Locking Cams Really Necessary on an IMS Replacement?

[rennbob]

Forgive me I have several outstanding questions on my current IMS/AOS/clutch/FW DIY on my 99 996 C2...     I've read seemingly every post on every forum regarding the IMS replacement, but I'm still uncertain if I can safely shortcut locking the camshafts if I ensure that the crank is locked at TDC and the two bottom tensioners are out.    

 

I've spoken to a few Bay Area Porsche mechanics who say they never lock the camshafts, but of course the full instructions from LNE says to lock.    I will err on the side of caution (lock), but would like to skip the step if it's truly not required.   My 99 should be a 5 chain motor, which I understand is even less likely to skip a tooth during the operation....   

 

If I lock, can I just lock the exhaust CAM (or intake, whichever is directly connected to the IMS) since exhaust/intake have their own chain?  Or does the LNE lock tool force me to lock both exhaust and intake?  

 

Or perhaps I could I just lock one bank's camshafts, and not the other bank?

 

Thanks.

Edited September 15, 2014 by rennbob

[JFP in PA]

Forgive me I have several outstanding questions on my current IMS/AOS/clutch/FW DIY on my 99 996 C2...     I've read seemingly every post on every forum regarding the IMS replacement, but I'm still uncertain if I can safely shortcut locking the camshafts if I ensure that the crank is locked at TDC and the two bottom tensioners are out.    

 

I've spoken to a few Bay Area Porsche mechanics who say they never lock the camshafts, but of course the full instructions from LNE says to lock.    I will err on the side of caution (lock), but would like to skip the step if it's truly not required.   My 99 should be a 5 chain motor, which I understand is even less likely to skip a tooth during the operation....   

 

If I lock, can I just lock the exhaust CAM (or intake, whichever is directly connected to the IMS) since exhaust/intake have their own chain?  Or does the LNE lock tool force me to lock both exhaust and intake?  

 

Or perhaps I could I just lock one bank's camshafts, and not the other bank?

 

Thanks.

 

Absolutely it is necessary.  Taking short cuts on an IMS retrofit is a recipe for disaster; most of the ones we see that have gone bad did so because those doing the swap did not follow the LN proceedures to the letter.

[rbrindley1]

I agree with JFP. In addition you have made the choice to go with the LN retrofit, the industry leading solution, therefore, follow through with the best practice for installation. They develop the procedure for a reason. You do not want to find out the hard way the cams shifted for some reason....a preventive expense in your investment will become a reaction expense.

[Domiac]

I've spoken to a few Bay Area Porsche mechanics who say they never lock the camshafts, but of course the full instructions from LNE says to lock.    I will err on the side of caution (lock), but would like to skip the step if it's truly not required.   My 99 should be a 5 chain motor, which I understand is even less likely to skip a tooth during the operation....   

 

If you can, have your Bay Area Porsche mechanics answer to the following question: "Have you ever replaced IMSB?" If you asked this from Porsche dealership mechanics, they are even not allowed to do such retrofits.

 

Both LN and Pelican insists that IMS needs to be secured before replacing the bearing.

[Silver_TT]

 

If you asked this from Porsche dealership mechanics, they are even not allowed to do such retrofits.

 

 

 

FYI - I think this might depend on the dealer.  The dealer I used sometimes previously (before I moved) would do LN IMSB installs and even strongly recommended it.  They aren't an authorized shop to do it, but they would do them.

 

They also installed the 2nd gear pop-out detent from Gbox in my 911 Turbo and, while they are more than happy to take the tranny work, they highly recommend Gbox and respect Stan.  They are very reasonable people in my opinion....however, I've read about other dealers in other places that couldn't be more different (ie. void warranties if they saw your car at a PCA track event, etc as some folks have claimed in the past).

 

And last, don't even think about skipping steps and not locking the cams.  Lot of not so great mechanics out there.  Those guys that are skipping steps on these........I would not want them touching my car, that's for sure.

Edited September 16, 2014 by Silver_TT

[rennbob]

I didn't mean for this to be a contentious topic.   I have now had a chance to read the LN instructions, hopefully locking the cams won't add to much time and I will follow the instructions exactly.   

