Engine rebuild timing opinions

Hi all - long time 997 owner but recently purchased a new to me 996 c4s! Super excited because I love the classic look and feel of this car along with the turbo parts it comes with. The car is in excellent condition and was cared for by an enthusiast who daily drove it. It now has 173,000 miles. Car doesn�t smoke at all. Runs and drives and previous owner also showed me some pics he took a few years ago of the cylinders that showed no bore scoping and clean cylinders (see attached). I did buy the car with the full understanding that this will probably require a rebuild sometime in the near future. That being said, wanted to get everyone�s thoughts on timing of this ? Should I just bite the bullet and do the rebuild now or given that it doesn�t have any bad symptoms of an unhealthy engine, can I keep driving it and enjoying it ? I know this will have to be done some time in the near future but just wanted to understand the timing of it. Is it in theory cheaper to do it now or same as doing it later when engine has worn more and showing symptoms of a rebuild ? Thanks again and excited to be part of the 996 community!

Welcome! I love my C4S and 3.6 --> 4.0 rebuild. Mine had bore scoring in cylinders 4 and 6 and at 119k i pulled it and did the rebuild myself. It was such a rewarding experience. There are now over 30k miles on the rebuild. I learned SOOO much about these engines and cars through the process. This forum is such a fantastic resource as there loads of folks here that have tons of experience with these cars. That said, I would scope the cylinders again. To my eyes, image 5 of 11 that you shared sure looks like bore scoring. But, I could be wrong, as my wife often reminds me.

The main reason for doing it now would be inflation� ie, everything is getting more expensive all the time! Other than inflation (or if you just want a more powerful/better/bulletproof engine all around) there is no good reason to �do it now�� Drive the car and enjoy it, maintain it properly� Who knows maybe you�ll get another 100k out of it without an engine rebuild

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^^^ this is my thoughts/feelings also... We see this question a LOT, ......but what I would like to know ( that never gets asked or mentioned) is what is it that people thinks is wearing out ?....... Yes we are all aware of the "early failure points" ...........but if those are addressed or managed, then what do people really think is wearing out ???? I'm not a mind reader, but potentially the engine could last "forever" (or least 1mil miles)....... Aside from engines being over-stressed ( Racing) I've seen engines run for 40-50-60 years and still be run strong and only dye from "neglect" ...lol...

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haha great point. To be honest it might just be a lot of hype and drama that we read on the forums. I�m not technical enough to answer your question but my idea was mainly a cost benefit analysis without inflation. Ie is there any cost savings to rebuilding an engine that still in working condition and has parts that can be reused or when you�re rebuilding the engine you�re gonna end up spending the same amount on the new parts regardless. I think I had read a Jake raby post one time where the cost of the rebuild was dependent on how bad the catastrophic engine failure was� so was contemplating where I wait for the inevitable and keep driving and managing conditions or do it now and save a few grand.

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Yep, thats what I thought ... Here, let me check my Crystal Ball, yep, you will save $6k if you go ahead and spend $35k now on a Re-build.....

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You just got the car. Drive it for awhile to see if you even would like to keep it long term. No need to drop $35-40k in an engine rebuild on a car you probably bought for an equal or lesser value. If the engine blows up or you start seeing a ton of bore scoring, you can decide if you want to rebuild the engine. If you keep your money parked in the market instead of spending it all now, you'll probably make back that few thousand from inflation or increased rebuild costs from a "catastrophic" failure. Best case and most likely scenario, your car will be fine and won't require a rebuild for a long time as long as the known issues have been sorted out and you stay on top of replacing the oil and water pump.

This cylinder is done: Is it burning oil? If that is a yes, then I would rebuild it now IF 1) I have the money, and 2) I want to keep this car long term.

I have a similar conundrum at 194k miles, similarly a recently acquired car as well. Runs well but I found a lot of bits from the timing guides and actuators in the pan. No scoring issues. The timing service will be painful but it�s much much less than any proper rebuild (timing bits will be 10-30% of the cost I think depending who does what work). I�m leaning towards the sentiment above, keeping my savings whole and just doing the required re&re unless I find anything more to indicate otherwise. I am planning to track the car - the biggest liability is in the cockpit, not under the hood. If you feel the car is lacking and are looking to upgrade that might be something else, but if you are just looking for peace of mind, 173k miles and no red flags suggests the status quo is working just fine.

I am sorry, who told you there was no bore-scoring with your engine? The second picture you showed is this.. It is going to look like this once you open it up.

