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cam belt replacement

hi guys, help required ??. i have just replaced the head gasket/water pump ect on my 156 the prob i have is when fitting new cam belt i have the cam locking tools in place so i now cylinder one is at tdc , the cam belt has 3 white marks on it which need to be aligned with the cam shaft and the 2 top cam pulleys but when cam shaft is rotated through 2 comp revolutions the marks on the belt no longer align with the cam pulley marks ?? untill a few more revolutions are completed then they come back into alignment , then go off again and so forth anyone know why this is and is it normal ???
many thnx guys
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Re: cam belt replacement

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Originally Posted by iceman288 View Post
hi guys, help required ??. i have just replaced the head gasket/water pump ect on my 156 the prob i have is when fitting new cam belt i have the cam locking tools in place so i now cylinder one is at tdc , the cam belt has 3 white marks on it which need to be aligned with the cam shaft and the 2 top cam pulleys but when cam (DO YOU MEAN CRANK???) shaft is rotated through 2 comp revolutions the marks on the belt no longer align with the cam pulley marks ?? untill a few more revolutions are completed then they come back into alignment , then go off again and so forth anyone know why this is and is it normal ???
many thnx guys
Provided they all line up again eventually all is well. A double check is to see if they "miss" by the same number of teeth.

It's because the belt is not exactly (say) two engine revolutions long, it's (say) one and a half so the same bit of belt has moved on in two revs, but comes home eventually.

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Re: cam belt replacement

Mark the crank and camshafts, rotate the crank through 360 degrees and all the marks shoud be back where they started. If they are not then you have probably bent the valves trying!

Paul.
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Re: cam belt replacement

thnx for the advice paul, i hope i aint bent the valves , don't see how i could have as i bought the cam lobe locking tools to get everything in the correct pos before turning it over ? the alfa shop in norwich advised me to use the tools as it was the only way of assuring i would not cuase any damage when setting up ??. so are you saying m8 that every revolution should keep the belt marks aligned with the crank and cam marks ?? , many thnx for your help m8.....
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Re: cam belt replacement

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Mark the crank and camshafts, rotate the crank through 360 degrees and all the marks shoud be back where they started. If they are not then you have probably bent the valves trying!

Paul.
ERRRRR! I hate to disagree with a RegRep but that aint so.

For 1/

If you rotate the crank 360 deg then the cams will only turn 180 deg leaving the marks nowhere near the belt itself!

For 2/

Rotating the crank another 360 deg will bring all the marks alongside a piece of belt, BUT NOT WHERE THE BELT MARKS ARE unless the belt is exactly twice the length of the distance round crank pulley, which it ain't!! D'ya see what I mean?

Lets say there are 36 teeth on the crank pulley and 72 on each cam (the actual numbers are irrelevent as it is all a question of percentages) then one turn of the crank moves the belt 36 teeth and two turns moves it 72 teeth. Not far enough to bring the white marks into play

On this scale the belt is gonna be 216 teeth or another multiple of 72 or else the marks would only line up very rarely.

If there were timing marks like on the old "Nord" or "Sud" engines, ie on the engine block/head and on the pullies, then yes you would be right but when the marks are "on the belt" as described by iceman then things are different.

Cheer up Iceman you are OK!

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