 

A few follow-on questions:

 

1)  I found posts from Jack Raby saying locking the crank at TDC OR TDC Overlap is OK--either position will unload the IMS as all cam lobes are off the valves.     But maybe the cam lock tool will only go in properly when I am truly on TDC?  

 

2)  To confirm, the camshafts in only one bank [cyl 1-3, drivers side USA 996, lower tensioner on flywheel side, cam plugs on crank pulley side] needs to be locked? 

 

3)  Still need to remove my flywheel.  Thoughts on using an impact gun?   I am currently planning on fab'ing a lock tool and using my breaker bars.  However, have recently bought an impact gun...

[Silver_TT]

Nothing controversial about it -- If you follow the LN instructions you will be fine.  It's been done thousands of times using those steps so they are tried and true, so to speak.  The tool should only go in when you are at TDC.  It's just a little metal bracket that will only go in when those are lined-up (TDC).  Don't know about the impact gun, I would get JFP to answer that one.  I generally don't use an impact gun on my car but I have also never removed the flywheel.  Good luck with the job!

[Domiac]

1)  I found posts from Jack Raby saying locking the crank at TDC OR TDC Overlap is OK--either position will unload the IMS as all cam lobes are off the valves.     But maybe the cam lock tool will only go in properly when I am truly on TDC?  

 

To my understanding this cannot be true, there's always load in either bank 1 or 2 when you put locking pin to crank pulley (TDC Zyl #1) you are either

 

1) TDC compression #1 meaning

- Cyl #1 TDC compression, has no valves open

- Cyl #6 compression stage, all valves closed

- Cyl #2 intake stage, has intake valves open (STRESS on bank 1)

- Cyl #4 TDC overlap, no valves open (under overlap)

- Cyl #3 exhaust stage, has exhaust valves open (STRESS on bank 1)

- Cyl #5 power stage, all valves closed

 

or

 

2) TDC overlap for Cyl #1 meaning

- Cyl #1 TDC overlap, no valves open (under overlap)

- Cyl #6 exhaust stage, has exhaust valves open (STRESS on bank 2)

- Cyl #2 power stage, all valves closed

- Cyl #4 TDC compression, has no valves open

- Cyl #3 compression stage, all valves closed

- Cyl #5 intake stage, has intake valves open (STRESS on bank 2)

 

I have personally turned crank multiple times and observed how valves move on each cylinder.

[Domiac]

Here's a rough draft regarding cylinder stages that I did during my IMS / .. maintenance:

 

 

 

[rennbob]

Thanks guys for the replies.   Any other opinions on flywheel bolts?   I think I might at least use the gun to get the bolts off, and then torque by hand when reinstalling.  

 

Regarding TDC this is the quote I was referring to on another forum (search for "not another ims thread").   It was good to re-read it.

 

>> This is where experience from other engines isn't beneficial.. If you attend my engine rebuild school you'll learn that at TDC EVERY VALVE in the M96 is "off lobe".

>> The engine was designed in this manner and all camshafts are relaxed at this point.

 

Domiac I see what you're saying, but either way I'll pin my crank, lock my cams, pull my tensioners and hopefully the job will go well.  

[AWDGuy]

I can't comment about the Porsche engine specifically but I've always used an impact to REMOVE the fly wheel bolts.

[Domiac]

Thanks guys for the replies.   Any other opinions on flywheel bolts?   I think I might at least use the gun to get the bolts off, and then torque by hand when reinstalling.  

 

Regarding TDC this is the quote I was referring to on another forum (search for "not another ims thread").   It was good to re-read it.

 

>> This is where experience from other engines isn't beneficial.. If you attend my engine rebuild school you'll learn that at TDC EVERY VALVE in the M96 is "off lobe".

>> The engine was designed in this manner and all camshafts are relaxed at this point.

 

Domiac I see what you're saying, but either way I'll pin my crank, lock my cams, pull my tensioners and hopefully the job will go well.  

