IMS Install help! IMS bearing not centered

[gonzojive]

I am in a similar situation as others in this thread except that I have not yet extracted the original bearing. I have set screws in place but the bearing is off-center. Only 2 of the 3 tensioners are out. Some ideas for getting the job done from here:

1) Remove 3rd tensioner in attempt to center the bearing in the case hole. Is there significant risk of a timing slip from removing the third tensioner? I have an '01, 5-chain engine.

2) Try to get the engine to TDC, then use cam lock (which came with the ln retrofit kit) and follow ln engineering instructions from the top. To do this, the idea is to reinstall the tensioners and then rotate the engine manually to TDC. JFP stated this is unlikely to work because the flange from the ims bearing is no longer being held in place by the cover. In my case, the old ims bearing is still installed, so I think I have two options to keep it centered while I move to TDC:

a) reinstall the cover. Since the flange is now off-center I'm not sure if this will work. Plus, the flange is broken and would not be able to be secured from the outside of the engine case.

b) use the LN easy-out tool in combination with the removal tool to keep the IMS centered while reinstalling the tensioners and rotating the engine to TDC.

Any feedback on these approaches? I am especially curious about what the risks are when removing the third tensioner--I don't want to mess up the timing.

Image below. FYI, the set screws are just m6 bolts with their heads chopped off:

[Jake Raby]

Originally Posted by gonzojive

I am in a similar situation as others in this thread except that I have not yet extracted the original bearing. I have set screws in place but the bearing is off-center. Only 2 of the 3 tensioners are out. Some ideas for getting the job done from here:

1) Remove 3rd tensioner in attempt to center the bearing in the case hole. Is there significant risk of a timing slip from removing the third tensioner? I have an '01, 5-chain engine.

2) Try to get the engine to TDC, then use cam lock (which came with the ln retrofit kit) and follow ln engineering instructions from the top. To do this, the idea is to reinstall the tensioners and then rotate the engine manually to TDC. JFP stated this is unlikely to work because the flange from the ims bearing is no longer being held in place by the cover. In my case, the old ims bearing is still installed, so I think I have two options to keep it centered while I move to TDC:

a) reinstall the cover. Since the flange is now off-center I'm not sure if this will work. Plus, the flange is broken and would not be able to be secured from the outside of the engine case.

b) use the LN easy-out tool in combination with the removal tool to keep the IMS centered while reinstalling the tensioners and rotating the engine to TDC.

Any feedback on these approaches? I am especially curious about what the risks are when removing the third tensioner--I don't want to mess up the timing.

Image below. FYI, the set screws are just m6 bolts with their heads chopped off:

This is a very poor method of securing the IMS during the procedures.

Have you pulled the other two tensioners completely from the engine? Were you on TDC when you began the procedure?

How did you break the flange?

[gonzojive]

Originally Posted by Jake Raby

This is a very poor method of securing the IMS during the procedures.

Have you pulled the other two tensioners completely from the engine? Were you on TDC when you began the procedure?

I am certainly not disagreeing with you there - should have at least ordered proper set screws. I followed the Pelican Parts guide that uses set screws and doesn't call for starting from TDC.

I was not on TDC when I began the procedure. I initially removed both tensioners completely, though they are now partly screwed in.

Originally Posted by Jake Raby

How did you break the flange?

Flange is partly broken because I cut off the nut that was attached to it outside of the engine case. I was not able to rotate the nut with respect to the flange and eventually cut it off because the flathead end of the flange was stripped.

[Jake Raby]

Originally Posted by gonzojive

I am certainly not disagreeing with you there - should have at least ordered proper set screws. I followed the Pelican Parts guide that uses set screws and doesn't call for starting from TDC.

I was not on TDC when I began the procedure. I initially removed both tensioners completely, though they are now partly screwed in.



Flange is partly broken because I cut off the nut that was attached to it outside of the engine case. I was not able to rotate the nut with respect to the flange and eventually cut it off because the flathead end of the flange was stripped.

Wow... You couldn't hold the center stud while breaking torque on the center nut? Why?

Not starting at TDC is a recipe for disaster. The load from the cams is way too much and overcomes those measley little screws in a heartbeat.

There's one crank position where ALL the cams are unloaded, and that's at TDC.

You will not return the IMS to center withoutbremovingvthe loads from it, so you can't get the flange back on to rotate back to TDC; because you can't center it for re installation.

You now have to re- time the engine from scratch, just like everyone else who pulls the flange at any crank position other than TDC.

I developed the simplest procedure for this, it's been adopted by around 30,000 installers and you never see this post from folks that follow it.

[gonzojive]

Thanks a ton for your help.

Originally Posted by Jake Raby

Wow... You couldn't hold the center stud while breaking torque on the center nut? Why?

Your understanding is correct. The nut was stuck to the stud. I'm not sure why it was stuck on so tight.

In part I damaged the stud head because I initially used a screwdriver that was too small and stripped the slot. I tried larger screwdrivers and holding the stud head with vice-grips but could not break torque that way. I was stuck on this step for a few days.

One data point, not sure how relevant: The inside of the transmission is very dirty, and it's an '01... perhaps this contributed to the tightness.

Originally Posted by Jake Raby

Not starting at TDC is a recipe for disaster. The load from the cams is way too much and overcomes those measley little screws in a heartbeat.

There's one crank position where ALL the cams are unloaded, and that's at TDC.

Thanks for this warning to future readers. Had I read this advice before the install I would have done it the way you describe.

