Tradeoffs on displacement for a 996 rebuild.

So poking around couldn't find anything that kinda rolled through it,,, 2003 996 C4, 3.6 in good shape,, but has 112K on it. generally well serviced, but thinking ahead, if I were to drive the car to RND to get the engine refreshed. The big step is what all do I do to it. Obviously a shiny set of nickeys.. IMS solution,, Baffle & pan What displacement?? is there a downside to going 3.8 or 4.0? I would assume that if everything else were stock(ish) that a 3.8 bump is likely a no brainer. Goal, I want this motor to LAST. I am not looking for super gee wiz power.. Basically at my age (56) I figure if we rebuild the motor with good parts and its well tuned and freshed,, It should last till I switch to something that doesn't require reflexes or vision.. I wanna be "that" old guy in the Porsche....

What are you looking to use the car for? If just a fun car for use on the public roads, the 3.8L will most likely be the better choice. If you're planning for an elective rebuild, please PM me.

Subscribed as im curious about the answer. Would have thought if you're there go the 4.0? Why not?

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At age 68(69 next month) I went with the 3.8 Street Performer choice from F6I because I don't plan to AutoX or track it. I have a Civic Type R if I get that itch. I also wanted to keep the car "stock appearing" i.e.: stock intake and stock exhaust. Although not sure if a mild 4.0 absolutely requires those changes. At my age I guess I AM that old guy in a Porsche...and loving every minute of it! BTW vision, of some sort is always important in driving regardless of how fast the car is!

Having gone from 3.4 to 3.8 on an elective build, I can only add my 2 cents to your question by saying that the increased torque, drivability and power throughout the rpm range is absolutely intoxicating. I can only imagine that a 4.0 would be even a little bit better ! This is the way the car should have come from the factory. It's also a lot of fun to surprise newer 911's when they can't quite pull away that easily from me.

I'm fairly confident, when it comes to the M96, bigger isn't always better. Seems like the 3.8L displacement is the best configuration before needing to upgrade other supporting parts to maximize the increased displacement. Just isn't worth it to do it right financially.

This is a great question. Hopefully Jake will interject.

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^^ This ^^ I just did the same. I'm planning on doing a comprehensive post of my impressions of the entire experience, but suffice it to say in the meantime, I'm mighty impressed.

Good thoughts,, I was kinda "assuming" that 3.8 not a big deal, 33 CC's per jug. a 4.0 is about 66CC's per jug (Approximately) 3.6 = 600CC cylinder 3.8 = 633CC cylinder 4.0 = 666CC cylinder I have to believe at some point ,, a new Throttle body may be mandatory, in checking the main players that rebuild these engines, I notice a couple of the really top shelf ones don't offer the 4.0 as a standard setup.. they max at 3.7 to 3.8. As much fun as the car is at 3.6 the economical side says don't over do it,, the right foot side says there is no such thing.. LOL

What is the cost difference between the different increased displacements? If it is nominal, I don't see the downside to going as large as the builder recommends... is it an issue of the other systems (transmission, axles, brakes, etc?) that need to be upgraded to handle the increased power?

You know what Enzo would say. There is no replacement for displacement.

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How is that on the track?

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Mostly head work & camshafts.

The LN nickies are the same price for all 3 sizes.. That's what started me thinking.. I've been thinking that if the motor runs out to 150K a proactive refresh might be long term less $$. I just have to decide if I want to do it myself or pay the freight .. Since I'm a west coaster its non trivial to get a car or engine to the right place.

The �bigger is better� mindset doesn�t work. Often people see a bore size and go for the biggest one, just because it may not appear to cost any more... BUT, it does. To feed the larger bore efficiently requires optimized port work, which then leads to other changes, that must then lead to other changes. If you simply throw a bore size change at these engines, efficiency drops really fast.. I can build a 4.3, or even 4.4L engine, but those makes up about 10% of what we build, because they require the most amount of other work to optimize the displacement increase. Even when we developed the very first 4.0, and built the first one with Nickies, I seldom went to that combination. In fact, my most efficient engine, making the most power per cylinder is a 3.7L. It makes more power per liter than my 4.0, until we apply Stage 3 tricks to the 4.0 Building an engine means more than making it bigger. The �bigger is better crowd� has always been the easiest to beat. Why? Because they beat themselves.

Thanks for commenting,,, that's kinda what I was headed, where is the crossover point, in cost+labor+more mods needed to finish.. FWIW,, the 3.7/3.8 is what I have had recommendations from other engine shops as well. Same scenario as the old AC cobra's,, on a tight rod course the 289 cobras would out run the 427's just because they were lighter and nimbler in the turns. All the old time drivers I met preferred the small engine cobra.

See, what plays into this more than anything is something that shouldn�t.. All the time I hear from my purchasers �my friends can�t wait till I get the 4.0 installed in my 996� Too many times people buy things not because it�s what they need, or what they can afford, or what�s the most efficient. They buy things because their friend doesn�t have it. We constantly struggle to keep the decisions of the purchasers to be made wisely. If someone really does �want� the bigger engine, I require them to add the things to it that will help it remain efficient.