 

All I am saying is that when you pin your crank Zyl #1, you have either bank 1 or bank 2 relaxed, never both. Observe the exhaust cam locking "moons" from this thread: http://www.renntech.org/forums/topic/46354-tdc-cyl-1-for-a-3-chain-996-2004-36l/?hl=domiac#entry252752

 

It can very well be that at some other point (but not on Zyl #1 mark ever), one can get into such position where there is no tension in any banks.

[rennbob]

Interesting thread.   So this means that I need to find overlap TDC #1 for the IMS procedure on my 5-chain motor?    The LN tool should only lock in this one way, correct?   

 

 

1) Crank clockwise until overlap TDC #1 is seen

- cyl #1 exhaust has just closed, cyl #1 intake is just about to open

- cyl #6 exhaust open, cyl #5 intake open

- bank 1 smaller circular cutouts are pointing away from the engine (or when looking at bank 1 and intake camshaft is above and exhaust camshaft is below, then smaller circular cutouts are on the left side, larger cutouts on the right side)

 

2) Lock bank 1

[Domiac]

Interesting thread.   So this means that I need to find overlap TDC #1 for the IMS procedure on my 5-chain motor?    The LN tool should only lock in this one way, correct?   

 

 

1) Crank clockwise until overlap TDC #1 is seen

- cyl #1 exhaust has just closed, cyl #1 intake is just about to open

- cyl #6 exhaust open, cyl #5 intake open

- bank 1 smaller circular cutouts are pointing away from the engine (or when looking at bank 1 and intake camshaft is above and exhaust camshaft is below, then smaller circular cutouts are on the left side, larger cutouts on the right side)

 

2) Lock bank 1

 

That should be correct. You should only be able to put your locking tool for bank 1 when engine is on overlap TDC for cylinder #1. It can require a bit finesse to get the tool in as the tolerances are quite tight. Take your time and if it does not fit the first time, turn another 359 degrees (always clock-wise only) and the soonest you approach 360 degrees try fitting your locking tool again. I had to gently "tap" my crank back and forth (within less than a degree) in order to get the locking tool secured.

 

As you can see the "half moons" are alternating their position per every 360 degrees, one is overlap TDC #1 and another compression TDC #1.

 

Please follow LN's instructions to the letter if you have LN's bearing.

 

Have fun and good luck!

[JFP in PA]

You need to hand rotate the engine to TDC (clockwise rotation only), at which point the crank locking pin will just slide into the engine's crank pulley and the boss on the engine case.  This locks the crank from moving.  Then remove the cam plugs on the cylinder head facing away from the flywheel and insert and bolt down the cam locking tool.  At this point, nothing can move and you are safe to pull the tensioners out per the LN instructions and move foward with the IMS retrofit.

 

You can use an impact to remove both the pressure plate and flywheel bolts as they will not be reused.  Do not use an impact on the IMS flange bolts.  Do not use the impact to reinstall any of the bolts, use a torque wrench.

[rennbob]

Now I'm confused:   "Then remove the cam plugs on the cylinder head facing the flywheel".    Facing the flywheel, the visible plugs are on the left, which is Bank 2, no?    Don't I want Bank 1 cam plugs, near the alternator? 

 

I've already done a trial run with finding TDC (or TDC overlap) and locking it with a 5/16 pin.   No problem.    But I may have to rotate 360 several times to get the tool to lock? 

[JFP in PA]

Now I'm confused:   "Then remove the cam plugs on the cylinder head facing the flywheel".    Facing the flywheel, the visible plugs are on the left, which is Bank 2, no?    Don't I want Bank 1 cam plugs, near the alternator? 

 

I've already done a trial run with finding TDC (or TDC overlap) and locking it with a 5/16 pin.   No problem.    But I may have to rotate 360 several times to get the tool to lock? 

 

Sorry, you are correct, I meant to say  "cam plugs facing away from the flywheel".

 

It is not uncommon to have to rotate the engine more than one cycle to get the cams to line up when the engine is at TDC.

[rennbob]

Cool.  Thanks.    I will post the status over the next week or two!

