IMS install

[shadrach74]

So I've searched the forums and see conflicting info on my question.

This is my situation. My car is in for service (new clutch, axles, bypass pipes and IMSB). I went to visit my mech and he is in the process fo pulling the IMSB. He has the crank and cam positions marked, but is not locking the the cams at TDC.

According to the Pelican tech article the cams do not get locked.

According to my mechanic, it is impossible to lock the cams at TDC and lock the IMS sprocket because when the the cam and crank are at TDC, the set screw holes are lined up with holes in the IMS sprocket and therefore will not make contact with the sprocket thereby locking it in place.

For those of you that have done this procedure, is the Pelican tech article accurate? Is it the best way to do the IMSB replacement?

My mechanic tore is finger up pretty good loosening the rear tensioners, one was so tight that he needed a breaker bar and when it finally let go, his wrench slipped and he ended up with 5 stitches in his right ring finger. Now one of his shop mates will be continuing the job and I am nervous about the direction this is going.

Any feed back on locking vs not locking the cams would be appreciated.!

Thanks!

[Eric G]

You need to get the LN Engineering kit which has the cam locks. While technically you don't need to lock the cams as some have done...you risk your motor grenading should you jump a tooth.

So if you have a spare 18K laying around and feel lucky you can go this route. Otherwise for a small cost you can lock your engine and cams down, loosen and or replace your cam chain tensioners and be safe to proceed.

[Meir]

i think shadrach74 is trying to figure out, what is the best way to do that job.
if to be honest, i'm a little bit confused as well.
LN procedure say to lock the cams, and leave the IMS free.
in that case the shaft can go off-center and cause some deficolties with re installing the bearing.
on the pelican procedure, you use bolts to lock the IMS in place.



but you cannot lock the the cams at TDC.

which procedure is better? i don't know.
when the day will come (and its coming soon) i will probably go with the cam locking method instead of the IMS locking.
hoping not to end up like our buddy Hakim.
http://986forum.com/forums/diy-project-guides/37617-ims-install-problem.html

[JFP in PA]

If the engine is not locked at TDC, one or more valve springs are under compression and will try to rotate the engine when the tensioners are released. Do a search, Jake has commented on this multiple times. TDC is the only engine position where the springs to not load the cam drives. If the cams are unlocked and the engine is not locked at TDC, you risk the system jumping time when the tensioners are released. You may get away with doing it in this weird manor, but then again, you may not.............my guess is that you won’t.

[shadrach74]

Originally Posted by Meir

i think shadrach74 is trying to figure out, what is the best way to do that job.
if to be honest, i'm a little bit confused as well.
LN procedure say to lock the cams, and leave the IMS free.
in that case the shaft can go off-center and cause some deficolties with re installing the bearing.
on the pelican procedure, you use bolts to lock the IMS in place.



but you cannot lock the the cams at TDC.

which procedure is better? i don't know.
when the day will come (and its coming soon) i will probably go with the cam locking method instead of the IMS locking.
hoping not to end up like our buddy Hakim.
http://986forum.com/forums/diy-project-guides/37617-ims-install-problem.html

You nailed the essence of my question. The pelican article calls for the sprocket to be locked with set screws (AKA grub screws) using the threaded holes for for the IMS cover (as shown in the pick meir posted). The problem is the sprocket has holes in it as seen below.



There is no way to lock the IMS sprocket at TDS as the holes in the sprocket line up with the set screws in that position. TO lock the IMS sprocket, the set screws must contact the sprocket and not one of the sprocket holes. To put the IMS in a position where it can be locked means putting it somewhere other than TDC...

SO, should I lock the cams and ignore locking the IMS sprocket with the set screws? I cannot do both. This is the question I'm asking...

[JFP in PA]

Because the rear IMS sprocket is a press fit on the shaft, and can be dislodged with the set screws (a situation that cannot be corrected without taking the engine apart), I am not a big fan of the set screw method.

When the engine is locked at TDC, and the cams are locked off with the proper tool(s), nothing can move. With the tensioners removed, replacing the IMS bearing is straight forward, and without risk.

[Meir]

Originally Posted by JFP in PA

If the engine is not locked at TDC, one or more valve springs are under compression and will try to rotate the engine when the tensioners are released. Do a search, Jake has commented on this multiple times. TDC is the only engine position where the springs to not load the cam drives. If the cams are unlocked and the engine is not locked at TDC, you risk the system jumping time when the tensioners are released. You may get away with doing it in this weird manor, but then again, you may not.............my guess is that you won’t.

with that said, why Wayne came up with the screw locking method of the IMS ?
am i missing something in his great article?
and if i got JFP on the hook , i whould like to ask another question please.
if the oil pan is removed, will i be able to see the tip of the IMS?
what i'm trying to understand, is if in a case of the IMS going of center, will i be able to re center it thru the oil sump.

