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Discussion summary
YOUR RESEARCHChanging IMS bearing
Leading reported evidence
Replace chain tensioners if worn
Suggestion or failed attempt
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Suggestion · Original poster
In LN engineering's instructions they say that you should replace the chain tensioners if worn.
Leading evidence: 'Replace chain tensioners if worn' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace chain tensioners if worn' (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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Suggestion · Original poster
I am about to change the IMS bearing on my 996 C2 2002.
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Suggestion
Then, with the tensioners back in place, rotate the engine a couple of revolutions using a breaker bar on the main pulley.
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Hello
I am about to change the IMS bearing on my 996 C2 2002. The gearbox is out
and it was acctually a quite undramatic event (after I managed to remove the top bolt between the gearbox and the engine).
I have read some contradictory instructions. In LN engineering's instructions they say that you should replace the chain tensioners if worn. In Pelicanparts instructions they say that you shouldn't remove the chain tensioners completely since that could result in that the chains need to be timed.
So my question is, is it safe to remove the chain tensioners as long as you have locked the cam shafts? I couldn't see that Pelicanparts acctually locked the cam shafts in their instructions and maybe that is the reason for the conflicting instructions?
Robert
I'd never do the job with tensioners in place. Doing so is much more likely to create cam timing deviations as the chains remain loaded. We have carried out this task about 230 times thus far and have only had one engine end up with compromised timing, but it came to us part way through the procedure as a problem child. Follow the directions that come with the bearing kit you purchased-
Pull them, and verify timing afterwards (once they are back in). It would be silly to start the engine without verifying the timing. A few tens of dollars for some cam covers is cheap insurance for a chain that slipped during procedure.
Wayne's procedure is somewhat different from LNE's, since he has invented a way to pin the IMS shaft from moving while the engine is not at TDC. Pelican's kit is still not available for sale...
The problem with that is once it is utilized you are ASSUMING that the cam timing is correct when the procedure is initiated. In engine building the first rule that we learn from practical application is to NEVER assume ANYTHING and to quantify everything. Of course, one has to have built an engine to understand this.
The LNE procedure came from practical application experience.
Engine pinned at TDC, cams locked, yes go for it. Good for you by following the LNE instructions WORD FOR WORD and locking the cam shafts. Many people have "skipped" this step, with your 3 chain engine it's much more imperative (less so with a 5 chain).
+1
pin it, lock the cams then take them out. You don't want to try and save 30 min and end up with hours trying to re-time the cams, I have seen it before.
My thought is why make things harder down the road. That is why when I do an engine or a big job I take my time with the diss-assembly, cleaning and organizing, it makes going back together a lot better.
EVERY issue I have ever had to help someone solve with tech support has been created by not reading or following directions, OR not taking the time to do the job correctly.
Disassembly is MORE IMPORTANT than any other aspect of the retrofit process. I have had to bail many people put of trouble because they rush or don't pay attention.. No free lunches here, if I have to bail you out its gonna cost.
You did lock the cams, right?
That means you have the cam covers off. To lock them you must be at TDC, so the cams should be perfectly vertical. To verify timing afterwards, make sure they're still perfectly vertical. Then, with the tensioners back in place, rotate the engine a couple of revolutions using a breaker bar on the main pulley. Make sure you don't have interference.
To be 100% sure you'd want to take measurements with a durometric before and after.
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