Originally Posted by Jake Raby

You will not return the IMS to center without removing the loads from it, so you can't get the flange back on to rotate back to TDC; because you can't center it for re installation.

There are a few things I don't understand here:

1) What is the nature of the load being put on the IMS? Is it bad for any engine component to apply a force opposite to this force?

2) Why is it important that the bearing is centered when rotating back to TDC?

3) In my first post I proposed using the removal tool to center the bearing by overcoming the force from the cams. The large cylinder part of the removal tool could be used to keep the bearing centered while moving the engine back to TDC. What are the issues with this approach?

Originally Posted by Jake Raby

You now have to re- time the engine from scratch, just like everyone else who pulls the flange at any crank position other than TDC.

Can you help me understand what exactly has gone wrong that requires retiming from scratch? Have I likely already let the chains slip (even with my 5-chain engine)?

Also, to "re-time from scratch," is it necessary to drop out the engine and take it apart?

[Jake Raby]

There are a few things I don't understand here:

1) What is the nature of the load being put on the IMS? Is it bad for any engine component to apply a force opposite to this force?

Whats holding the IMS sideways in the bore is the timing chain for bank 1. That chain has load because at least one pair of cam lobes on that bank are opening valves. If you force the IMS sideways, you are stretching a chain thats already known to stretch and break. I have the only matter linked chains in the world, but they are far from cheap, if you ever need one. Also, never force anything within an engine, if it doesn't want to budge, you must find whats necessary and relieve the tension. If not, you'll be sorry.

2) Why is it important that the bearing is centered when rotating back to TDC?

Because rotating the engine ANY from the point you are at now will make the cam timing even worse, and you can crash valves into pistons. You can't get the flange back on to support the IMS, because its no longer centered in the bore, so rotating an unsupported IMS is a recipe for bigger disaster.

3) In my first post I proposed using the removal tool to center the bearing by overcoming the force from the cams. The large cylinder part of the removal tool could be used to keep the bearing centered while moving the engine back to TDC. What are the issues with this approach?

I invented and developed that tool, this was never its intended purpose. That said, you do not know how far out the cams are at the present, and you won't know if things will crash until you move the engine. Not saying this won't work, but I am saying that its not a smart approach.

Can you help me understand what exactly has gone wrong that requires retiming from scratch? Have I likely already let the chains slip (even with my 5-chain engine)?

The entire valve drive system has shifted when the flange was removed without the engine being at TDC and having the CAMS locked. Something had to move when the flange was removed, and its likely retarding bank 1. This means that the exhaust valves on that bank can crash into the pistons fairly easily, and you don't want to risk that.

Also, to "re-time from scratch," is it necessary to drop out the engine and take it apart?

No, it can be done in the chassis, engine assembled. Pull both cam covers, and have fun.

Now, do you guys see why we only sell our IMSR products through distributors supplying them to professionals? This sort of thing should be avoided at all costs, and this is not a job for the faint of heart. The learning curve is 90 degrees, and using a procedure that looks good on paper, is a lot different than one that was developed in the real world from trial and error.

I've made lots of errors, but thats what happens when you blaze the trail that leads to the super highway that everyone else decides to travel.

[gonzojive]

Originally Posted by Jake Raby

Whats holding the IMS sideways in the bore is the timing chain for bank 1. That chain has load because at least one pair of cam lobes on that bank are opening valves. If you force the IMS sideways, you are stretching a chain thats already known to stretch and break. I have the only matter linked chains in the world, but they are far from cheap, if you ever need one. Also, never force anything within an engine, if it doesn't want to budge, you must find whats necessary and relieve the tension. If not, you'll be sorry.


Because rotating the engine ANY from the point you are at now will make the cam timing even worse, and you can crash valves into pistons. You can't get the flange back on to support the IMS, because its no longer centered in the bore, so rotating an unsupported IMS is a recipe for bigger disaster.


I invented and developed that tool, this was never its intended purpose. That said, you do not know how far out the cams are at the present, and you won't know if things will crash until you move the engine. Not saying this won't work, but I am saying that its not a smart approach.


The entire valve drive system has shifted when the flange was removed without the engine being at TDC and having the CAMS locked. Something had to move when the flange was removed, and its likely retarding bank 1. This means that the exhaust valves on that bank can crash into the pistons fairly easily, and you don't want to risk that.

Thanks a lot for the explanations. I don't have a very mechanical background so I hope you'll excuse my perplexity.

In terms of forces acting on engine components, I'm not clear on why forcing the bearing back to center with the pull-out tool differs from the typical operation of the flange. Why would the forces from moving the bearing back to center stress the chain more than the usual?

I'm also pretty fuzzy on the shift you describe above when the flange was removed. How exactly would the timing get thrown off? During this shift, are you suggesting a sprocket has skipped a link in one of the camshaft-IMS chains? I'm not sure how the timing could be off otherwise.

Originally Posted by Jake Raby

No, it can be done in the chassis, engine assembled. Pull both cam covers, and have fun.

What steps are you recommending to re-time the camshafts, and where would replacing the IMS bearing fit into that procedure?

Before removing the cam covers, the Pelican Parts article on setting the camshaft timing says to put the engine at TDC and install the camshaft timing tool. This makes sense because the shaft is normally held in place by bearings built into the cover. I'm not currently at TDC, and you don't recommend rotating the crankshaft while the IMS isn't support. The timing tool only fits onto the camshaft heads at TDC, so I'm not sure how to proceed with safely removing either camshaft cover.