996.2 Engine Rebuild ? Anyone Gone 3.6 to 3.8L with Cast Iron Sleeves?

Hi all, Looking for some real-world feedback from those who�ve rebuilt their 996.2 engine � especially if you�ve gone from 3.6L to 3.8L during the process. I�m now at the point where a rebuild is necessary due to bore scoring (cylinder 6), and since the engine�s coming apart anyway, I�m seriously considering going up to 3.8 liters. I�ve decided to go with Rheinmetall (Kolbenschmidt) cast iron sleeves , which I know are well-regarded for durability and thermal stability � and should eliminate future scoring concerns. I�m not chasing huge horsepower gains, but if there�s a chance to bump performance while increasing long-term reliability, I�d like to do it right the first time. So I�d love to hear from those who�ve done a similar build: Who did the machine work and assembly? What pistons and compression ratio did you go with for the 3.8L build? Did you retain the original crank? Did the engine need to be rebalanced? What tuning (if any) was required afterward? What kind of gains did you see � both on paper and from the driver�s seat? Any regrets or things you�d do differently? The car is a 2004 Carrera (996.2, manual, RWD) and otherwise pretty stock mechanically. I�d really appreciate any insight, advice, or lessons learned from others who�ve walked this road. Thanks in advance for the help � ESTO Erik

Most people here are going to tell you to go with the Nickies nikasil coated aluminum sleeves or the Hartech equivalent that Slakker uses in these engines. I'm sure someone will be by soon to explain the science behind the metallurgy and try to sell you an upgraded AOS, but my understanding is that an iron sleeve or a steel sleeve is going to expand and contract with heat at a different rate than the m96's aluminum block and they eventually fail again and using a nikasil plated sleeve gives you the most proven options for aftermarket pistons. I will say the shop that did my build had another 996 with its engine out when I dropped my car off and when I asked what the story was, they told me it was the car's second rebuild and that the last shop used steel sleeves. I'd also say if you ever decide to sell it, which most of us that have rebuilt our engines would never consider because you'll take a bath regardless, I'd really be more confident having it rebuilt using an LN or Hartech product. The m96/7 sandbox is small and as these cars get more popular and go up in value, having a known name on the spec sheet makes a lot of good sense to me. I see you're in Estonia, so Hartech is going to be the move for you. I went 3.4-3.8 with Nickies. Machining was done at LN in Chicago, heads were ported/polished/serviced/upgraded with race spec valve springs by Len Hoffman in Georgia, assembly was done by Automobile Associates of Canton in CT. Used the stock crank as it wasn't damaged in my failure. Went with Mahle 101mm pistons and CP Carrillo rods as my tech that assembled it had seen some of the JE options fail on-track in recent years. You can run the stock tune with 3.8 build, but it will benefit from a tune and come alive when you're ready. Mine is still running the stock tune with 12k miles on the rebuild and I'm planning on doing a Softronic one at some point next season when I upgrade the exhaust. I gained a lot of torque in a wider band and a noticeable power boost. It really took what I liked about car's character in its stock form and balanced it to be less peaky while giving it a lot more to work with. It's not going to be Turbo fast, but it's a really, really fun drive now. My car is a base .1 Carrera with a 6MT. Good luck with your build!

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Yes, guilty as charged, I just hate to see M96/7 engines fail needlessly..........Although I could probably solicit the shops that rebuild M96 engines to pay me $$$ to stop selling the UAOS...... Slakker/Brandon told me 90% of the engines he gets are from spun rod bearings which the UAOS/UIDS cures.. Op, are those Kolbenschmit Iron Sleeves Wet or Dry ??? I now Darton makes an Iron Sleeve, as does LA Sleeve and Vision uses one as well as Jarno in the Netherlands.....but haven't heard about a Kolbenschmit Iron Sleeve for M96.....

