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Timing after belt break

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Old Jan 31, 2014 | 04:00 AM
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From: Peoria AZ
Timing after belt break

Hi guys. I recently bought a 93 V6 with a broken timing belt. I have it all taken apart and I've been reading through a few walkthroughs posted here. I wanted to confirm I just need to line up the top pulleys with the paint markers and the crank sprocket with the tick at 12:00 to get the timing right.

If I read things right, the #1 cylinder will be at TDC on the compression stroke as link as the paint mark is lined up. Is that right?
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Old Jan 31, 2014 | 06:20 AM
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Yes it is.
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Old Jan 31, 2014 | 06:52 AM
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Thanks! If I can get all the parts in today, I hope to put it all together and fired up tonight.
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Old Jan 31, 2014 | 07:21 AM
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I might be wrong but is it not possible for the crank to be out 180 degrees when at the 12 o'clock position? Meaning that #1 might not be at TDC?
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Old Jan 31, 2014 | 07:45 AM
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Originally Posted by Marc
I might be wrong but is it not possible for the crank to be out 180 degrees when at the 12 o'clock position? Meaning that #1 might not be at TDC?
No. TDC is TDC. That's what the marks indicate.

Most of the confusion comes from where the FSM tells you to "SET NO.1 CYLINDER TO TDC/COMPRESSION". Which is saying too much really. It should just tell you to set the No.1 cylinder to TDC. Since TDC can be compression or exhaust, stroke wise. What makes it compression or exhaust is the valve timing.
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Old Jan 31, 2014 | 07:46 AM
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Being 180 degrees out of phase was my concern. Maybe i should have stated this better. The write ups I found were for a regular replacement, not for a break so I was hoping to get clarification.

By the way, I found a bunch of loose bearings (I think) between the bottom of the crankshaft timing pulley and the bottom lip of the engine cover. I think the rubbing is what caused the belt to break. The #1 idler pulley looks like it was recently replaced. Anyone ever see the bearings fall out when a idler goes out?
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Old Jan 31, 2014 | 07:47 AM
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Originally Posted by MudHippy
No. TDC is TDC. That's what the marks indicate.

Most of the confusion comes from where the FSM tells you to "SET NO.1 CYLINDER TO TDC/COMPRESSION". Which is saying too much really. It should just tell you to set the No.1 cylinder to TDC. Since TDC can be compression or exhaust, stroke wise. What makes it compression or exhaust is the valve timing.
Thanks for the clarification. Exactly what I was hoping to hear.
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Old Jan 31, 2014 | 07:56 AM
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Originally Posted by DannyD
Anyone ever see the bearings fall out when a idler goes out?
I haven't seen it first-hand. But I have heard of it happening. So you're probably right in your presumption.
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Old Jan 31, 2014 | 12:47 PM
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Originally Posted by MudHippy
No. TDC is TDC. That's what the marks indicate.

Most of the confusion comes from where the FSM tells you to "SET NO.1 CYLINDER TO TDC/COMPRESSION". Which is saying too much really. It should just tell you to set the No.1 cylinder to TDC. Since TDC can be compression or exhaust, stroke wise. What makes it compression or exhaust is the valve timing.
I think I got it. If you had a properly setup timing belt THEN it would be possible to be at TDC AND not be on the compression stroke?
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Old Jan 31, 2014 | 02:30 PM
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Not if it was "properly" set up.

The crank turns twice for each turn of the cam. By definition, cylinder one is on the top of the compression stroke (both valves are closed) when the cam pointer points up. After one turn of the crank, the cam pointer is now pointing down (1/2 turn), and cylinder one is now at the top of the exhaust stroke.
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Old Jan 31, 2014 | 04:08 PM
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Originally Posted by scope103
Not if it was "properly" set up.

The crank turns twice for each turn of the cam. By definition, cylinder one is on the top of the compression stroke (both valves are closed) when the cam pointer points up. After one turn of the crank, the cam pointer is now pointing down (1/2 turn), and cylinder one is now at the top of the exhaust stroke.
My bad. I meant to say TDC as indicated by the notch on the harmonic balancer. Would that be correct then?
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Old Jan 31, 2014 | 04:14 PM
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The crank turns twice (to get four strokes). So the mark on the harmonic balancer is lined up at the top of the compression stroke (what people most often mean when they say TDC), and again at the top of the exhaust stroke.

With your clarification, I'm pretty sure you've got it correctly.
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