996 Lifter replacement questions

I'm hoping some folks that have done this before can help me with some questions. I have a '04 996 C4S with 103K miles in superb condition. My engine is a 996/03. The IMS and RMS, AOS replaced, sparks, plugs all done around 78K and the car just runs great. What is absolutely driving me crazy though is a tapping sound at idle after the engine has warmed up. This comes from the passenger side of the engine. After a lot of research I'm fairly certain it's one or more stuck lifters. I've worked on engines before and want to do the replacement myself, but have some questions: 1. Are the exhaust and intake lifters the same or are they different? I have this part #: Porsche: 996 105 041 72 (and alternate BMW: 11 32 1 748 884) Can someone confirm that those are the correct lifters for both intake and exhaust? 2. To get the lifters out the cams need removing. Will I need to adjust the timing when I put them back in? The guide on Pelican says I can just line up the timing marks on the chain and gears, but I'm not sure about it. 3. I'm considering doing this without removing the engine. I know it would be easier with the engine out but I don't really have the room to do that and although I'm sure it will be a bit cramped, it looks possible. I'm thinking the biggest pain in the *** will be when I break the header bolts removing the exhaust and I'll have to buy a stomski tool to address that. Any comments on doing on on-chassis lifter replacement? Thanks in advance!

Does it sound like this? The intake and exhaust lifters are different. The intake lifters are much more expensive. You Tube

It does sound very similar to that but it's difficult to differentiate that sound from noisy lifters. I forgot to mention that I brought it to my porsche mechanic and he told me it was definitely not cylinder slap, and was very likely a stuck lifter.

The "porsche mechanic " who did the ppi on my car said it wasn't piston slap either. "No way the cylinders are scored, try a different oil" My cylinder 4 & 6 were completely scored. post a video of your car idling here. People have done lifters to only start that car back up and realized it wasn't the problem at all. Hate to see you waste that money and effort.

The video teaches you how to tell this sound is from the cylinders. You just need someone doing the same to confirm. The intake and exhaust valves are #5&6 here http://www.autoatlanta.com/porsche-p...section=103-11

What if you didn't replace the stuck lifter? What are the consequences?

Quotes source post: 14760355

Being a Porsche mechanic also, I feel the need to take up for the trade a little bit. These M96 engines suffer from bore scoring more than any engine type I have ever seen in my 40 years of being a mechanic. And the symptoms are not typical of other engines that have bore scoring. Any mechanic who does not know how unique and widespread this problem is will find it hard to believe. I remember back about 15 years ago while attending Porsche special training class W10 ( water-cooled engines), the Porsche instructor mentioning that the pistons of the m96 had an offset piston pin that helped reduce side loading after combustion on bank 1, but unfortunately they they used the same piston on bank 2 which would increase side loading. I haven't actually measured the pistons to see which variations of m96 had this off-set or if they all have this off-set, but obviously (if true) is a cause of bore scoring that could not be fixed, since there is no other option for factory pistons.

Thanks for the replies. I'll wait until the spring when I take the car back out of my garage and will get a second opinion at the dealer or other Porsche expert shop.

Quotes source post: 14760995

Really ??

Quotes source post: 14761766

Yes, really. The only engine type I can think of that comes close is the Chevy Vega 140 of the early 70's.

Interesting. I guess the issues with hot spots and cooling are a factor & oil change intervals etc.

Quotes source post: 14762699

They are, the hot spots, cylinder cooling, oil quality, and piston pin offset on bank 2 are all contributing factors.

Quotes source post: 14760995

Yes, 0.5mm offset on my '02 996 engine. See post #564 here https://rennlist.com/forums/996-foru...l#post13253105

Quotes source post: 14759874

The intake and exhaust lifters are different. Exhaust https://www.warehouse33auto.com/INA/...996-105-041-72 Intake https://www.warehouse33auto.com/GENU...996-105-255-25 -Jason

Quotes source posts: 14763412, 13253105

Thanks Ahsai, I actually had thought the piston pin offset hadn't been discussed in Rennlist forums, I should have know it would have been discussed in your detailed engine build thread ! So it looks like the offset pin was in the ALL m96 and m97 engines, when I first heard about it, the m97 hadn't even been produced, shame.

Quotes source post: 14763844

I simply don't understand why Porsche put the offset for bank 1 into Bank 2 - why did they not have an opposite one for that side?

