chain. Check for clearance on chain all round and align gears as per workshop manual.

When using "A" plus timing covers, there is a small round pressing at the bottom which needs making flat to allow timing chain clearance.

Ensure that the timing chin oil thrower 12A1148 is correctly fitted with the letter "F" facing you, or on early engines, the lip facing outwards.




Duplex Cam Drive - Cam timing information

IMPORTANT NOTE.
Minispares duplex kits are genuine AE Hepolite products now owned by Federal Mogul who were the original engine components supplier for Mini. It is however very, very rare that simply fitting these cam drive gears will give the correct cam timing for any particular camshaft installed. Although it will likely to be very close on factory-ground OE camshafts, or from new blanks it is unlikely to be the case on re-profiled camshafts. The main reason for this is when the cam re-profiler needs to make sure the new profile and LCA (lobe centre angle- angle between lobe centres of inlet and exhaust lobes) will fit the core cam being used it may be necessary to re-align the cam lobes in relation to the cam gear key. Because of this it is highly recommended that the cam timing be checked/ re-set to the cam manufacturer or cam suppliers specifications to maximize performance potential.

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