Guys, Thank you for your input. I am interested in hearing some engine solution options. It could be helpful to understand the source of the problem, because that would lead to understanding a potential ownership, which would obviously be helpful with financing the repair.
I wont know any answers to that, until we dismantle the engine. I plan to get it to a reputable engine builder to do that by the end of the month, but it could be December before I know what we find.
In the mean time, here is a picture of the bits that fell out of the oil drain when we drained the oil.

http://forums.pelicanparts.com/uploa...1536335052.jpg

Hi Allan..can you take a close up picture of the brake in the material and bottom of the brake on the longest piece..?Do you see discoloration?
Ivan

http://img.pccreation.net/photos/201809071832577413.JPG

A couple of thoughts. Was the piston pin and it's retainers intact? A popped snap ring and a moved pin can cause all sorts of destruction. Also, did the shop who built the bottom end use a stretch gauge on the rod bolts? Perfectly clean parts, ARP's special lube, and tightening with a stretch gauge help to get just the right stretch on the bolts. Another thing: I'm not reading too much into the failed pressure plate other than its a strange coincidence. I've seen two different pressure plate diaphragm springs fail, and both were in grocery getters. One a Toyota and the other a Chevy. Remember, the diaphragm is bending all the time, so a metallurgical fault can easily create a crack. I cant see how high revs would create a crack in the diaphragm. A crack in the flywheel or friction area of the pressure plate is where I would expect to see damage from high revs or excess slippage.

Redcoupe,
I agree the clutch pressure plate diaphragm failure is probably unrelated to the engine detonation.
The engine builder is a small shop and dedicated to classic Porsches. Clean environments and meticulous methods are the currency of their reputation, however we will hopefully soon find the evidence we need to verify these failure causes.
I also don't believe the engine was overstressed.

The Eurospec version of this motor came with a 10.2:1 single plug design.
Porsche made & still makes engines that run at 11 or even 12 to 1 compressions.
This engine was built to accommodate a slightly higher than standard compression ratioat 11.2:1, but other than that everything else is an over the counter bolt on modification. By all accounts the engine work is a fairly mild modification and 255HP is not such a volatile stress that the motor should detonate after 11 000miles of sensible/informed use.
Investigation is definitely needed to get closer to cause, which will also ultimately help clarify any potential cost sharing.

http://forums.pelicanparts.com/uploa...1536427431.jpg

My opportunity is to decide if I go back to a standard configuration, or if I use the unfortunate circumstance to build a different bottom end, since the top of the motor is ready for a high flow, twin plug configuration.

• Standard 3.2
• Higher compression 3.2
• Standard compression & increased displacement (3.4 or 3.5)
• Higher compression & increased displacement

3.6. It will be more powerful, more reliable, and probably less expensive.

Steve

I had a 3.6 motor with ARP bolts let go while racing shifting from 4th to 5th motor was new with Wossner 11.5 pistons everything done. So after talking to some engine builders that first thought was piston failure Alan at Asse motors told me about Glyco rod bearings DON"T USE THEM!!! spend the money for clevitte! Glyco is OK for others but not for Rods I also had a clearance grind put on the crank this allow's for more oil film on the rod bearing seems with high compression the oil film is pushed out causing seizure of the rod . Were you using Race fuel if not that's to much compression for single plug you should not have drove it. The stress you put on it probably helped cause this.

Oh and after buying Glyco bearings for the rebuild I saw where they are made everywhere some in Europe some in South America the rods MEXICO!!!! really? no wonder they are junk

Hi to Laguna..i have experienced the same problem with Glyco bought in Germany from Porsche dealer.They were made in Romania...from that point here you have to ask Porsche if the bearings are meda in Germany or not....the only little problem was the engine had to be taken a part to replace the main bearings again..no big deal since here was no damage done just extra time spent.

Ivan

I'm trying to figure out what the smaller bits are. From the pictures they don't appear to have the same finish as the rod bolts. Do they have what appears to be a ground finish to them?

