GC996

Nice Pete. Congrats on getting it done.

plpete84

Time for a 6 month update....

After fixing the minor leak post the center radiator custom install all has been well and no more leaks. Temps have been fine as well, although I have not been pushing the car to the point where I'd see it make a difference. That will come later.

Keeping with the saying, f*ck around, find out, it was time to take a quick look at my spark plugs and inspect the bores with the borescope....and boy, did I find out! The oil consumption has been steady for 3 years now and has stayed at right around 1L in 600 miles average, which Porsche says is in spec, surprisingly. Sometimes a bit more and sometimes a bit less. The car never showed any other signs of bore scoring and all preemptive steps have been done to try to mitigate it. I recall Charles from LN mention something about an old TSB where some engines had a lower tension oil control rings, which could potentially lead to some oil burning. Yet another theory I can add to the bucket. All bores seemed to look very good and the piston tops were very clean after running Redline Si1 in the tank. All looked good until I got to cylinder 6 (I think it was). Get a load of this....



After several double takes, cleaning off the lens on the scope and some WTFs it looks like we have a problem, Huston. I'm unable to point to a particular event or time that would lead me to think something like that might have occurred. The engine has been running perfectly fine with no noise or anything that would indicate that a loose object was in the cylinder bore. I'm sure I would hear something. I took a few photos and reached out to both of my mechanics and few other folks much smarter than me that have seen things over their time working on P cars. Looking at the photo, you see the bottom part of the piston, clearly with a small chunk missing and indentations that seem to be somewhat similar in shape. Whatever was in there was now gone too. Any visible damage was also limited to what you see in the photo. The rest of the piston looked normal. Some of the guesses I received were: one of the prongs of the spark plug broke off - nope because the spark plug was completely intact; Something was ingested through the intake - perhaps but the intake has not been apart since I did the UAOS install and I don't remember seeing this during my previous bore inspection; Broken valve - maybe but the engine would definitely loose some power and compression, which has not been the case; Valve seat separated and fell in - that's the most probable guess although I have never heard of anything like that before; broken piston ring - maybe but not sure how the ring would brake, come loose out of the groove in the piston and work its way upwards through the tiny clearance. Sometimes ignorance is bliss and had I not performed my typical inspection I would have had no clue this occurred and just gone about my business with the car. It's a little ironic that in the world where the IMS, bore scoring, intermix or AOS can take my engine out this is what I got served up with ¯\_(ツ)_/¯

So what's next? I've been driving the car, albeit not as hard but it still gets driven. About 3 weeks ago or so I pulled the plugs again and things looked pretty similar, just with more carbon build up on the top of the piston. The car has been running the same as it always has. Evaluating my options I could either: 1) leave things as they are and use the car normally and preform regular maintenance as I have. I would stay off the track though. 2) New short block from Porsche and get that swapped out and 3) Full rebuild. Because the delta in terms of cost between the last 2 options is actually not that great when all said and done, I decided to go with a full rebuild. This is not a car I intend to track a lot but I would like to do 2-3 HPDE days a year for fun and knowing that the engine could go boom and have the costs get significantly higher didn't sit well with me. As they say, it always runs best right before it blows up.

After carefully considering my options and what the costs will be I elected to work with Brandon at Slakker Racing Development and a deposit was put down this week to get my spot in line. We will be utilizing the Hartech 4.1L cylinders with nikasil plating as well as matching pistons. Hartech actually has Capricorn as their manufacturer for the pistons and cylinders and is said to be equivalent to a Mahle Motorsport or better. The piston is a Hartech design that is suitable for street and endurance racing applications. Besides the displacement upgrade, this will be a somewhat of a mild build. Speaking with Brandon, I expressed that my primary objective is reliability and not horsepower. I'm sure I'll be seeing a decent bump in power but for my use case, eeking out every possible HP is not important here. Crazy, I know, but with these cars, and how I plan to use mine, getting into the neighborhood 370ish will provide me with all the kicks I need. If it's more, awesome, but I don't want to throw more money at it to get an extra 20hp. We will also be using the X51 intake manifold that should help here for sure. The way I have been thinking of the car is "what if a GT3 Touring version of a 996 existed". As I have more information and photos I'll be posting some more updates. When this is all said and done, I plan to fly out to Oklahoma, check out the whole operation and drive back to DC. Should be a great road trip and a great way to get some break-in miles in!

More to come....

2mAn

Man, one of my biggest fears, but I think that was a PO nightmare as thats why mine is currently a 3.8. He did the overbore during the rebuild process. Do you get to 4.1 from just a bigger bore? Still weird how that may have happened.

Bummed, but you seem to have a good attitude about it.

plpete84

Yeah it's a bit of a bummer but I like the car enough to keep it going. Actually, I've been driving the **** out of the car for the last 3 years racking up about 30k miles so at least I'm not in a situation where it's been sitting and now I need to drop more money into it. Basically, getting good value out of the investment so far. And yes, it is my understanding that the increase in displacement will come from the new larger sleeves that will be installed once the block is bored out. They will come with matching pistons and rings so everything plays nice together. I'm actually quite curious to see what Brandon finds once he rips into the block.

