How to keep cams in position after removing sprockets?

kfet

I have read through the available guides including the pdf from total vauxhall and I can see no mentioning of keeping the cam shafts in position once the sprockets are removed. From what I understand the valve springs could cause the cam shaft to rotate, potentially making valves and pistons touch... Are the cams actually locked or will they stay put provided the engine is kept at TDC for cyl. 4?

The way I understand the cam locking tool described in the mentioned pdf it is merely to keep the sprockets locked so that the bolts can be undone, right? and so when the sprockets are removed there is nothing locking the camshafts in position? But then again, the photos in the pdf guide shows two guys labouring to loosen the cam sprocket bolts, one holding a spanner at the cam side while the other attacks the sprocket bolts. I would have thought that with the proper cam shaft locking tool there would be no need for the other guy holding the spanner? Or i might be confused... Would anyone be able to clear up things for me?

My 05 Zafira is running fine with little to no cam noise (my mechanic believes the slight sound to be a tappet rather than the chain.... I don't know) But the car has done 132000kms with only the scheduled oil changes. I saw in some post here that the chains should be replaced at 100000miles, which with my amount of driving would be a couple of years down the track... I feel pretty sure that I wanna go ahead with the timing chain and balancer chain replacement but it might be overkill? Mechanic seems to think so. Any suggestions? Just leave it till there's definite rattling from the chain? I will change the oil every 7500kms from now. Might be enough to keep things at bay... I'll be kicking myself if the chain snaps though! How often does it actually happen without warning? Are those people just ignorant to engine sounds?

Regarding the cam locking tools I've seen some nylon ones on ebay: http://cgi.ebay.co.uk/TWIN-CAM-LOCKING- ... 230215c448

Do these things work? I assume I'd need two, one for each cam?

Thanks for any help!

Kristian

JohnnyN

Criss cross 2 spanners over the cams. Then use a set of mole grips to hold the 2 spanners together.

We had to use grips on mine as I don't have standard cams.

kfet

Thanks Johnny! simple and clever!

But the GM special tool would only hold the sprockets for undoing the bolts? Still confused as to why that total vauxhall article needs two guys to undo the cam sprocket bolts, given that they even have the GM cam locking tool...? Is there a risk of breaking stuff if only locking the sprockets and applying force to the bolt (without holding the camshaft with a spanner)?

Thanks

VXed

They don't move. Plus if they do they would not put pressure on the valves as the valve springs would be pushing the cams off the valves. They don't move anyway, as at TDC there is little or no pressure on the cams from the Valve springs cheers..

solorider

in the haynes manual they use cable ties to hold the chain to the cam wheels

vocky

solorider said:
in the haynes manual they use cable ties to hold the chain to the cam wheels

thats what I use too :thumbup:

benny

i dont hold themlet them losse and roam free no reason to hold em ..... use the 24mm spanner to turn them and place / line the sprockets up i dont even cable tie anything let it all hang out so to speak lol the cams or crank aint gonna move very far from home ....... cryb..

cavaddict

Hmmmm

cavaddict

kfet said:
Thanks Johnny! simple and clever!

Heh heh heh 😃