Pac996

Is anybody that cleans up the engines reapplying cosmolin to the engines?

Charles Navarro

As the person who took that picture, I'll add something to this discussion. Yes, the early 3.6 castings had the same amount of parent material in the liner area on both the water jacket and crankcase side as the 3.2 and 3.4. The later 3.6 blocks are shared with the 3.8, which again the only difference is the thickness of the casting parent metal. There definitely is a difference between the castings. On the later 3.6 castings, I would expect the bores to stay more round than say a 3.4 casting, as we already know that the 3.2 blocks have less issues with cylinders cracking, d-chunking, or going out of round compared to their thinner 3.4 brethren. The walls on the 3.6 are of roughly the same comparable thickness as a 3.2 on these stronger blocks, so I'd expect better life out of them for sure.

The later 3.4 blocks (like on the Caymans), do not have these improvements. We see lots of these blocks and it's interesting to see the differences and how Porsche maintains product differentiation to maintain the superiority of the 911.

The key to keeping them round is to keep them cool. We joke that the coolant temp light is the "rebuild" light.

nick49

When you guys speak of the cylinders becoming out of round, by how much? What is the greatest amount that you have seen and consider it still runable?

Also, I'm assuming the out of round is distortion rather than wear, is that correct? Are the cylinders originally finished with torque plates bolted on to simulate distortion from the crank support girdle and heads? Or are they finished in a relaxed state? Could the measured out of round be dimished or eliminated when the motor is fully assembled and at operating temperature?

Sorry for all the questions, I just find this motor rather facinating and have since I first read about it in Road and Track in about '96 or so just prior to the first production vehicles being released. The main reasons I bought a Boxster and later a Carrera. TIA

knfeparty

Engines are like bullets. They're only good for one thing, so use them for that intention!

nick49

I always thought of them as a tool

Charles Navarro

As there aren't any published specs for the lokasil bore that I am aware of, I'd say anything over .002" ovality is too much. Most of the blocks we get here for re-working have at least that much and upwards of .005-.006".

The bores are finished straight and that's how we do them. We did tests years ago and found that trying to use torque plates and simulate actual engine parameters was a crap shoot. You get the best results with a bore as round as possible within .0005".

htny

I have always been under the impression that the (M96) 3.4 and 3.6 shared the same 96mm bores, just different strokes. Is that incorrect?

Charles Navarro

Yes, the castings for the blocks are the same between the 3.2, 3.4, and 3.6. The 3.4 and 3.6 share the same bore size, just the 3.6 has a larger stroke. When they came out with the 3.8, they updated the castings to provide more substance to them for the larger bore size, which then the 3.6 block by default received those upgrades. From best I can tell, the 3.4 engines in the Boxster and Cayman did not receive those updates, retaining the design of the earlier blocks with exception of added windage notches where specified.

Wanderer

I have a 2008 Cayman S and would like to increase the displacement and making it a "bulletproof" motor, but from the sounds of it I am better off scrapping the idea completely. What are the choices here if one does not want a 911 but wants a Cayman?

Macster

You can increase the displacement with larger bores and possibly even a stroker crank.

The big bore kits use special sleeves that interlock at the top and create a nearly closed deck which helps strengthen the engine.

As for bullet proof aftermarket high performance pistons, rods, crank, and other hardware can go a long way to making the engine more robust.

Check out www.flat6innovations.com for info on big bore kits.

Uh, check that. I just visited the site and only 2.5l and 2.7l engines are supported. You can give the shop a call though and see if it has anything planned for the 987 3.4l engine.

Overseas, there is Autofarm and Hartech both located in the UK.

Another path is to remove the stock 3.4l engine and install a 3.6l or even a 3.8l engine from a 997 car, probably one from which the engine has been salvaged.

One might even buy one of these engines but I bet the cost would be prohibitive.

But as the saying goes: Speed costs money. How fast you wanna go?

Sincerely,

Macster.

Jake Raby

This is not the design that the LN/ Flat Six Innovations incorporates. We keep the deck open 100% as factory..

Charles Navarro

We actually offer our Nickies for everything from 2.5 to 3.8L M96/M97 engines and are developing kits for the 996TT/GT2/3 as well as the newer FI engines, but it won't next year before you see anything for the DFI's until it's been thoroughly tested by Flat 6 Innovations.

Wanderer

Thanks for the great info gentlemen. This gives me some things to think about. I have been tossing around going from the 08 to an 09 for DFI but if I can build a very strong motor and keep the 08 I would prefer to do this.

I like the idea of getting a 3.6 or 3.8 from a 911 donor car and building on it.

Cheers

Macster

Thanks. I've only seen pics of the AutoFarm sleeve solution and the top of the sleeves come together to form a nearly closed deck. I say "nearly" cause where the sleeves comes together they are not fused to each other.

Sincerely,

Macster.

BruceP

And so yet another generation of Porsche owners secretly anticipates the day their motors wear out so they can justify a high performance rebuild.

It seems the 996 is a 911 after all.