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Agree ^^^ looks like bore-scoring. I may be wrong, some say (Jake? Brandon?) the little camera makes it look worse than it is when you tear it apart. If you have catastrophic failure, the engine is damaged beyond repair or at a much higher expensive process. A 996 engine with 177k miles is "great", but also "iffy". Things around the engine wear out, like engine mounts, trans mounts, coolant tanks, exhaust, cats, etc, etc. The "while you are in there" issues" can really add up $. In the last 3-4 months I have noticed that the top-tier engine builders have raised their prices, and will probably continue to do so, given our current "import policies". Long ago I read that German car makers were required to "maintain or have available" parts for car models for 10 years after ceased production. Meaning you could get parts. 10 years is long gone. Sure, there are a lot of aftermarket 996 parts out there, of different quality levels. But still. parts prices keep going up. Even with a "Pro-Active Rebuild", meaning the car was fine, did OK, lot of miles, no "real giant issues", some of the internals will fail testing to determine if they remain in spec. Do you rebuild to stock 3.6L or go larger? More $$$. How about con-rods not good, or worse, one breaks in some form or other About $3k for new set, less if you use previous owned ones. If broken, what else is damaged? The list goes on... The decision is whether or not you really "like-love" this car. Good news, it is a C4S, only about 24,000 made, so somewhat rare and (possibly) more valuable. Only about 1/2 of the 24k were coupes, rest Cabs. Other "more desirable" 996s were the 40 AE, 911 Edition, any GT3 variant, and 996TT (a little different). Maybe value goes up? Does it matter? For me, not especially. I think any C4S is special and just beautiful with that back end. If you decide this C4S is a "forever" car, or something close to that, then it is worth it to do a Pro-Active build, my opinion. Wait more, price goes up. Is a "more" reliable or new warranty engine worth it for you? If reliability is a priority, then a rebuild makes sense. Whatever you decide, it is your decision. I have not read or heard a single negative review on the top-tier engine rebuilds. However, the process is something a bit different. YMMV

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Appreciate the insight and this is exactly what I was thinking. I admittedly don't know enough about engine internal components so the details here are exactly what i was thinking (i.e.if i keep driving and the con-rods break, i'll be putting an additional 3k during the rebuild process). I also did end up doing some research and found out that the LN engineering retrofit for the IMS was used. It was done in 2013 and at 142k. So it only really has 31k on the new retrofit kit but i was told on the website that if the retro fit kit was used and NOT the IMS solution, it only lasts 6 years 50k miles (im already way over due given that it's now 2026). Would be good to get everyone's opinions on this or is it just a marketing. Now, IF that is true and I have to do the IMS again anyways and drop the transmission, I'm half way there and might as well drop the engine too. I do want to keep the car forever. It's a beautiful color and the rear end of the car will become more of a classic and many have started to appreciate it even more already. Mainly just wanted to see how much longer I could prolong the inevitable. I do want to drive the car since I literally just got it...instead of having to think about a full revamp on the car. With regards to the bore scoring - I also admittedly did not know much about it until i got this car and started at looking at pics. I always knew what it is but was hard to tell by the pics. Im sure there a ton of info on this but that does that cylinder mean i have to do the rebuild asap? PO wasn't shady about any of this stuff and did say that he is selling with the intention that the new buyer will have to do a rebuild down the road.

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Well, if worst case did happen like you say, if a rod busted off and jammed up the works,,, you're looking at a lot more than $3K. You'll be replacing most all main reciprocating parts, like the $6000 crank/etc,, might even have a damaged crank carrier and block. But if engine sounds good now, you have good oil pressure at idle and at speed with no or just a little oil pressure instability, you're probably far away from a busted rod/crank/etc. What did your old oil analysis say..? Why do you think you need a rebuild now...? Does car drive good with no bad engine noises..? On the other hand, if this car is going to be a "forever car" like u said above, and you got the cash now, then might as well get it over with now and enjoy the beefed up much more reliable powerful engine with a warranty. If you use (as You should) 1 of the 2 biggest m96 builders on this forum Slakker/HarTech, or LN (those 2 may be biggest best in the world) u can enjoy a big bore 4.1L with bullet proof cylinders/pistons and most of the engine weak points addressed with a big bump in power... 1 of these builders is a turn key operation. Drop off the car and pick up a new and much improved powerhouse m996 thats been dyno'd and broken in. jmho

