Mismatching Engine - PCOA

Note: If there is an existing thread, kindly direct me there. I was unable to locate a thread that discussed my use case. Background There is a 2003 996 4s that I am considering to buy however I am moving cautiously after I learned that the new engine was replaced with a new engine in 2006. Old Engine Number M96/0366317286 New Engine Number M96/03AT66565613 The service records indicate that the first engine experienced engine failure and was replace with a new engine. Overall service records look solid as do the car research services records eg. CarFax etc. The seller claims the new engine is a "997" that shouldn't have an IMS bearing issue. This feel dubious based on my research but I did read that the 997 engine was based on the 996. I reached out to the seller to inquire about the authenticity of the new engine and my understanding is that Porsche has no record the engine was swapped. Questions: If the engine was replaced and Porsche doesn't have record, is there a path to have them update the records? Will having a swapped engine without record from Porsche be in issue for a Certificate of Authenticity? I understood that the 997 engine may also have IMS issues, is this true? How should I interpret the new vs the old engine numbers and are there any red flags based on your experience. My goal is to cut through the BS online and consult with folks who are more experienced than myself in this area. Let me know if there is additional information required to help your analysis. Appreciate your time and consideration.

Old Engine Number M96/0366317286 New Engine Number M96/03 A T66565613 Believe that A means factory replacement engine

It's the AT ('Austausch' ie replacement) not the A alone that denotes a factory replacement engine.

Don't know if this would help. The Porsche Classic Technical Certificate seems to be a new program first offered on 2022. Don't know if it deciphers AT engines info but may be worth a phone call to see. https://www.porsche.com/usa/accessor...alcertificate/

For starters, you may even already know this, 996s out there that received new engines relatively early on in their lives is -- I don't want to say common, but certainly not out of the ordinary. That being said, if someone finds a car that checks all the boxes otherwise, an engine (factory replacement) other than the one it was born with shouldn't be a deterrent. That said, in this particular case, I would be cautious regarding which IMS bearing the car currently has. A girlfriend of mine had an '03 996 Targa 6spd. that too had a factory replacement engine that was installed by Porsche in 2006 as well. It was the exact same M96 with the, shall we say, less-than-desirable IMS bearing that was in the engine that had been removed. The question that is a little odd in your case is that Porsche has no record of it being refitted with a replacement engine? How does all of this affect the C of A? No idea, but I wouldn't lose sleep over the C of A. Most Porsches of this vintage the C of As went missing years ago. And even if one happens to still exist, it will still be a cool piece of documentation, new engine or not.

Yeah, m96 engine replacement thru the Porsche factory was pretty common thru 06 due to the use of the "go-no-go" tool during the early RMS failures until they found the right RMS all of which was under warranty. Porsche kept the program in place where any of us back in the day could swap our engines (long block) at the dealer for a new one at a relatively inexpensive price around $7.5k. It was a very good deal so none if us lost any sleep over engine failure. Price then went up to $15k with an exchange and then they eliminated the program but kept the core short block exhange program which you can still find for $8-10k. As these Porsche engine exchange programs evolved, so did the need and opportunity for engine rebuilders who increased output, upgraded cylinders with nickies, added better pistons and internals, etc., producing a more powerful and more durable engine. Can't speak for the 997, but Porsche has offered the same type of engine exchange program for the 991 and 992. Things may have changed over the last 2-3 years, but very few 991 owners rebuild their engines. Instead, they exchange it. Haven't heard much about the 992 since the model is new, but I would suspect they will have a similar program. I wouldn't sweat an AT engine since it was common then and common now for water cooled engines in newer models. The key is if the bores are in good shape and what IMSB you have. Someone will know the answer on if you can replace the 997 IMSB without cracking open the engine. You may want to check on LN Engineerings website and or give them a call.

OP - I can’t find the reference right now, but there is info on the interweb for the serial number break where the M96/03 AT engines were made with the non-replaceable bearing (starting spring ‘05 I believe). You could reach out to LN and see what they know for this subject. The only visual reference would be to pull the cover off and see if the case is milled. So, no bueno there. Any non-Mezger M96/97 engine is susceptible to IMS bearing problems. Don’t get consumed by the mania. Stuff happens and each sports car has its own kryptonite. Find the car that ticks the boxes, continue to gather all the knowledge you can. Buy the seller and service records. A little more research should get you the info you need. I spent 9 months learning about M3s and 996s before I bought my first 996. Good hunting!

Because of bore scoring, IMS, etc., there may come a day when very few 996�s still have their original engine. And the ones that do will know they aren�t long for this world.

Yep. Every engine known to man will eventually need a rebuild. Glad I own a 996. I can only imagine the huge cost involved with rebuilding the modern 991 and 992 engines after Porsche scales back it's engine replacement program. It's not a matter of IF, but WHEN.

It's a 996. I don't believe it will ever matter in the future whether the engine is original or not. Buy it; drive it. Don't let the tiny sometimes hard to read numbers worry you.

My 2000 MY 996.1 has an AT = exchange engine and as was previously stated this was likely due to the Go-NOGO gauge era, which came about because of the oil leaks produced by a poorly sealing RMS, my internet research has led me to believe there was an issue of the Alignment between the transmission and the engine block which prevented an RMS seal form actually making a good long term seal, eventually the exchange engine program kicked off if at a dealer the gauge read NOGO then you got a new engine/block. so onto your prospective car, you going to need to address the IMS no matter what 996 you buy, unless you have some decent service records that show it was done recently by mileage, there is mention of an IMS that can only be replaced by splitting the crankcase, obviously that will be quite expensive, your car could fall within that date range, unless the car is special in some way or especially cheap i would keep looking, there are some cars that are gotta have spec cars, mine would be Aero, LSD, manual, unusual color, a nicely specced interior, no sunroof, very well maintained in most respects, low ish mileage, an early 996.1 with wire throttle. if its a regular old cooking low spec 996 (no offense) keep looking there are some real gems out there.

Not misalignment between engine and transmission but between crank cradle/carrier and the engine casing around it.

Quotes source post: 18819545

This car has the M96.03 996 engine, not the M96.05 found in the 997 and it's definitely not a M97. If this M96.03 replacement engine was manufactured in 2006, then it would have the large single row 6305 IMS bearing. Which is a good thing because it has proven to be the best of all three designs with a very few reports of failure. One point of concern would be if this replacement engine was actually assembled in 2005 or earlier and was delivered and place in storage. That would mean it has the dreaded 6204 small single row bearing which was well-known to be the worst offender of IMS bearing failures. My gut feeling would be that it has the 6305. Questions: If the engine was replaced and Porsche doesn't have record, is there a path to have them update the records? From personal experience, their record keeping is not shared from dealer to dealer. The Porsche dealer that did the install might have record of the service, but many don't go back that far. Will having a swapped engine without record from Porsche be in issue for a Certificate of Authenticity? No. Send them enough cash, and they'll gladly print it on paper milled from the trees of the secret Stuttgart elfen garden. I understood that the 997 engine may also have IMS issues, is this true? The '05 model with the 6204 bearing had as many issues as the 996. But the post 06 cars with the 6305 have very few reports of IMS bearing failure How should I interpret the new vs the old engine numbers and are there any red flags based on your experience . The old engine ate itself and that's all you need to know. They put in another engine that will eat itself too. Modern Porsche love to eat themself to the bore.

Remember when Porsche Issued a recall on all 991.1 GT3 engines and replaced all of them due to loosened screw joints on the connecting rod. Engines caught fire.