THAT OLD GUY.....HA, I'm on my 7th 911 ( and 4 Boxsters, a 914, a couple of 356's etc) and I'm 84 Keep drivin"

In addition to "displacement", I believe the skills of the builder are paramount.! M96/M97 engines are complex and build experience is hugely important, especially in re. long term reliability. Before deciding, visit some builders, talk with the techs, ask for references and then talk to them! At $10-15K a pop, such projects deserve time consuming due diligence, not unlike picking a surgeon for your spouse. relinuca

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It's not how big the engine is built that matters, but how you build it big. I do agree with you, but also find that "experience" without forced discipline, check lists, and quality control can lead to corners being cut. As people build more, they learn how to 'just get by". In a normal shop atmosphere, where there's no quality control checks, and people are not having someone look over their shoulder, the experience can lead to negative things occurring. A good example is a builder assembling an engine against a clock, using the assistance of an impact gun to tighten fasteners. In one of my classes an attendee actually admitted "I can get torques perfect with my impact gun set on #2, and getting 3 chatters on each fastener. It works perfect every time, and saves me hours". As more and more people jump into this game, we see engines with huge cylinders, fitted with steel sleeves, piston ring tensions found in a big block chevy, some IMS Bearing that's sourced from Romania, and they top that all off with stock cylinder heads and stock valve springs that are worn out..They use the displacement too sell the engine, and often they will leverage "The engine is the same size that flat 6 builds, and it's just as good, but less than half the price, and you don't have to wait a year for it". The typical purchaser doesn't know how to grade the engine, and these other guys use that to their advantage. The normal purchaser just knows an engine size, and automatically equates that to the engine being more powerful. We see engines that are built larger than stock, make LESS than factory power all the time- because they were haphazardly built by someone that only is concerned with profit. In other instances the builder simply doesn't know, what he doesn't know, and they truly believe they are doing the best thing, and building a great engine. They usually run an "everything Porsche shop" and therefore they are not just engine builders. In other cases they run a "race shop", and they may know how to do a great corner balance, or alignment, but they have no idea how to tighten a connecting rod bolt using a stretch gauge... Just as an example. These people are engine assemblers, and their workshops lack the tools in house to complete an engine building task without outsourcing 90% off the tasks to sublet shops to do all the critical work. I hear people bitching a lot, and they say "Raby thinks he is the only guy that can build these engines". My reply to that is "The people who say this are often the same ones who laughed at me 15+ years ago when I started tooling up to do this work, and learning about these engines". This is the truth, back then no one was working with the engines, as they could be bought cheaply from the dealer, parts were not easy to buy, and we had to make all our own special tools. What I loved about that period was the pioneering, and the fact that we really had to fight to get a positive result. I knew that what I was doing at the shop everyday had never been done before, and that no one else learned what I did that day. A little bit of foresight, forethought, and a lot of doing, without a lot of talking put us where we are. Everyday has remained a school day, since day #1, when I disassembled the first M96 engine, and had no idea what in the hell I was doing. Here's an actual account from 8 years ago that's worth a read. Today these stories are more prevalent than ever, and we find a solid 1/3 of our work is coming from the failed attempts of others. In most cases we have to throw away all of what the "other guy" has done, and start from scratch. http://flat6innovations.com/spare-pa...-bad-decision/ Sorry for a novel, but I'm at the beach this week, and aside from spending quality time with my daughter, I wish I was at the shop!

We'll be back soon! Annual Summer Shut Down! Just a quick note to let everyone know that we will be closing at the end of the business day of 06/28/19 and will be re-opening on 07/08/19 This is an annual planned event we practice every year in observance of the July 4th Independence Day Holiday. We wish everyone a safe and happy 4th, and look forward to catching back up when we return on the 8th! During this time telephone, and online support will not be available. We will reply to system tickets in the order in which they were received, upon our return on 07/08/19. Our website is under scheduled maintenance. We're working on updating and upgrading the site - we apologize for the inconvenience! We'll be back in: Jake, this is where your link (above) took me...I always enjoy going back and reading your stuff, but it's not there. Enjoy your break!

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Yeah, the webmaster is taking advantage of our shutdown to catch up on site work. It�ll be down till Monday. Lots of what was there is being removed, too.

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Well, with 306 hp, 295 ft#'s of torque, right around 3100#'s, with a capable suspension, tires and Brembo front brakes it is pretty good. Until just recently the Type R had the record at the Nurburgring for street cars front wheel drive at 7:43.08 which is quicker than numerous "fast" cars. Forums say it is a good track car. Even read a report from an instructor who is a Porsche owner(but tracks a Miata-quickly) that is was a fun car on track. I have no experience, yet.

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We'll see what I can do for you :-)

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...and that's exactly why I sent it to you!! NOW pay attention to the beach!

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While on vacation I decided to go see my next patient.. Another engine I am doing for Miles Collier, and the Revs Institute. It's for an early Gmund coupe. It last ran in 1965. Should be a blast. ​​​​​​​

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If you look at a 3.4 as an example, the work to the block and the pistons aren't any more expensive for going to 3.8 than 3.6, however when we go to a bore bigger than 99mm, we have to use a custom head gasket and upgraded rods should be used (although some people opt against it). To maximize the increased displacement at the 101mm bore, one can also opt to have port work done and upgrade to an IPD plenum and GT3 throttle body, to help optimize the top end. However, most choose to leave everything stock and increase the displacement, which will limit the top end, but will still give increased low end torque. ECU tuning also isn't required, but once again, there is power left off the table that a custom tune can find. These are just some of the examples of why you can see a large price difference between a stock-ish rebuild and a full performance build, but of the same displacement. If the car is going to be tracked, other upgrades to the cooling system including extra cooling for the gearbox become a consideration, but this is the case with any race car, stock engine or not. It all boils down to budget.

At the end of the day, consider the entire engine project before you judge costs. This isn't easy for most, as they have no idea what goes into a full build. They may think they do, because they have "researched" it, but at the end of the day that "research" doesn't go beyond Google, and Google is pretty stupid.

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Very cool Gmund! BEACH!

Beach=Good!

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Yes...YES it does!!

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Headed home today... This sitting around, being lazy crap is ending!