Is it possible to stroke a 3.4L motor to 3.6L ?

I was looking at the specs today of the 3.4 vs. 3.6L motors and I noted the following: 3.4L - 96mm bore x 78mm stroke 3.6L - 96mm bore x 82.8mm stroke Thus the 3.6L simly has a 4.8mm longer stroke Could you simple take out the 3.4 crankshaft and insert a 3.6 crankshaft instead and get a 3.6L motor? I know our heads are 3.8 S heads. The 3.4L motor has 11.1 compression The 3.6L motor has 11.3 compression Is the .2 compression difference simply that the 3.6L has less space at the top of the block when the piston is at the top? or is it that the 3.6 piston drops down 4.8mm further into the block but comes back up to the same point at the top of the travel thus compressing more volume? Anyone know?

BTW the 3.8 takes the 3.6 stroke but bores out the block to 99mm instead of 96mm so I don't think you could as easily convert to a 3.8 because you'd need new pistons, etc. and you can't just bore out a Porsche block because you'd eat through the nikasil coating on the cylinder walls.

Ken - The Cayman has different pistons than the 997 to provide proper compression with the short stroke crankshaft. Basically, the 3.4 CS engine is a base 997 block with a short-stroke boxster crankshaft to drop the displacement from 3.6 to 3.4. I think your basic idea should work, but you'd need to swap the pistons as well as the crank. I tried to get some discussion going on this topic last fall, but it didn't get very far. See http://www.planet-9.com/cayman-modifications/16155-engine-displacement-increase.html#post192375 and nearby posts in that thread. Note that CS heads are from the base 997, not the 997S as you suggest (see http://www.planet-9.com/cayman-modifications/16155-engine-displacement-increase.html#post192412 ). I gave up on the topic when it became clear that the expected power gain from the 0.2 liter displcement gain (worth about 20 HP) would not be sufficient to justify the cost of the mod. There are cheaper ways to obtain 20 HP (Softronics, Capristo, etc.).

What I should have said was that the Cayman has the Vario-Ram Plus from the 997 S, in other words the Cayman has the 997 heads (because bore diameter is the same) fitted with the 997S cams and Vario-Ram plus gear. Sorry for the confusion. I'll check and see if the pistons are different.

Even if you did this, I am not sure whats engine management you would use, it wouldn't run on the software you have on the stock ECU ?

I doubt much of anything is different, at best maybe the fuel injector delivery rate is raised a little or something, you'd have to ask Scott Slauson if he has specs on it.

How did you think of that! Now that would be the ultimate mod if its that simple. All OEM parts, no bolt-on stuff and no imaginary HP gains. Very interesting.

zal - Don't underestimate the difficulty of this mod - you must remove your engine, completely tear it down, and then rebuild it with a new crankshaft and pistons. Hopefully the rods are the same. These parts will NOT be cheap! And it will require many thousands of dollars worth of labor. I would guess a total cost of 5,000 to 10,000 USD.

Yes I am thinking at least $5K in parts and $5k in labor, but if you like tearing things apart and puting them back together, then what the heck!

I dunno about Porsche engines, but I do know someone who had his opel corsa up from 1.8L to 2.0L using the same technique! ________________________ "Sir! We're surrounded!" - "Excellent! We can shoot in any direction!" A good car will get you from point A to point B. A great car... will just get you into trouble!

Ahhh yes....."if" you are already torn down, they why not consider it? Speaking of which....what is the status of your ride Ken?

Compare the part numbers for the block, the pistons, and the rods. Let us know what you find out. If indeed it is just the pistons and crankshaft that need to be changed, then it would be a piece of cake. Turning my Jeep 4.0 into a 4.6 was a bit more complicated, but the results were worth it, particularly since the engine needed a rebuild anyway.

OK, I looked up the crankshaft, rods, and pistons on PET. They all have different part numbers between the base 997 and the CS. The total cost of a new crankshaft, a set of rods, and 6 pistons works out to $6451 (from Tischer's online parts site). If you get 20 HP (0.2 liters at 100 HP/L) from the mod, then the cost will be $322/HP, not including miscellaneous seals, bearings, etc., or labor. With labor it'll probably be about $500/HP. This will be a pretty expensive mod. Even Capristo costs less!

I believe Wendland, a tuner in Germany, strokes out the 987 motors. Check them out for info, but you may have to spruce up your German. I'll have Ina take a look for you later.

