3.4 to 3.6 swap?

[johnmh]

I have my first 996, a 2001 manual US spec cabrio. Car has 78,000 miles on it and needs a big service.  I am in the process of performing an engine out service on it to change the AOS, clutch, IMS, RMS and to generally just check it out. Interesting engine. I am a long term Italian car guy and am still learning about 996s. 

 

While it will likely fit, does a 3.4 to 3.6 engine swap require an ECU swap as well? Anything else? I have to assume that many others with bad or worn out 3.4 engines have done this (I understand good, used 3.6 engines are more plentiful). 

[judgejon]

Yes, I think it would require an ECU or ECM change.  I would also be careful to check the impact on the remaining drivetrain, clutch, trans, brakes, etc., based on the higher torque from the 3.4 to a 3.6.  Maybe not, but certainly worth checking.  I learned about this with an older air cooled 3.0 engine when I thought about bolting on 3.2 pistons.  Of course that was an air cooled engine and maybe the 3.4 to 3.6 changeover would be less impacting.  And I agree that many others might have considered doing what you are thinking about.  It will be interesting to follow this thread.  Good luck.

[JFP in PA]

There are several "depends" here; what year is each engine as some were different DME version. There is also the question of VarioCam vs. VarioCam+, and the fact that the later engine's were more heavily dependent upon CAN bus for sensor communications.  Any combination is possible, it is just the amount of work required to make it happen......

[johnmh]

Thanks for the information; the variocam issue was  not one I thought of.  Another 3.4 would be preferable should I need to go down that route.

 

On the issue of variocam, I note that the cam chain buffers wear over time and was going to pull the cam covers to inspect mine.  Can the buffers be replaced with the cams still in the head, or must everything come off to do it?  It seems like a bit of a pain on a 5 chain engine. I searched the forum but did not come across any article on the job.

[JFP in PA]

Any time you remove the cam covers, you are going to need cam retaining tools or risk breaking the cams as the cover is half of the cam bearing saddles, and the spring pressure will try to flex the cams which are cast iron.

 

By "chain buffers" I assume you are referring to the chain wear pads, which is probably why you didn't find much when you searched.  On the five chain engines, the small pads between the cams are usually the worst offenders, but can be changes once you secure the cams and remove the cover.  Do another search, this has been covered multiple times.

[johnmh]

Thanks.  Any suggestions for a good source for cam retaining tools?  I managed to successfully remove my double row IMS this morning (it looks to be in excellent shape) so I am slowly gaining confidence with the 996 motor.  I have the cam locking tools in place which are part of the LN IMS kit. I suspect these locking tools alone will not secure the cams to avoid the risk of breakage.  The idea of a cam being so fragile that the valve springs can break it seems odd. I will search for posts re chain wear pad replacement.

[JFP in PA]

13 minutes ago, johnmh said:

Thanks.  Any suggestions for a good source for cam retaining tools?  I managed to successfully remove my double rowIMS this morning (it looks to be in excellent shape) so I am slowly gaining confidence with the 996 motor.  I have the cam locking tools in place which are part of the LN IMS kit. I suspect these locking tools alone will not secure the cams to avoid the risk of breakage.  The idea of a cam being so fragile that the valve springs can break it seems odd. I will search for posts re chain wear pad replacement.

 

The cams are cast iron, which does not like to flex; the valve springs exert several hundred pounds of force onto the cam lobes, so breakage is a real issue.

 

Both Porsche and several aftermarket firms make the cam holding tools, so again, search is your friend, just be sure the one you select matches your year engine:

 

[dporto]

JFP- I hope this isn't a hijack of the thread (I don't think so, since it's related). So, to change out the cam chain tensioner pads, you have to actually remove the cams...In order to remove the cams, they can't be locked down... I find this to be a bit of a conundrum. Which is it lock them down or not? I've seen a couple you-tube videos and the cams clearly can't be locked down in order to remove them. Do you use the end lock tools to hold them down until the covers are removed and then remove the tool? Thanks in advance

Edited June 2, 2017 by dporto

[JFP in PA]

The cams do not have to come out, but the do need to be held in place to prevent them snapping from the valve spring loads when the cam cover is removed.  People seem to forget that the valve springs are pushing UP on the cams, which being cast iron, do not flex, but do snap in two if not correctly supported using the end plates and saddles shown in the kit above.  He is the cover being removed with the end retaining plate in place, but before the extra saddles are added to even out the spring load:

 

 

And here you can see the cams retained, this time with home brew saddles made from bar stock:

 

[dporto]

I get that, but how do you change the Vario-cam pads without taking the cams and tensioners out? And, how do you take them out safely without breaking them. I keep going back and forth on this - there seems to be conflicting advice? - Thanks

[JFP in PA]

36 minutes ago, dporto said:

I get that, but how do you change the Vario-cam pads without taking the cams and tensioners out? And, how do you take them out safely without breaking them. I keep going back and forth on this - there seems to be conflicting advice? - Thanks

Once secured, you can remove the VarioCam unit, undo the chains, and replace the pads between the cams, or if you choose, remove the cams entirely.  

 

 

 

However, if you are changing the larger lower chain wear pads further down on the chains, removing the cams does make that easier; but then the engine would also be out as well.

 

[JFP in PA]

The more I think about this, if you are a "first timer" doing this, it probably is going to be easier for you to pull the cams and do it on the bench, then reinstall the cams.