KJinDC

What a great thread, barring of course your last update. The journey you and your car have been on is impressive. While knowing relatively little about them, I have always liked the 40th Jar cars and like you felt they were the precursor to the later generation GTS cars. I have the mechanical aptitude of a drunk butterfly so, as a checkbook mechanic, I marvel at what you and others have accomplished. Perhaps I missed it, but how long do you expect your car to be out of commission while the motor is rebuilt?
I've been getting re-invested in the 996 forum of late and have read quite a few of the massive threads surrounding owners, their cars, and their builds. In years past there seemed to be more focus on what color tire valve stem caps than anything of substantive value. It's nice to see the shift in the focus of the forum.
BTW, we are actually somewhat neighbors. I'm in the Shepard Park area of DC. I've got 99 996 as a track car and have been active in the local PCA Potomac chapter for quite some time. Hopefully we can catch up (especially at the track) at some point. I'd love to get a ride in your car once it is broken in. I've never been in any of the 3.8+ 996s.

TheChunkNorris

Damn Pete that piston looks bad. After the build, your car will be one of the most sorted out of all the 40th anniversary models.

zbomb

Man, that picture made a pit in my stomach for you. Does seem likely to have been a PO mistake as I'm thinking that damage would have created a noticeable racket until whatever was in there was ejected.

Good luck my guy !

tommelton

If the damage is from PO time and you have amassed 30K+ miles on it in 3 years, that damage to the top of the piston is not likely to cause issues. Yes, it will be a hot spot on the crown, and there is surely some mirror image damage on the top of the head - but again - after 3 years and 30K miles (if existed pre-purchase) - but I think you said you did previous bore inspection and did not have the damage? If so - how long ago was that inspection?

-Tom

plpete84

Thanks! And I feel like I might have seen your car around town...happy to connect any time so shoot me a PM. Also, love the drunk butterfly analogy I genuinely enjoy wrenching on cars and detailing. It's a pretty satisfying process...until something brakes or the blow torch and a hammer needs to come out Since I just made the deposit, that should have gotten me into the queue with Brandon. I'll continue to drive the car until it's my turn. No promises around timeline have been made yet but if I'm back on the road sometime in spring or early summer I'll be happy as a clam.

Yeah...I actually might ask Brandon if I can keep it as a paper weight hah. The car number is 1111 so I have no choice but to make it great

Thanks man! One of those things that you can't really unsee. Could have been the PO but I doubt it. That said, this engine has always been a bit of a russian roulette in terms of its past so whatever was done to it previously decided to stick its ugly head out now. But hey, I'm still enjoying those Ohlins!

Tom - all good points. Last time I pulled the plugs was on Aug 6th, 2022. I discovered the piston damage on Sept 18th, 2023, so whatever happened, happened during that time period. There was one track day, a HPDC in early March of 2023 but the car ran fine during with zero issues. Being the intro to track driving there was only about 3 or so 20 minute hot lap sessions. Rest was skills practice. So yeah, I could probably keep driving and maybe be fine but I'd need to dial things back and hope I don't get to see the internal through a nice window on the side of the block that happened to appear. If that happened, it would take this experience from a bit of a sucker punch in the stomach to a sucker punch quickly followed by a swift kick in the nuts. Did not want to do there!

wdb

That's quite a picture! I've heard that carbon chunks can be pretty dense, I wonder if a chunk broke loose from a valve face or stem...? The only other real source would be something in the intake, which would have been post air cleaner, and most likely a piece of something already in there -- and I'm having a hard time coming up with something like that. A setscrew from the throttle body?

theprf

I have seen similar things happen on boosted cars when the mixture gets so rich that gases under the 1st compression ring explode, which chunks the piston like that. The dents are probably from the missing chunk before it exited through the exhaust.
I have never seen pistons blown up like that on NA cars, I don't think it is possible to get the mixture rich enough at high cylinder pressures.

So I would guess it's a piece of the valve seat that has come adrift.

plpete84

I guess there is a first time for everything! Perhaps we will know more once Brandon rips into the block. I have also heard of things like that on turbocharged cars. Part of me has me thinking and wondering if it was the valve seat and if so if this happened at startup. Valve seat comes loose and falls into the combustion chamber -> few initial revolutions of the engine smash it up causing what we all saw -> and then everything exits via exhaust. My reasoning for that is that the damage is localized to the very bottom of the piston only. I imagine if something was knocking about in there for longer we would see those marks all over the top of the piston ¯\_(ツ)_/¯

Porschetech3

It's definitely not a screw/bolt, there are no thread impressions on the piston, I have seen what it looks like when a screw falls into the combustion chamber, and you can clearly see the threads..

All Holley 4 barrel carbs were bad about the center screw falling out .Back in the day of "Carbs" lol...If you had a factory dual plane intake , the screw couldn't fall into the intake, but if you had a single plane,medium rise, or high rise intake, they were open in the center and the screw would fall right into the cylinder. I have seen it many times..most people who had been around a while always left that center screw out because they were so bad about vibrating loose and falling into the engine..Those screws are pretty big to and would beat the hell out of the top of the piston..I had a friend who had built a Round Tracker to race at BIR, a 400 SB with a Victor Jr intake, had the screw fall out about 1/4 way through the season and beat up the piston pretty bad before it blew out the exhaust,, it bent the spark plug and started missing is how he found it ,but didn't pinch the top ring ,so put a new spark plug in and kept racing it all season and won the championship....





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theprf

I can't see that being a valve seat coming loose, the engine would run terrible if that were the case.

Ah yes, the classic screw falling out... this would happen on the Schrick VR6 variable geometry intakes. Schrick uses a rotating flap that is very much like the throttle plate in a Holley, screwed to a shaft. Those screws would unscrew and since they are just above the runners for #3 and #4 the screw was guaranteed to cause much carnage.
The Schrick VGI and closely related VWMS VSR are the first application of a variable intake that I know of, dating to 1992.

hardtailer

Agree with the above regarding valve seat.
You could try a bore scope with a mirror attachment to look at the head or find a shop that have an endoscope with a controllable camera to inspect the cilinder head