play in cam chain?

[Toby_Unna]

decided to do the valve clearances on my m30b35 powered e30 today, it's tapping a little from the top.

so i have the car in 5th gear and am rolling it along by hand to move the cam around to do each clearance.

i noticed that when the car is rocked back and forth, the play between cam chain and cam sprocket seems large - i.e. if you hold the car backwards against the reisstance of the engine, then pull it forward, the cam chain moves round a little before it starts turning the cam, maybe up to 2mm at the sprocket teeth tips.

this seems wrong to me, surely the cam timing can't be very accurate with this much play?

conincidently - the motor has very weak top end power (above 4.5k rpm) compared to my identically-engined m535i, might this be the reason for the lack of power?

[Simon13]

or the tensioner is shagged

[MasterBates]

On these, the tesnioner is just a nylon slipper against the chain with a big spring. However, the top chain sprocket is prone to wear, more on the 4cyl M10 than the M30 but the M30 ones do wear. You'll find that every other tooth will be worn, i.e inner link, outer link, inner link, outer link etc etc. On the M10, fitting a new or good used top sprocket is easy enough but the chain will be horribly noisy afterwards unless you fit a good strong spring - the oil pressure relief valve spring from a BL A Series engine (i.e a Mini or something) makes a good job of silecing it. These are easy to find; just below no.4 (rear) plug you'll see the steel oil return pipe going down to the oil filter housing. Look just below the top union bolt for this pipe and you'll see another big bolt, about 24mm. Remove this and the bolt and spring will pop out. All the usual BL crap has this, Metro, Ital, Mini etc.
If push comes to shove, replacing the chain isn't a disaster. I don't know if you can still buy split link chains but you need the one with the clip as opposed to the link that needs rivetting. To be honest, when I did an M10 chain on a 518i, I just removed the front timing cover.
But, if the top sprocket doesn't look too worn, try the stronger spring. If the chain/sprocket are worn enough to cause a problem, you will hear quite a lot of noise.

[Toby_Unna]

cheers for that. the engine's really quiet (or it is now i did the one clearance that was miles out) so it it worth doing anything at all?

i'm not worried about how much noise it makes, just wondering if the cam timing is out a fraction and affecting the performance?