Because the valve pockets are different between the intake and exhaust. The only way to have a correct offset would be to make two different pistons for each car. If you get an offset aftermarket piston with equally sized valve pockets, then the orientation arrow will be correct for both banks. This is a known problem with other Porsche models also.

Quotes source post: 14773422

The simple answer is that it would cost more to make another piston to fit bank 2 correctly. I'm sure the decision was made by the accounting dept. and not the engineering dept.

So I finally managed to get some time to take a look at with an endoscope and concluded that this is due to cylinder scoring (Cylnder #6 video below). Cylinder 6 scoring - endoscope Sooooooooo....after some crying I've decided to rebuild the engine. I'm an engineer and am comfortable taking this on, and I'm lucky to treat this as a project and not fixing my daily driver - although it will be my daily when I'm done. I'm also hoping that a few on this forum that have done this before are generous in their advice and sharing knowledge if/when asked. I have read the posts from Ahsai, Logray, redneck rebuild, and a few others at least three times and will re-read them again (and again probably). I can't start this until the springtime anyways so I have a little while to prep and research it. I would love to take the Flat6 hands-on rebuild course but unfortunately that is beyond my budget. The online courses look interesting, and I do plan on taking one of those, but still trying to figure out which one I should take. At this point I'm not sure if I should get the full LN Kit ( https://lnengineering.com/products/w...ins-clips.html ) or send it out for repair, for example to Millenium Technologies ( http://www.millennium-tech.net/serviceInfo.php?id=7 ) and buy the JE Pistons, etc. There looks to be a significant cost difference between the two. I don't plan on tracking my car, and obviously want to keep costs down as much as possible, but also want to do this right, so any thoughts on options appreciated. I'm hoping to give back and be able to document all this but will depend largely on my schedule.

By the way, for anyone that want to look at their cylinders, you can get a really affordable ($37) endoscope here: Amazon Amazon Then just pull your plugs and take a peek. (Make sure someone is nearby in case you need a hug)

Sorry to hear that man. Thanks for sharing the great video. I use the exact endoscope btw. Excellent video quality. ​​​​​​ Regarding the cylinder repair, I would highly recommend going with LN because they have figured out a package (combination) that works well. Their JE pistons are also custom made. Not to mention their expert experience and how great Charles and their staff are. They just go beyond in customer service. Also definitely go with a 3.8 or even 4.0 Jake's class will guarantee the knowledge you need to be successful on your first try. If you can't attend the hands on class, you will have to do a lot more homework and accept the fact that it may cost you more time, effort and frustration (e.g., redo something if you missed something 50 steps before). Can't wait to see your future update on this rebuild.

That sucks about your cylinder scoring. Great clarity from your borescope, thanks for sharing.

One more thing. Are you sure the price you got from Millenium includes the new billet aluminum cylinders themselves? The NSC plating is just the plating and honing part. The LN nickies process includes removing the whole cylinder down to the deep part of the engine case. That removes most of the parent material before inserting the stepped nickies cylinder. http://support.lnengineering.com/201...er-cayman-911/ I think even iron sleeves are like $500 per cylinder.

Thanks, I'm interested in going to the 3.8 or even 4.0, but only if there aren't cascading costs for other things that would need upgrading, like the cams, chains, etc. Any idea if that is the case? I wouldn't go the iron sleeves route - doesn't seem right to me.

My understanding is the 4.0 will require new rods. Other than that, most of the stock components such as cams and intake lifters can be reused on both a 3.8 and 4.0 builds.

Quotes source post: 14775292

Typically I will advise that if going larger than a 99mm bore, that the rods be upgraded, due to the increased piston mass. That said, plenty of people have just put ARP bolts on the stock rods. If you never will autocross or track the car, you'll be fine. If you change your mind or someone later on tracks the car, that's a different story. I've seen too many stock rods break at the beams on track to not advise replacing them for that purpose We are working on a cheaper option through JE's sister company, K1, but we are still quite some time off from those rods being tested and ready. Goal is to be well under $1k so that we have a price point for a quality rod to our specs that are less money than a Carrillo.

After thinking some more on this I'm concerned with putting the higher combustion loads on the existing head and crank. I will have my heads pressure checked but even if I stay with the 99mm bore (3.6L) should I be concerned about this? Remember, daily driver, not destined for the track.