Can you post pictures of the smaller bits from different angles. They appear to be cylindrical pieces. The three pieces look broken on one side and flat on the other.
I'd like to the the "tops and Bottoms" of the cylinders. if possible.

That's some real odd breakage.

The angled breaks are characteristic of brittle materials twisted off, that is exactly what a piece of chalk will look like if you twist the ends until it breaks in the middle. However, rod bolts aren't near that brittle, note the larger piece that is bent but not fractured. And the other end that is squared off is also puzzling, why would single bolts break in two places?

Are you sure those are ARP? There have been fake arp bolts found in the marketplace made of substandard material. It is hard to tell from the picture, but when I have used arp, they are almost jewel like in finish, not rough at all.

Will be very interesting when you open it up.

Sorry to hear of this, we saw the exact same thing happen on a 3.2 freshly rebuilt from a very reputable rebuilder here. After disassembly he concluded that a moment of distraction made him forget to use Lock Tight on the nut and caused the exact same breakage as yours.

FYI; He also replaced the block to honour his reputation !

To use or not use Loctite is likely to open up a giant can of forum worms!

Thank you for the great input and Im sorry about the delay in responses.
I spent the last week in wedding mode, marrying off my oldest daughter and hosting family from all over the place.
I leave for a work trip for a week and when I return will work on getting the car to a reliable place to break the engine down to see that happened.

When more details appear, I will be back to keep you all updated!

http://forums.pelicanparts.com/uploa...1536961073.jpg

Congrats on your daughter's wedding! Events like that kinda put everything in perspective! (As well as drain your bank account of funds available to fix your Porsche!)

Finally got into the motor
 

After the busyness of the year end, we were finally able to get into the motor. Through careful disassembly, we were looking for any signs that might give indication or cause for the detonation. In the end there was nothing that was obvious to see, that could have obviously provoked the #6 rod to come through the case.

If there was an over-revved cause, I suspected we might see some impact marks from the valves on the crowns of the pistons - but there were no marks, the valves and the springs are still good. The bearings were all still good, as is to be expected from a motor with 11 500 miles on it.

What is noteworthy is that both ARP conrod bolts broke, and both still have the nuts attached to the bolt ends. One fell out the bottom of the case through the oil drain plug and the other conrod bolt end (with the nut still attached) got impaled into the inside of the case, and produdes a little through the outside.
The other item to note is that; at installation the ARP - 2000 conrod bolts were all a polished silver in color with black ARP nuts. When we disassembled the motor, 8 of the bolts were still silver, but 4 were now black. Not an oil tarnish that could wipe off. You can see the color changes in the photo's below.

All the ARP conrod bolts have been shipped to ARP for analysis. Im hoping to get conclusive remarks from ARP that can lead to a better understanding of the cause for bolt failure.



http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

http://forums.pelicanparts.com/uploa...1546638527.jpg

Stock bolts are black. Hmmmm.

Thanks Allan for updating this thread.

Things could get interesting from a responsibility/liability standpoint.

2 sets of 3.2 cases in classified section today.

Hello,Will be interesting to hear what the "bolt maker"says. The part that is embedded in the case looks like the nut is partly unscrewed. The broken bits look like they have been cracked for a while? (Bright/dull surfaces). Sorry to read/see such carnage.regards,Michael.

Gosh, Allen, just found this thread. My sympathies. It seems really strange to me that both rod bolts broke. That must have happened more or less simultaneously, or the car would have made a big enough racket after the first one broke that it would likely have been shut off.

I'm curious if our cast of renowned engine builders (and I mean that sincerely--some top guns here) have seen two snap more or less at once. Anyone?

What are the chances that the rod broke taking the bolts with it?

I don’t know anything and I’m just repeating something I once heard, but in going up to 3.2 design, didn’t the factory leave less meat for the rod bolts? I thought I’d heard that stock 3.2 rods are weaker than stock 3.0 and more prone to failure than earlier or later engines?