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Well, no matter who's iron engine cylinder sleeve is used, you can't escape Thermal Conductivity properties. This is something I've studied in detail way back when in school... Top engine manufactures last century went to aluminum cylinders with a hard chrome/nik-sil type platting (it all started on 2stroke dirt bikes, then went to super bikes then cars/etc.), Aluminum Thermal Conductivity was so much better than iron that heat dissipation rates of aluminum allowed a substantial bump in compression ratio without the chance of detonation. This increased fuel efficiency/hp/torque/engine heat dissipation ability, all around performance gains. Going back to iron cylinders is a step backward from a 996 sports car performance stand point. Yes iron cylinders can be done correctly and last. But you'll have to decrease C/R for durability/longevity. Thats an immediate HP loss. So you'd better bump up displacement considerably along with cooling system upgrades for similar HP as an oem engine with less displacement. My bet, a m96 3.8 iron cylinder m96 that is set up for the long run will have 5-8% HP/FE loss compared to a oem 3.6 m96,,, depending on fuel being used. Being a flat 6 compounds the problem of C/R choice with iron cylinders, as heat rises. Now not only does the head have to remove heat, but now 1/2 of the cylinder is getting a heat bath from combustion. On v8/v6/ inline 4/6/8 the heads are much more involved with heat dissipation than the cylinders, not so on a flat 6 engine. Especially an engine(m96) with a compromised lubrication/cooling system. jmho

Allcool - So you’re saying you can iron sleeve, but why would you? Great explanation. As percentage of total cost, sleeves are a small percentage and Darton iron isn’t that much cheaper than Nikasil.

You've already heard the "don't use iron sleeves!" mantra, with which I agree, but you're gonna do what you're gonna do. If you're already going through the effort and expense of changing all of the necessary parts for a displacement upgrade, why not go to 4.0? It's a proven upgrade with a lot of history. I have a 4.0 from FSI, built from a 3.6 M96 engine. Stock crankshaft is retained. Yes to getting a tune. Engine is dynamically balanced, yummm. Worth the cost IMO.

I did 3.6 to 3.8L, and 3.8 to 4.0L, both times with LNE. No regrets.

3.6 to 3.8 with wet steel sleeves. No issues and power was gained from the displacement, despite using steel. I've put over 20K miles since rebuild. Only issue is some oil weeping from somewhere, but that's not a sleeve issue. Who did the machine work and assembly? Bodymotion in NJ What pistons and compression ratio did you go with for the 3.8L build? Mahle pistons, no idea CR - he also used customs rings and coatings on pistons Did you retain the original crank? Yes Did the engine need to be rebalanced? No idea - but the builder did balanced pistons and rods (not sure if that's a full rebalance) What tuning (if any) was required afterward? None What kind of gains did you see — both on paper and from the driver’s seat? Wasn't dynoed, but from the seat the gains are noticeable, especially in the upper RPMs to redline. Any regrets or things you’d do differently? I regret using a builder more than an hour away.

I'm in the UK and I use Westwood ductile iron wet liners in a 3.9 / 100mm application with off-the-shelf Mahle Motorsport 4032 pistons. My engine has schrick cams, flowed heads, x51 inlet etc and standalone management. Who did the machine work and assembly? Serdi Engineering (here in the UK!) the machine work, I assembled What pistons and compression ratio did you go with for the 3.8L build? 12:1 , 100mm/3.9l Did you retain the original crank? Yes Did the engine need to be rebalanced? Not sure I'd phrase it like that - I had the rotating assembly balanced, it would have been fine without. The pistons were very good out of the box. What tuning (if any) was required afterward? Started with x51 eu2 map, larger tb gave a throttle to air mass type fault code until I changed the map, I run 997 injectors as 996s max out, I've removed post-cat o2 sensors, cat warmup, secondary air injection from the map, fuelling needed a lot of work. I got the standard ecu running pretty well with 997 tvub, VE model, accel enrich and lord knows how many maps, but it runs better now that I have a standalone ecu running fuel. What kind of gains did you see — both on paper and from the driver’s seat? When first built I had it run up locally to validate a few things and saw 370bhp / >300ft/lbs with quite low trans losses (I'm rwd), it's had a bit of work since then so would expect a bit more. What I like about it is it's strong from 3k rpm all the way to 7,5k rpm Any regrets or things you’d do differently? 997 heads and 997 x51 inlet probably. But if I had a chance again I'd probably have a crack at fitting a later porsche engine.