MED CAMBELT CONVERSION
MED has launched a new, versatile cambelt conversion kit for the A-Series engine. We demonstrate how it’s installed...
We show you how to install a cambelt conversion, using MED’s new, versatile cambelt conversion kit.
When it comes to the variety of camshaft timing setups, we’re fortunate with the Mini’s A-Series engine. From the standard simplex chain to superlightweight adjustable race designs and gear drives, choosing a suitable method to link the camshaft and crankshaft comes down to two factors - application and budget.
The first upgrade to the cam timing would be a high quality chain like the German Iwis types; an investment that will save money in the long-term as they are far less prone to stretching than budget types. A stretched chain will do performance no favours, with inaccurate cam timing meaning the valves open and close at the wrong moment. From there is the additional strength/longevity offered by a duplex twin-row chain setup, at the cost of extra mass and resistance.
Ideally when upgrading the camshaft, it’s far easier to achieve accurate cam timing with an adjustable vernier type setup than offset keys and a non-adjustable cam sprocket. Race engines utilise the lightest possible simplex designs with aluminium cam and crankshaft sprockets, all in an effort to reduce mass in the rotating assembly and increase engine responsiveness/acceleration. For higher mileage road use, this is far less of an issue, so adjustable duplex designs with steel sprockets will give the best longevity.
From there you have a conversion to a rubber cambelt, as with a large majority of modern production cars. These setups are more than capable of regular road use whilst also proving popular with full-race engine builders. The belt is far lighter than a chain, while also helping to effectively dampen out any damaging harmonics from the valve train. A split cover design allows far easier cam timing adjustment in situ, if experimenting perhaps on a rolling road/dyno. So if you’re looking for the ultimate cam timing setup for the A-Series then the cam belt conversion has to be up there.
How about the disadvantages? With a separate housing required, the extra material and machining time increases cost. There’s also a shorter service life on a belt to a decent quality chain, so regular replacement is highly recommended.
The newest cam conversion to be launched is an updated version from MED’s previous HTD design. Although the HTD belt was more robust in theory, sourcing replacements in this very short length has become both difficult and expensive. The previous design also did not suit inline A-Series engines in Sprites and Midgets, so it is now a more versatile offering. Other tweaks include a change in the oil seal designs, which now sees a Mini primary gear seal for the cam vernier and a readily available seal for the crankshaft. Future service life then is very good, with replacement belts readily available. Here’s how the kit is installed...
COST MED Cambelt conversion - £350 Spare seal kit - £10 Replacement timing belt - £45 CONTACT www.med-engineering.co.uk 01455 618464 DIFFICULTY
Likewise, check the fitment of the camshaft vernier pulley on the end of the cam. We’re just using an old cam for example here - use soft jaws in a vice with a new cam. 3
6 If you’d prefer to fit a new timing plate to match the new cam belt kit, MED also produces a CNC-machined aluminium version.
1 The kit could potentially be fitted to an engine in situ, but it’s far less awkward away from the car. Better still would be to assemble as part of an engine rebuild. It’s recommended to first check the fit of the pulley on the crankshaft. Here’s the crankshaft pulley checked for fitment.
5 Place a new timing plate gasket on the block. The new belt drive conversion still requires use of the standard timing plate below.
2 If the pulley seems too tight, it’s easier to rectify issues now than when assembled in the aluminium casing. If the pulley is too tight, remove the woodruff key and check for burrs. Try to push the pulley back on and you’ll soon tell if it’s a burr on the key or the crankshaft tail itself. Ours went straight on.
If there’s a problem with fitment on the crankshaft or camshaft, you may either need to polish the end of the shaft or gently remove any burrs with a file. 4
13 Next install the camshaft pulley. This adjustable vernier is machined from 7075 aluminium for strength and light weight.
The plate fixes in place with countersunk screws at the crankshaft end... 8
7 This saves a minute amount of weight, but the main purpose is to upgrade the fixings with pressed-in studs. This takes away the common issue of stripping the threads in the plate.
...and slimline button head screws for belt drive clearance at the camshaft end. 9
Timing plate in place, fit a new timing cover gasket. Using both the cam belt conversion and aluminium timing plate will stop any leaks in this area. 10
12 First slide the crankshaft pulley in place, which should be straightforward if you’ve already checked fitment. The large diameter crankshaft pulley has belt-retaining rails to retain rigidity along the key way in this area.
Now place the outer casing of the kit in place, but don’t tighten the fixings just yet as you will need to centre the seals around the pulleys. 11
14 With the seals not centralised around the pulleys, tighten the fixings to the outer cam belt cover.
Now refit and tighten the camshaft retaining nut as with the standard setup. 19
The outer cover of the billet aluminium timing case is split diagonally to allow access to the camshaft vernier. This will allow cam timing adjustments in situ. 20
Refit the pulleys with the cambelt now in place. Following those steps ensures it will all line up correctly and seal the casing from engine oil. 18
The cambelt of choice is a high quality Japanese-made Gates item. MED recommends service intervals of one season on a race engine, or a conservative 15,000 miles to be safe on a road car. 17
15 Remove both pulleys once the fixings are tightened up. The large cap head screws require a 1/4-inch AF hex drive or Allen key.
If you recognise the orange seal - it’s a primary gear oil seal - so spares are very easy to find. 16
27 Note the orientation of the damper to the pulley as these are balanced together as a unit. Hand-tighten the cap head screws, or torque to 10lb ft if you have a suitably small torque wrench.
22 On a more complete engine you can now check and setup the camshaft timing as per the recommended specifications. Our dummy engine has no pistons, but here’s one we did earlier...
21 Install and lightly nip up the cover fixings to seal the cambelt assembly away from the elements.
The damper kit comes balanced and is supplied with an extra long EN24T steel bolt and washer. The standard bolts are comparatively very short on the thread. Torque the bolt to 70lb ft. 24
That’s the fitment complete. The crankshaft damper and pulley can now be installed. Here we’re using an MED extra large damper, which should prove more effective than the standard unit. 23
26 The plate is laser cut from stainless steel to fit straight over the pulley bolt.
For damper retention it’s recommended to do away with the standard lock tab washer and instead fit a proper lock plate. This also avoids the necessity for thread lock. First remove the four cap-head screws. 25