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Timing Sprocket Alignment by gem1138
Started on: 10-18-2013 03:57 PM
Replies: 6 (148 views)
Last post by: Blacktree on 10-19-2013 03:30 PM
gem1138
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Report this Post10-18-2013 03:57 PM Click Here to See the Profile for gem1138Click Here to Email gem1138Send a Private Message to gem1138Edit/Delete MessageReply w/QuoteDirect Link to This Post
I thought when I got to the point of installing the new timing chain and sprockets on my 88gt that the proper alignment of the sprockets would obvious. I sure don't want to screw this part up so I am asking even if it is a stupid question. At this time, I have both old sprockets removed. My timing had jumped so I know the relative positions of the crank and cam shafts are not right. Can someone please show me a helpful photo or describe the answer?
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Report this Post10-18-2013 04:16 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is a small dot on each sproket, on the smaller one it is on a tooth and on the large one it is between two teeth. They point to each other. Larry
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gem1138
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Report this Post10-18-2013 05:04 PM Click Here to See the Profile for gem1138Click Here to Email gem1138Send a Private Message to gem1138Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks Larry,
Looking at the sprockets I see that the original large on has sort of a mirror image tooth for a mark the matches the dot on the new one. The old and new small sprockets are identical minus wear. On all of these sprockets, the marks are centered on the teeth. I will proceed with them facing each other as you say.
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Pyrthian
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Report this Post10-18-2013 05:13 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianEdit/Delete MessageReply w/QuoteDirect Link to This Post
and - a fun tip: when them 2 dots are pointing at each other and the chain guard mark - that is TDC #4 - NOT TDC#1

TDC #1 is when both dots are at the very top.
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Bloozberry
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Report this Post10-18-2013 07:49 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here's a pic from my collection. You'll note that because it's a chain drive, that both dots are on the teeth (not one on a tooth and one on a valley as Larry mentioned). The dots are only as he specified when it is a direct gear drive without a chain.

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Bloozberry
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Report this Post10-18-2013 08:08 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
And here's a photo of an '88 engine I overhauled a couple years ago. You'll note that the new timing gear set didn't have a dot on the cam sprocket, but rather a cast nib. The dot on the crank sprocket isn't visible in this photo.

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Blacktree
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Report this Post10-19-2013 03:30 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pyrthian and Bloozberry are both right. That said, it's your call whether you want to set the timing for TDC #1 or #4. Just remember to set the distributer accordingly.

And after you install the timing chain, you can turn the engine manually to whichever spot you want. So, for example, you could install the gears with the marks facing each other, then rotate the crankshaft one turn to put it at TDC #1.
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