If you are replacing the crank, rods and pistons you could go for a more agressive setup. Push up the compression, shave weight off the crank and knife edge it. Replace the rods with stronger and lighter racing rods. Another option would be to go in another direction and drop the compression, doing the better rods and crank. Then go turbo and run some aggressive boost. Any way you can take the 3.4L in a number of new directions. -Trent

I think you are underestimating the other things that would be affected in the software, not just fuel injection rates and timing - there are a number of sensors monitoring your engine at any time and you can only push them so far within tolerances before check engine lights come on. Anyway, it would be a custom program which would also add hundreds if not thousands to your price. Parts $6500 Software $1500 ? Labor $1000 + I think the best bang for the buck if you are that serious is to find a local shop to build you a 1-off turbo or supercharger setup. I think cloning the Ruf/VF style supercharger designs that have been seen on the Cayman would not be impossible for a lot of shops I know about even in my small town - and I bet they would charge under $10k

Actually the blocks are the same, rods are the same, heads are the same. Crank is different Piston heads are different I'm not sure if you could "get by" with the Cayman 3.4 piston heads or not. Injectors are the same, ECU management is the same.

?? PET says 997 rods are 996 103 985 02 987 rods are 996 103 975 02 Is there a note somewhere that says these part numbers are equivalent? Am I reading the manuals wrong?? I can't imagine you could use the Cayman pistons on the longer stroke crankshaft. The compresssion ratio would be much too high, since the pistons would be pushed further up the cylinders by the longer stroke crankshaft. You might even have contact with the valves.

I was told that while the part numbers are slight different for the 997/987 rods that in fact they are the same part, just has 2 different part numbers depending upon application. I think the difference in the piston heads is where the wrist pin mounts so as to give you the proper travel and proper compression. I see Porsche wants $500 PER PISTON head. Ouch!

Tischler's online parts site has them for $410 ( http://www.trademotion.com/partlocator/index.cfm?action=searchCatalogOEM&siteid=214675 ).

For a set of 6 I might consider it, but EACH come on, they aren't made of gold you know... I can get an aftermarket set for $700 for an entire set and those are hi performance forged pistons with teflon coating.

Well, then, this is starting to be a bit more affordable. If the rods are reusable, and a set of pistons can be acquired for $700, maybe a crankshaft can be acquired from a blown motor at a reasonable price. Tischler has the new one at $2919.

Would the added increase in HP/performance warrant the expense and labor involved?

I have no idea what I'm talking about, but I note that Sharky has increased his GTR RS from 3.6 to 3.8 by putting in thinner liners (and I guess logically, he'd have to put in bigger pistons). I wonder if the same thing could be done here.

The Cayman and the GT3 have completely different blocks. That being said, the Cayman block has pressed-in iron liners, and it MIGHT be possible to press them out and install the liners from the 997S engine (3.8 L). If someone were to try this, they would certainly be boldly going where no man has gone before...

Also take a look at Autofarm (UK): AUTOFARM | Engine capacity increases for what's possible. Also see LN Engineering at "Nickies" for the Porsche 986/996 for liners and pistons. You could likely take yours to 4.0L as long as you're replacing the crank.

I'm pretty sure Lokasil is just a coating on a cast iron cylinder insert.

I think the cast iron inserts refer to these, the places where the crank and bearings go:

Ken, you must be right. I did some research and found that Lokasil is a coating on the aluminum block. So I guess there aren't any inserts at all.

So are you saying we could bore out our 3.4L blocks to 3.8 without issue? Actually it would be a 3mm diameter bore increase from 96mm to 99mm, that means 1.5 mm of wall thickness would go bye bye.

Machining away some of the Lokasil seems risky. Pressing in a larger Lokasil bore seems risky. The Nickies approach seems more reasonable to me. Porsche successfully used Nikasil cylinders for over 20 years before changing to Lokasil, and LN Engineering offers a lifetime warranty. So Nikasil does have a good service history in Porsche engines. Also, with the Nickies you can get to a 102mm bore, and I don't see any other approach that gets you there. In any case, installing Nickies and a longer stroke crank does appear to be possible, and it is a lot cheaper than a 3.8 crate engine.

It is probably not accurate to describe the Lokasil process as either a "coating" or a "liner". While a coating could be thick or thin, I agree that the term doesn't describe the process very well. But neither does "liner". The article you linked to and other sources describes the Lokasil as a "treatment", which involves an insert (call it a liner if you want) is placed into the block that is dissolved into the aluminum of the block during the casting process, in order to harden the cylinder walls. The "insert", while a seperate piece before the block is cast, becomes alloyed with the aluminum of the block and disappears during the casting process. To me, a "liner" is the same thing as a sleeve. It is a seperate piece. I'm having trouble with the concept that a Lokasil insert, designed to be consumed in the casting process, could be substituted for a sleeve. But perhaps that explains why it didn't work.