[dporto]

JFP - Thanks for all the help!!! Yup, first timer here. It seems to be a little simpler by pulling the cams, though if it's "safer" yet more difficult to do them while they're in, I would probably opt for the difficulty. My question is, do I lock them down to remove the cam cover and then remove the lock downs (the cam end holders) ? Or, do I just not lock them down at all? Also, remove the 3 chain tensioners correct? They're already out, as I just finished installing a new IMS bearing (LN IMS Solution) so I would not be putting them back to do the variocam chain rails?. 

[JFP in PA]

12 minutes ago, dporto said:

JFP - Thanks for all the help!!! Yup, first timer here. It seems to be a little simpler by pulling the cams, though if it's "safer" yet more difficult to do them while they're in, I would probably opt for the difficulty. My question is, do I lock them down to remove the cam cover and then remove the lock downs (the cam end holders) ? Or, do I just not lock them down at all? Also, remove the 3 chain tensioners correct? They're already out, as I just finished installing a new IMS bearing (LN IMS Solution) so I would not be putting them back to do the variocam chain rails?. 

 

You cannot lock the cam positions while doing this, but you must lock the engine at TDC at the crank pulley.  Regardless of if the cams are being pulled, or just disconnected, you are going to need to retime them once all the updates are completed, which is why you don't lock them, they are going to be out of time in any case.

 

The cam retaining plates are inserted through the green plug openings before removing the cam cover, as seen in one of the photos above.  You need to also remove all four chain tensioners, which includes the one underneath the AC compressor.

 

I would also seriously consider pulling the cams as you do not have the tools we had fabricated to compress and hold the actuator to get the small pads out.  Again, you are going to be retiming the engine anyway, so make your life easier.  Also pay attention to the pads themselves, two have small holes in them, two do not.  They are not interchangeable.

[dporto]

I actually do have the "bicycle skewer" tool to compress the tensioner. Also, the one on bank 1 is regular right handed thread - lucky I guess. I got the cam cover off tonight. It's quite a messy sealant job so it'll probably take me a fair amount of time to get it cleaned up.

[johnmh]

Thanks, that gives the answer I was looking for as well. Tools have been ordered. Now if only I could decide between the LN IMS Solution with external oil feed ($1700) or just the ceramic bearing ($700).  Probably covered elsewhere.

 

[johnmh]

On a related note, do you typically also replace the lower (inner) variocam chain rails at the same time? All the pics I see are of worn upper rails (which makes sense as they do all the work). These should have a different part number but I have been unable to find them.

[dporto]

Hi John,

              You're probably talking to JFP, but I'll interject anyway (since I already hijacked your thread...). FWIW, I decided on "The Solution" because I plan on keeping the car. Even with this decision I was a bit torn, as who knows whether I'll actually get more than another 75,000 mi. out of it (that's what the ceramic bearing is supposedly good for). I figured it was worth the "do it once and forget about it" factor - it's only $... In looking at the upper vario-cam pad last night it didn't look badly worn at all. I'm hoping the bottom one is worse, and that's what gave me the out of range deviation... From what I can see of the other chain rails (the large black ones - IMS and main chains) they don't look worn either. Clearly the black debris in my oil screen was sealant...

[johnmh]

Thanks, I will probably get the IMS solution as well.  I was looking for a new project car and was offered this running manual '01 Cabrio for next to nothing.  While pulling it apart has been interesting, I do not want to do it again any time soon so I am chasing things that are more preventative at this point.  Once the IMS solution is in, and the variocam pads changed, I begin the process of putting it all back together and seeing if I remember how it goes back into the car.

[dporto]

^Exactly my thought process^! I just got the bank 1 cam cover off last night and will start into the vario-cam pads tomorrow...Good luck with the project 

[johnmh]

Thanks, same for you. I assume you are putting the cams on the bench with the solenoid unit when you do it.  Please advise if it was easy or difficult.   Specifically, were the painted links on the chain between the cams lined up with the dots on the cam sprockets as it shows in the manual?  

 

Are you replacing the solenoids too?  After 16 years it might be time on my car, but I can neither bench test them nor see if they were replaced.  No service records came with the car. 

 

[johnmh]

A quick question, the engine is on the bench but with the exhaust still connected to it (no desire to helicoil all the exhaust / head manifold bolts).

 

Can I leave the exhaust in place, but simply loosen the muffler brackets in order to remove the cam covers? I can get to all the 10mm bolts which hold the cam covers in place but have no idea if I can slide the covers out from under the (unattached) brackets.

 

For neither love nor money can I figure out how to remove the brackets with the mufflers still connected to the car and the shiny new cam locking tools will arrive on Monday. 

 

 

 

[dporto]

Yeah, the exhaust system is like a puzzle due to the way the pipes cross over. It's possible that if you take the rear engine support bracket off (the one that hangs on the engine mounts) you may then be able to remove the mufflers and cat pipes in one piece. I'd say it's a long shot though. Just as a note, on my engine the bolts from the headers to the heads all came out easily - none broke, and none of the heads stripped either... Good luck

Edited June 10, 2017 by dporto

[johnmh]

I cleaned the threads on the horizontal clamp bolts with a die, heated the bolts and then lubricated them.  Happily all four came loose without issue.  Thanks!

 

[dporto]

I wasn't so lucky with the rest of my exhaust hardware... a bit a of a nightmare actually... lots of cutting and breaking of old/rusted bolts!