Quotes source post: 14779031

The stock bore size on a 3.6 is 96mm. When sleeving the block, 99mm Nickies take the displacement to 3.8 liters. This is the same bore size as a stock 3.8. That's why we say that's the limit for street with the stock 3.8 rod, as we don't want to go bigger (heavier) than the original pistons. Even at 96mm, I would recommend installing a set of ARP rod bolts. Cheap insurance. Don't be concerned about load on the heads or crankshaft, even with increased displacement. That's a non-issue. Just make sure you have both properly checked by experts familiar with the M96 engine. Lastly, make sure to put a new dual mass flywheel. No single masses with a stock crankshaft. If you use a billet crank, that's a different story :-)

Thanks, given your response I'm back on with the 3.8L displacement and I'll do the ARP bolts. For anyone reading this thread in the Northeast area (North of Boston) - can anyone refer me to a shop around here that has build experience with M96 engines?

That sucks. Sorry to hear the news.

Oh wow never heard this information about the piston offset for the bore scoring issue. Sorry to hear OP. Man all of these threads make me want to sell the car while it is still running ok

Quotes source post: 14774255

This thing is awesome. Thanks for the recommendation.

Quotes source post: 14775292

[Image-only post; no author-written text. Original image references:] https://rennlist.com/forums/images/smilies/frown.gif

Quotes source post: 14779081

Is a billet crank available for the M96 NA engine? Looking at EVOMS & Protomotive, it appears these are for the turbo and GT3. So 3.4 > 3.8 with nickies, billet crank, single mass flywheel is doable? I'll start a new thread if this is going too off-topic.

Quotes source post: 14781705

Billet cranks are indeed available and come with a hefty price tag. Something Jake uses in his builds exclusively.

Charles: Are the JE pistons that are included with the Nickies different for cyls 1-3 vs cyls 4-6 regarding piston pin offset? Thanks in advance.

Quotes source post: 14781843

I'm not the Charles you were looking for , but can answer your question. The JE pistons included with Nickies are zero offset, therefore are ambidextrous.

Quotes source post: 14781899

Spot on. I have done them with offsets special order, and when we do, we make them side specific. The DFI and Cayenne V8 pistons we make must have offsets or the engine sound like diesels.

How is making one side more favorable while the other is left with a unfavorable offset chosen over just non offset pistons for all 6?

Quotes source post: 14782096

Several things are effected when offsetting piston pins. Offsetting piston pins in either direction will soften the "snap" when piston changes direction at TDC and BDC, this reduces the stress on the rods. Offsetting opposite the direction of rotation will decrease the piston slap and reduce side loading of the piston. Offsetting in the direction of rotation will increase slap and side loading, but will slightly increase power and dwell time at TDC, as mentioned above any offset in either direction will reduce "snap" stress on the rods. Ultimately the decision on whether or how much to offset in determined by the engine/piston designer and/or their accountants.

So if an absent minded M96 engine rebuilder muddles the offset for Bank 1 & 2 when reassembling the engine , what happens?

Quotes source post: 14782889

Impossible because all m96 pistons are identical within an engine.

Quotes source post: 14782889

Ahsia is correct, on the factory pistons, you can't mess that up, they are all the same. Ideally like Charles Navarro said, when they do offset them, they offset bank 1 to the exhaust side (major thrust side), and bank 2 to the intake side (major thrust side). Then you have the best of all worlds, offset to reduce piston slap , to reduce side loading, and to soften the "snap" at TDC.But requires two different pistons be made, and close attention to orientation during assembly.

It's just my opinion but I think the engineers of the m96 engine chose to use piston offset for the softening of the "snap"at TDC .And they figured they could get away with using one piston,( even running an unfavorable offset on bank 2) due to the surface of the Lokasil cylinder, the iron piston coating , hypereutectic piston material, and close clearance, would withstand the side loading and piston slap all to a minimum, but as we know , not so much.

So you guys bring up the best info as 996 owners and builders....I've decided to go back to purchasing a 996 after looking for a 997 and it seems the Gen1 ones are getting below the $36k range but with the 996 offering better bang for bucks, but still having issues. Would a PPI catch scorned pistons? Or this something one will have to ask for?

Quotes source post: 14787077

for 36k you can get a decent 997.1 good miles... even in the high 20s and a regular ppi wont unless u pay extra to have car scoped to check walls ..