MED CAM­BELT CON­VER­SION

MED has launched a new, ver­sa­tile cam­belt con­ver­sion kit for the A-Se­ries en­gine. We demon­strate how it’s in­stalled...

Mini Magazine - - Contents -

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...

Words and Pho­tog­ra­phy Stephen Col­bran

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

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