Cam belt tension/timing

[Zaphod]

Having what might be a spot of bother or nothing at all..
fitting the cam belt with the crank at TDC, and the two dots lined up on a straight edge between cam centres, however when it come to set the tension the crank moves, best I seem to be able to manage the crank moves to approx 2.5 ATDC, when rotated two full revolutions to TDC the cam pulley dots are about half a tooth off lining up, while this is the first 900 I have tried ti fit the belt to it is not the first cam belt by a long way, however I am being much more fussy with this one! (I even acquired a Burroughs guage..)

[Tanz]

I fitted a new cam belt yesterday. The first time I tried the crank moved so I had to try again. I got the belt on the crank and then went anticlockwise so exhaust cam pully then inlet then auxiliary. Although the 2 dots on the cams looked lined up, when I tried to get the belt on the cams with reasonable tension between the crank and exhaust pulley, the teeth were half a tooth out and the belt wouldn't fit in the 'teeth' of the cams without making the belt slack. I tweaked the cams slightly so the belt would fit snugly on the cams and the dots still looked in line. Even using a steel ruler it is still difficult to be absolutely sure the dots are in line - obviously mine were half a tooth out. Then put the belt on the auxiliary pulley and tensioned it up. You can be slightly out on the auxiliary pulley as any error can be dialled out with the distributor. Hope this helps - makes any sense.

[AndyC]

It doesn't really matter, as long as it's up to hajf a tooth out. If it's more , then adjust it to the next tooth. There's no adjustment to this , unless you have adjustable cam sprockets. It can be made worse if a head is skimmed as it shortens the distance between the crank sprocket and head sprocket.