Timing Belt Walk
#1
Drifting
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Timing Belt Walk
I'm having a problem with the timing belt. When we changed it last week, we tensioned it to the proper new belt tolerance of 2.7 +/- .03 and the problem as I see it is that the belt is not stretching as the engine heats up. I belive this because the belt continues to "walk" to the end of the cam sprocket. If I understand this correctly, and I'm asking for thoughts, verification. As the engine heats and expands, the belt should "stretch" some thereby maintaining a correct radius, for lack of a better term. If the belt is NOT streching, then it would make sense that it would "walk" as the engine heats and expands, the belt, in a effort to maintain its "radius" would tend to move toward the front of the cam sprocket. Am I correct, or nuts?
#2
Three Wheelin'
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Kevin,
Are you assuming the the camshaft sprocket or cranshaft gear is tapered so that the tight belt moves away from the engine? Interesting idea.
Is this causing a problem?
How did you figure this out? Did you go back in to check the tension after a week?
Are you assuming the the camshaft sprocket or cranshaft gear is tapered so that the tight belt moves away from the engine? Interesting idea.
Is this causing a problem?
How did you figure this out? Did you go back in to check the tension after a week?
#3
Drifting
Thread Starter
Have not checked tension, as I drive about 24 miles per day. I'm just a little bit compulsive about the timing belt. So I checked the inspection hole by the dist. and saw that the belt had moved.
#5
Drifting
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Still doing it The clutch feels great, though I'm sure that the leaking heater control valve is shortening its life a bit, but I'll be fixiing that soon enough.
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#10
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Wierd, it seems like guys usually talk about the belt moving towards the rear of the motor and get close to the rear belt cover, not vise-versa. Is the triple square bolt on your cam housing tight so there is absolutely no wobble to the cam sprocket? Next question is, is the belt 100% rubber, or is there some sort of inner layer that prevents expansion? I have never cut through one to see.
#12
The most likely cause of this walking is the incorrect installation of the sprockets. Check your work against a factory diagram to see if you haven't inadvertently swapped one of the sprockets that has a shoulder towards the front for one with the shoulder towards the rear.
gb
gb
#13
Drifting
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George is right about this. One our 84 track car, after a belt job with new cam seals also, A seal was turned wrong. This caused the belt to "walk" foward. Take the sprocket back off and do like George said and check to make sure everything is put back together right. Get a good digram that shows how it goes back together.
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Originally Posted by 944Ecology
The most likely cause of this walking is the incorrect installation of the sprockets. Check your work against a factory diagram to see if you haven't inadvertently swapped one of the sprockets that has a shoulder towards the front for one with the shoulder towards the rear.
gb
gb
#15
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Another possible issue here is the head work that was previously performed. It's possible that when the head was milled flat it may not have been perfectly square to the cam.
A little extra info for those playing at home...... Kevin's last belt did this as well.
A little extra info for those playing at home...... Kevin's last belt did this as well.