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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHNeed help with 996.1 cam timing procedure
Leading reported evidence
Adjust with the tensioners installed
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Performed · outcome unconfirmed · Original poster
I went back and reviewed my cam timing procedure and it did show the timing to be adjusted with the tensioners installed.
Leading evidence: 'Adjust with the tensioners installed' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust with the tensioners installed' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
The position was checked with the tensioners back in.
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Performed · outcome unconfirmed
Just changing the small pads only brought it down to ~5 degrees, so I removed the scavenge pump, ran the engine on the durametric and dialed in the sproket bolts bringing it to less than 2 degrees.
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Suggestion · Original poster
I will now do Bank 2 and then double check the timing in both banks.
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Suggestion · Original poster
So I left it at that and went on to replace the IMS bearing (that also went well).
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Suggestion
Just changing the small pads only brought it down to ~5 degrees, so I removed the scavenge pump, ran the engine on the durametric and dialed in the sproket bolts bringing it to less than 2 degrees.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
Just changing the small pads only brought it down to ~5 degrees, so I removed the scavenge pump, ran the engine on the durametric and dialed in the sproket bolts bringing it to less than 2 degrees.
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
However, when the IMS work was complete I rechecked the cam timing and it was off on both banks, So I went back through the cam timing procedure and set both banks to the correct timing.
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Suggestion
My first thought was you installed the bearing and still had the tensioners out while setting the timing, then when you adjusted and tightened down the sproket it was on a slack chain, so verify that first.
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3 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T135432Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have the engine out of my 2000 996.1 C4 6-spd manual with 77,000 miles. I have completed the replacement of the cam-to-cam chains, the VarioCam guide pads and the two chain guides on the cam to IMS shaft chains. The wear on the VarioCam guides was quite bad (but no large pieces missing). The long chain guides had minimal wear. The motivation for this work was cam deviation of -9.59 deg. on Bank 1 and -4.13 deg. on Bank 2. The work progressed well (replacement and cam timing) but when I had the timing adjustment complete I did notice the the four adjustment hold-down bolts on the cam sprocket were between the center and the end of their adjustment travel. So I left it at that and went on to replace the IMS bearing (that also went well). However, when the IMS work was complete I rechecked the cam timing and it was off on both banks, So I went back through the cam timing procedure and set both banks to the correct timing. However, when completed, the cam sprocket bolts on both banks were now at the end of their adjustment travel (but still in time.)
So my question: 1) what caused the timing to shift during the IMS bearing replacement work (I am pretty sure, but not 100% sure they were ok when I finished the timing work), and 2) should I now, while the engine is out, remove the cam covers and shift the cam sprockets one chain link? Your comments would be greatly appreciated.
Since no one else responded I'll take a shot.
My first thought was you installed the bearing and still had the tensioners out while setting the timing, then when you adjusted and tightened down the sproket it was on a slack chain, so verify that first. I did my bank one a couple years ago (engine in) when it showed a deviation of ~7 degrees (bank 2 was only 1 degree). Just changing the small pads only brought it down to ~5 degrees, so I removed the scavenge pump, ran the engine on the durametric and dialed in the sproket bolts bringing it to less than 2 degrees. When adjusting the sproket, just one mm equals about 1 degree of timing so it's fairly sensitive to getting it right. The picture below is my final setting before I put the scavage back on. As you can see it is very close to centered and only a couple mm off from what the factory setting was before I started.
To answer your question, yes, To correctly time, I think your sproket bolts should be very close to the center of their range, within a few mm. If set all the way in the slot it looks like you might be off a tooth.
DCS800. Thank you very much for your comments. I went back and reviewed my cam timing procedure and it did show the timing to be adjusted with the tensioners installed. So I am unsure exactly what happened. In any case, I decided to remove the cam covers and slip the chain on the cam sprocket. I have completed this on Bank 1 and I found that slipping the chain one link places the cam sprocket short of center. Two links places it just past center. The position was checked with the tensioners back in. So I left it at the two link placement. This will give me sufficient adjustment range. I will now do Bank 2 and then double check the timing in both banks. The cam cover removal and replacement was a bit of work but not all that bad with the engine out.
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