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aseem aseem is offline
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Join Date: Jan 2002
Location: Oslo, Norway
Posts: 559
Garage
Timing belt replacement incident

Hi guys. I have been working on replacing the timing belt on my 1989 GT, rebuilding the belt tensioner and replacing the coolant pump at the same time. Also some serious cleaning.

Everything has moved smoothly, until it was time to put the new belt in. The engine is positioned at 45 degrees before TDC, and the fly wheel lock is in place. I was threading the belt according to the WSM, and was checking the tightness between the oil pump and driver side cam wheel when the belt suddenly slipped. I thought the teeth slipped, but I soon found out that the cam shaft had jumped forward.

The driver side cam rotated clockwise seen from the front past the TDC mark on the wheel.
This picture describes the situation:

Black arrow is the timing mark on the back plate. The blue arrow is the TDC mark on the cam wheel, and the red arrow is my 45 degree before TDC mark.



I can't easily move the cam back to my 45 degree mark. I have read that at 45 degree before TDC, the cams should be able to move without damaging the valves. But this sentence from the WSM scares me: "Damage may be caused to the valves if the camshafts move suddenly".

So, what kind of situation am I in here, and what can be done to get out of it.

Appreciate any input on the subject.
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Arnljot
1980 930 GT35R, TurboKraft IC, 965 P&C, 964 Cams, Tial WG, ported heads, BLWUR, RarlyL8 hdrs&mfflr, Zeitronix logger & wideband
1989 928GT
1972 BMW 3.0S

Last edited by aseem; 02-16-2020 at 11:39 AM..
Old 02-16-2020, 10:41 AM
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