https://www.planet-9.com/threads/engine-failure-recap-2007-cayman-s.98040/
FINALLY! My car is back on the road and my bank account is $26K lower. Yup, your read it right, $26K. The car looks and drives great. I’m now working on breaking in the engine on break-in oil and attempting to get the full break-in done before heading off to VIR next month.
There were many problems found in the engine after teardown so it was more than just the spun #6 bearing plus I added a few mods to help lower the chances of destroying the engine again. A previous owner obviously had abused the engine. Upon engine teardown we found the crankshaft not in pristine condition so that was sent out to a shop that specializes in Porsche and race car crank refurbishiment. This was $2000 of the tab. There is also something else that no one has spoken about and is apparently a huge problem with the M97 engine and that is the valve guides are too short and wear prematurely. The valves were incredibly sloppy in the guides so they all had to be replaced. Porsche does not sell valve guides so thanks to another poster we found a shop that makes them then they have to be custom honed. Along with that I had a full head job done, valves resurfaced and seats cut which all added another $1050 to the rebuild. The crankcase looked good and was sent to LN Engineering so they could perform their magic with resleeving with 3.8L Nickies plus they throw in JE pistons and rings. We switched out the rods to Carillos, added LN IMS bearing retrofit, billet tensioner padle, oil pump drive, filter adapter, billet micron reusable filter, and their 3.8L modified head gasket. ARP head and carrier bolts. All new chains, guides, bearings, and all hardware. I put in a new clutch and unfortunately the flywheel had a deep score in it plus burn marks so it needed to be replaced, add another $1006. No way I screwed up the flywheel, I only had the car for 7 weeks/500 or so miles and I’m not one to abuse clutches so it had to have been from the previous owner. I remembered there was some minor chatter but just thought it was the clutch needing to be replaced. Other additions included the Mantis 2L deep sump, center radiator along with a grill to put in front of it for protection. Unfortuantely with the bill hitting the flight levels I had to make a decision to hold off on the Motorsports AOS. I’ll save that until my bank account gets another infusion of cash.
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M96 M97 1997-2008 Boxster Cayman 911 Connecting Rods 986 996 987 997
So what is a cracked cap connecting rod? Engine Builder Magazine has a great article about this technology, but long story short the stock connecting rods are not truly a forged connecting rod. They are a powdered metal rod. Besides not being rebuildable, they also have about one third the life of a forged connecting rod. Add more power and raise the RPMs (track use) and the weaknesses of the factory rod start to shine through. Add to that the fact that the stock rod bolts can stretch, it’s highly recommended that you do not raise the rev limiter (most aftermarket ECU tunes will raise the rev limiter) on a stock engine. Many have even taken it upon themselves to short shift their engines when tracking the car, to prevent a rod bolt failure, and this has proven to prevent these rod bolt issues. If you have a rod bolt stretch, in most cases, you’ll have a rod bearing spin and end up with rod knock, if the engine is stopped before it grenades. If the bolt breaks, bearing comes apart completely, or rod breaks, it’s all over – you’ll likely need a different core engine from which to build an engine. It’s the 3.4 Cayman and 3.8 997 engines when tracked that seem to be most prone to catastrophic failures, so understand this when choosing to track a car that has a stock engine (be sure to address oil starvation with the required oil system modifications and use of the right motor oil for track use). This can easily be corrected when the engine is rebuilt – street cars should be fitted with ARP rod bolts (torqued to ARP’s specification, not the factory torque) bare minimum and if you think you might autocross or track the car, replace the connecting rods with forged rods. There are several brands of connecting rods available – Carrillo, K1, and Pauter, all of which are far superior to the original cracked connecting rod.