Yes, so you are way past deadline for either a new IMS retrofit or upgrade to the IMS Solution. As you know this means the transmission has to come out and you are looking at 10 or more hours of labor so your question is, should I have the engine dropped and rebuild it at this point since I'm looking at 10+ hours of labor anyway, why do it twice? From a financial perspective, you may as well take the engine out and rebuild it and have it all taken care of at the same time. You seem to have several nice cars, so you won't be without something nice to drive. Labor and material costs just keep going up so if you can swing it, do it all now. The next question is "what else should I do?" while the engine is out and for that list: Ultimate AOS 9ii “The Antidote” Fit and Forget Porsche 996/997 Oil Filler Tube 997 Oil cooler Inspect and replace any of the 32 hoses Radiator expansion tank and lid Heat shields fuel injectors not from China 997 swirl pots 997 coils Oil pressure sending unit crankshaft sensor 997 updated oil pressure relief valve Composite impeller Water pump and low temp thermostat Starter/Alternator cable Secondary air check valve That's a partial of my own list of things I've done. Lots more don't require an engine out.

hahah unfortunately those other cars aren't mine. I wish they were but those were in the garage from the PO that i purchased the car from. He has an unbelievable collection and daily drove this 996. Does anyone have any thoughts on this. I got it from another forum. Is it actually needed to do a FULL rebuild like engine builders want you to?? I know nothing about engine rebuilding but did purchase the jake raby dvds and thinking this might be what i need to get started or learn: " One has to consider whether fixing an engine which in most cases is No6 maybe no 5 and possibly no4 is justified by rebuilding to an 'as new' spec when all that is needed is possibly a single cylinder replacing. It is unlikely a 'specialist' would offer or take on this proposition. Consider then a perfectly functioning engine which develops bore score symptoms, if the engine works then why fix parts that do not need fixing? This is the stated position of a new forum member who posted a succinct and educational video of his 996 engine rebuild. Consider also the use to which the completed engine will be put; General driving of a few K miles per year maybe, and realistically how long do you see yourself keeping the car, a year , 2 years forever.... Therefore is an engine rebuild a good use of your capital. It is all too easy to be sucked into the 'engine builders' mantra which is either 'while we are in there we should.....' or as was stated to me ' we will only rebuild the engine if the additional work is carried out' the latter regardless of my opinion of what I considered needed doing based on more years building engines for pleaseure than the the person i was talking to. Hence a bill for 25K: Someone is having a laugh. Or covering all eventualities for a warrenty more like. My final observation is that the 996.2/997.1 vehicle has a market price. There is a clear and defined value range for theses cars, and my research has confirmed that getting a 3rd party to rebuild one of these engines is not an economic proposition, in fact it verges on financial madness. So if you have spent a fair whack on buying the car only to find it has bore scoring what should you do. In my opinion and based solely on the cost of the rebuild is to sell the car, and put the cost of the engine rebuild plus the return on the vehicle sale into either a better version of the car or a different brand. That is why I am rebuilding my own engine and will replace everything that is worn or consumable both internally and externally with an estimated cost including 6 x wetwood liners and Mahle pistons in the region of �6k (give or take)."

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One top-tier rebuilder that offer warranty is Slakker. They build extremely high value engines, and break it in before you get it. It is "good to go" right out of the box. Go look at what their "Basic Build Sheet" replaces and does. It is a LOT of stuff. There may be "surprises", like bent rods, failed injectors, W/P and so on. Some of those items are included in rebuild, others are not. Depending upon what state you are in, the SAI can be eliminated entirely. Quote conversation with Brandon Clark- "It's simple, take it off, plug a few holes, done." If you are rebuilding to make more "$ investment", probably a failure. Invest in real estate or something else, cars just don't do it. I f someone chooses to rebuild their engine at their own level, less cost = less results, whatever, your choice. The "key" is you still decide to rebuild a 996 engine. I guess the 996 is not so bad as to go buy a different brand. The "while you are in there" list can be long, or just what you approve to do. AFAIK, Slakker does not refuse to build an engine because you don't want a particular item, they just do what is on their list. I think if you "opt-out" of something, they will abide from your decision, but possible cancel a warranty - your choice. Some thing mentioned by others are NOT on the list, so they can be considered "extra". Choices again = more $$, plain and simple. Whatever, your choice. Rebuild, don't rebuild. Wait for catastrophe or rebuild Pro-Active before it (really) breaks, your decision.

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For sure, all Porsches will need a rebuilt. Just the way it works. The first thing I would do is level set on the condition of your engine to see how much time you may have. 1. Test your oil to see what it says. 2. Drop your sump to see whats in it 3. Cut open your oil filter to see whats in it 4. Scope your bores to see what you have. in the meantime, I would go thru the Rennvision library of videos on borescoring to understand what you can do to prolong cylinder life so you have some time to figure out what you want in a rebuild and who you want to use to do the rebuild. If the car is a keeper, then do the rebuild right from the beginning. This is your change to upgrade all the parts as well as upgrade the power output. Last thing you want is to regret not doing something when you had the chance. Good luck on your journey. The 996 is worth it.