[987_RDC]

Dead blow hammer and freeze the bearing.

[rennbob]

Took 5 min to pull the FW with the gun.  Behind it found a surprise, the oil leak looks to be from the IMS flange, not the RMS.   RMS is old style (it was replaced 2X under warranty).   I had already ordered a new RMS, and have access to the Porsche install tool.  

 

Should I leave well enough alone or replace the RMS?!

 

While waiting for parts I've started scoping the AOS, can really only get one arm in the space at a time.  Having second thoughts, I don't wan't to get stuck halfway with those !@##$ hose clamps.   The AOS is still functional, although still leaking a bit from the bellows.  I suppose I would replace the coolant hose clamps with worm type.  

 

Anyone know a local Bay Area CA source for Loctite 574 or Curil-T? 

 

 

100k mile flywheel passed movement and return-to-center test with flying colors, but there's a lip and the worn face doesn't feel perfectly flat.   Ordered a new one.

 

 

And dead blow hammer already purchased and freezer is anxiously awaiting the bearing!

 

[Dennis Nicholls]

For locking the flywheel....I used a spare 10mm bolt into one bellhousing bolt hole and a 2 foot Harbor Freight pry bar inserted into a starter ring tooth gap.  Previously I'd radiused the end of the pry bar to fit snugly into such a gap.  Here it is in the "bolt torqueing" direction.  The end of the pry bay is off the screen but supported by some blocks - the rotation of tightening pushes the handle end downwards.

 

[JFP in PA]

Took 5 min to pull the FW with the gun.  Behind it found a surprise, the oil leak looks to be from the IMS flange, not the RMS.   RMS is old style (it was replaced 2X under warranty).   I had already ordered a new RMS, and have access to the Porsche install tool.  

 

Should I leave well enough alone or replace the RMS?!

 

While waiting for parts I've started scoping the AOS, can really only get one arm in the space at a time.  Having second thoughts, I don't wan't to get stuck halfway with those !@##$ hose clamps.   The AOS is still functional, although still leaking a bit from the bellows.  I suppose I would replace the coolant hose clamps with worm type.  

 

Anyone know a local Bay Area CA source for Loctite 574 or Curil-T? 

 

photoa.jpg

photo 2.JPG

 

100k mile flywheel passed movement and return-to-center test with flying colors, but there's a lip and the worn face doesn't feel perfectly flat.   Ordered a new one.

 

photo 3.JPG

 

And dead blow hammer already purchased and freezer is anxiously awaiting the bearing!

 

We always replace the RMS once you get that far in, the newer PTFE design is much better than the old style seals.  I would also do the AOS.

[rennbob]

Thanks for all the help so far guys.

 

Bearing is out without issue.   I notice a few marks on the outer race (see pics)...   Do I really need any bearing retaining compound for the new one?  Or do they all pretty much look like this?    The old bearing looks and feels like new otherwise.   I want to to finish this up!

 

 

 

 

 

[JFP in PA]

Thanks for all the help so far guys.

 

Bearing is out without issue.   I notice a few marks on the outer race (see pics)...   Do I really need any bearing retaining compound for the new one?  Or do they all pretty much look like this?    The old bearing looks and feels like new otherwise.   I want to to finish this up!

 

photo 1.JPG

photo 2.JPG

 

Pull the seals off the bearing and see if there is any grease still in it.

 

You should not need any retaining compounds on the new bearing as it should be an interference fit.  I would however look that the inside of the shaft to see if it has similar marks.

[rennbob]

So just skip the bearing compound?  Do you ever use it for the IMS at your shop? 

 

Reading the LN instructions and a post by Raby, they say "consider" using bearing compound if there are signs of movement / ovality in the s_haft.   It likely moved a little up/down as there are a few smaller marks 180 degrees from the ones shown.   But then it's gone 100k miles and doesn't look like it has spun in the sha_ft.  I'd prefer not to use compound as it could make installation and removal more difficult.     

 

The bearing is full of oil, no grease.  The inside of the IMS looks OK, no marks.  

 

In the meantime, look what fell out:     :)