Sorry to see that Eric. Spooky to say the least, could be that cylinder was dropped at some point in it's life or maybe the casting had a flaw. That burn through is unusual, where you running race gas?

Castings can have flaws. They crack due to thermal cycles. Happens to all other aluminum & iron heads all the time. Even if rare in the porsche world they aren't immune so I wouldn't beat yourself up over figuring why. Replace it, check everything else out, reassemble and be on your merry way.

Cool pics though :)

Certainly could have been, but it's difficult to isolate the cracking sequence - it's obviously worst at the notch but that doesn't mean it started there. From looking at the intake stud and the threads in the chunk they are very clean and there is no indication of any crud but that is about the extent of my visual forensic capability; I'll bring the parts by some time and see if you find anything else. It also doesn't appear that the crack on the intake went all the way through (until we "helped" it) such that it could have been the source of an air leak. I have another view that shows how the crack went around the surface where the head stud nut was tightened; this also looks suspect to me.

No issues of this sort. :) As VaSteve referenced, "ironic" would be an understatement...

I experienced denotation that was bad enough that it broke rings in a cylinder back in late '04. There was no obvious cause but I had been on a trip to Canada where the highest octane fuel available was 91, and who knows if that was actually in the tank. As a result, after the total rebuild I made changes to the most likely contributing factors: replaced the chip with a "safer" one that can run on straight 93 octane, cleaned and flow-matched injectors, installed an auxiliary oil cooler, rebuilt the alternator, and started blending race gas to have more certainty of the quality and octane level. My average blend ratio is 1:1 race gas to pump premium; as low as 1:2 on really cold days, and 2:1 on really hot/humid days.

Certainly could have been a casting flaw, metal fatigue or improper torquing. However, the most common opinion is that it (1) ran lean, (2) overheated, and (3) cracked. While we might not be able to determine the initial cause, I want to do my best to figure it out so that if possible I can prevent it from happening again.

Hey Eric- what a shame. What did Steve W think? Coincidentally I was emailing him while you were on the phone with him the other night.

As per my email, I would send the 6 injectors out to have them checked. Especially if 2 other heads are showing cracks as well. I'd want to know if any of them were not flowing properly and causing a lean condition. Short of a pure mechanical failure, that would seem to be the most logical cause, though that cylinder isn't pure white like a lead condition might indicate unless oil was getting in there right before it broke.

Someone mentioned rodents nesting in these engines? I just completed the teardown of my recently acquired 3.6 last night and there was a big nest on top of #6, with all sorts of crap jammed down into all the fins of that barrel. Most certainly would have caused serious overheating problems on that cylinder if I hadn't torn it down.

So you going to have Steve W do the same valves and cams he's doing for me?

I thought you were keeping your special project a secret...:)

Steve's opinion is that while bad casting/metal fatigue/improper torquing can occur, heads most often crack because they been overheated, and they nearly always get too hot because they ran too lean (pre-ignition, detonation, crack). Possible suspects not yet ruled out include insufficient fuel caused by a bad injector or faulty management system or an air leak.

All injectors are being cleaned and flow-matched. Point of clarification - the other two heads are not cracked at all; however, when the first head cracked the fitment between the heads and cylinders was compromised only enough that you could see that small tell-tale carbon indicating some exhaust gases had leaked between them. There doesn’t appear to be any damage to those heads, but one consideration is to replace them as well.

Visible evidence of the metal surfaces shows that the other cylinders are all burning perfectly; rather than the signs you would expect to see with a lean condition cylinder #1 is actually showing the blacker after-effects of the crack. It is possible that the lean condition happened in the past and the consequence manifesting now.

Glad you found the nest in your new/old engine! It certainly happens, but wasn’t the case in my failure.

I’ve thought about valves and cams, but want to continue with it in stock form. I’m basically doing rings, valves and head studs for a fresh to end, adding some reliability bits and replacing most of the rubber in the intake system. It's plenty capable as it is and doing it right means that I'll be happy with it for a long time...me or someone else should a 997 GT3 ever make it's way into my garage!

I am. You won't tell anyone will you? :D

Heads will be on their way to Steve tomorrow. I'll split the case in a week or so and get the rod on their way shortly thereafter.

Good to hear the other heads aren't cracked. I may have read between the lines based on your email a few days ago. So just one head and a fresh top-end to be good for another 15K miles? Good to hear.

But why limit your sights to a GT3, go for a GT3RS or a Cup Car. It's only money.

Sorry to see, but maybe this is that sign your were looking for to make a change in cars? Good deals on tracked prepped GT3s out there this winter!

As much as I would love to have a 997 GT3, and I still plan to get one someday, I'm afraid this expense warrants keeping the RSA a little longer.

And for the good news: I picked the car up from ASG last week and put some break-in miles on it over the weekend. Had the oil changed this week and everything checked out, so the RSA is back in business!

Funny how not driving your car for four months makes it seem like it runs great. But it sure runs GREAT!

Now if I can just break away from work...Hello, VIR!!!

Congrats on getting it running again. Enjoy.