[shadrach74]

Originally Posted by JFP in PA

Because the rear IMS sprocket is a press fit on the shaft, and can be dislodged with the set screws (a situation that cannot be corrected without taking the engine apart), I am not a big fan of the set screw method.

When the engine is locked at TDC, and the cams are locked off with the proper tool(s), nothing can move. With the tensioners removed, replacing the IMS bearing is straight forward, and without risk.

Got it. I agree with you. Though I cannot imagine any position that removes all valve spring tension from the cam. Is there a place to get detailed instructions that I might provide to my mechanic?

[shadrach74]

I will have him use LN's instructions though they're kind of austere. I like illustrations, but I think we can make a go of it. There are some confusing sections. see below:

5. Put engine at TDC, and lock out the pulley so the engine cannot turn over.
6. Pull cam plugs and make note of position. It is recommended that the cams are locked out using factory cam timing tool. If two sets of cam tools are available, it is possible to modify the tool to allow both sets of cams to be locked, even with the engine in the car.

If the thing is locked at TDC, why would you make note of cam position?

[JFP in PA]

Because if the engine is locked at TDC, and the notches in the cams are not in the correct positions to accept the locking tool, you already have a timing issue and should not go further until that is corrected..........

[Uller God]

Originally Posted by shadrach74

So I've searched the forums and see conflicting info on my question.

This is my situation. My car is in for service (new clutch, axles, bypass pipes and IMSB). I went to visit my mech and he is in the process fo pulling the IMSB. He has the crank and cam positions marked, but is not locking the the cams at TDC.

According to the Pelican tech article the cams do not get locked.

According to my mechanic, it is impossible to lock the cams at TDC and lock the IMS sprocket because when the the cam and crank are at TDC, the set screw holes are lined up with holes in the IMS sprocket and therefore will not make contact with the sprocket thereby locking it in place.

For those of you that have done this procedure, is the Pelican tech article accurate? Is it the best way to do the IMSB replacement?

My mechanic tore is finger up pretty good loosening the rear tensioners, one was so tight that he needed a breaker bar and when it finally let go, his wrench slipped and he ended up with 5 stitches in his right ring finger. Now one of his shop mates will be continuing the job and I am nervous about the direction this is going.

Any feed back on locking vs not locking the cams would be appreciated.!

Thanks!

Yikes, a costumer informing the shop on how the procedure should be handled?!?!? Has this shop done this procedure before?

[JFP in PA]

Originally Posted by Meir

with that said, why Wayne came up with the screw locking method of the IMS ?
am i missing something in his great article?
and if i got JFP on the hook , i whould like to ask another question please.
if the oil pan is removed, will i be able to see the tip of the IMS?
what i'm trying to understand, is if in a case of the IMS going of center, will i be able to re center it thru the oil sump.

I can only speculate that Wayne was trying to extend his "low cost alternative" to the required tooling as well.

If you look up with the sump cover removed, you will not be able to see very much as the sump air oil separators (arrows) and oil pick up are in the way, plus there is no real access to the IMS shaft because the sump is crosswise to the axis of the IMS and crank:

[JFP in PA]

Originally Posted by shadrach74

Got it. I agree with you. Though I cannot imagine any position that removes all valve spring tension from the cam. Is there a place to get detailed instructions that I might provide to my mechanic?

TDC is the one spot in the rotation cycle where the cam followers (read lifters) are all on the heel side of the cam lobes, hence the reduction in valve spring pressures.

LN has published their written instructions, which while lacking color photos and the like, are more than enough for an experienced Porsche wrench to follow.

[shadrach74]

Originally Posted by Uller God

Yikes, a costumer informing the shop on how the procedure should be handled?!?!? Has this shop done this procedure before?

Yes, I am informing, or I should say having an open discussion about the process. The only reason I have an MX doing this for me is because of time economy. I am very busy at work these days and simply do not have the time or space for a job of this scope. I have rebuilt a number of engines over the years but all were either motorcycle or aircraft engines. My MX has rebuilt a number of flat sixes of both air and water cooled varieties. He has not done an IMS retrofit. In fact both of the indie Porsche shops that I know and trust have never done an IMS retrofit, nor have they ever seen a failed IMS. I know we all get the impression that these engines are blowing up everywhere, but I think it's much more rare than it seems to us. If I were in a major metro area, than perhaps I might have easily found an IMSB experienced shop.

Having worked on Porsche cars before, I'm sure he is very familiar with Pelican and likely used their procedure because it appeared to be detailed and well thought out. I only asked him about it because of what I've read here.

[shadrach74]

Originally Posted by JFP in PA

Because if the engine is locked at TDC, and the notches in the cams are not in the correct positions to accept the locking tool, you already have a timing issue and should not go further until that is corrected..........

Clearly, but they could have just said that instead of "note cam position", which makes it sound as if you're supposed to take a notation of the position of the cams for later use. Neither set of instruction are that well written from a technical writing standpoint, but as I said we'll do fine with the LN instructions.