I’d be interested to hear if this is true or not?

Thank you for this helpful tip. I've been scouring the usual sources looking for usable cases!!

On the surface this may sound like a dumb question - and I don't question that genuine ARP hardware is of a very high quality, and that in building an engine for extremely hard use (such as in racing) nothing but the best should be used - but why shouldn't stock (new) Porsche rod bolts have been perfectly adequate?

Any pictures of the bottom of the rod, or that crank throw?

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Two of the break surfaces look like fatigue failure. Smooth beach then an area of rapid crack propagation. Hard to imagine the rod nuts could have backed off without the piston running into the head, especially with that high compression ratio. My vote is bad or over-tightened bolt(s) on that rod. Could have been just one, as soon as it went the other would be overstressed and fail. If so, only one bolt would show fatigue, the other should show ductile failure. If two clean breaks, then two bad or over-tightened bolts, breakage of one hastening crack propagation of the other.

Dan

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Was it possible to check the torque on the other rod bolts during disassembly?

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John is ( as usual) correct

Subscribed. Sorry for loss.

I'm sincerely sorry for that happened to you mate ,

A friend has been victim of the same break .............it's mechanic , and that happens , even it's rare.

https://i79.servimg.com/u/f79/13/86/10/18/carter10.jpg

For reference



http://forums.pelicanparts.com/porsche-911-technical-forum/64438-rod-bolt-failures-carrera-3-2s.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/240426-3-2-rod-bolt-help.html

The Carrera rod bolts have been a known weakness on the 3.2 for decades. Original bolts are always upgraded on a rebuild, even if it's a stock rebuild otherwise. ARP or Raceware are the common choices.

Is a shop in Dallas doing the tear down?

Curious about this as well, would like to hear more opinions on shops in DFW. I have heard DC Racing is good, and some others but would like to hear from some actual customers.

Thanks, that's why I asked the question............part of a learning process.

A dropped valve once ended up with a cylinder fracturing and the rod sawing a slot in the case at the spigot in an engine of mine (over rev caused valve issue). The connecting rod cap was distorted so that only the outer ends of the cap were still touching the main part of the rod. So the high strength aftermarket rod bolts were stretched. And bent. And you could see where they were narrowed where they stretched. But they didn't break.

ARP will let you know if any non-ARP bolts were involved. Though given how gently you say this engine was used, I'd have thought stock bolts would have worked, at least until you started putting the pedal to the metal.

Modern engines are able to use higher compression because of better spark plug placement, the use of knock sensors, and the ability of the ECU to change things on the fly based on what sensors are telling it.

Did the shop doing the disassembly by any chance have access to the bolt stretch figures used in assembly? If so, did they check the stretch? This could tell if other rods had overstressed bolts. But since A did the bottom end, and the shop you are using now did not, I don't suppose this was done? Though you could still test for this - measure the unbroken bolts, reinstall them and stretch to spec. Then loosen the nuts and remeasure to see if any of them were stretched beyond their elastic range. This should not happen, so if it does it suggests at least some of these bolts were bad/wrong.

Those main bearings look great. How were the rod bearings? What did the bearings which must have fallen out of the rod with the broken bolts look like? Was the broken rod discolored, as in a lubrication failure or some other issue like wrong dimensions somewhere?

Hey Allan, what did ARP conclude regarding these con rod bolts?

Not sure what you could have done during your 30 foot test drive to a stop sign. However, no telling what occurred during the repair shop's test drive.

If the shop isn't showing any signs of contrition, I would take the engine to an independent shop for a forensics inspection and written report. You could show this to your engine builder and/or an attorney.

It sounds like a rod nut wasn't tightened to spec, but that's just my guess. If detonation was the cause, there should be signs in the combustion chamber and the affected piston/cylinder (e.g. melted/deformed material).

Sorry to hear that.
Sherwood

From what I remember the factory original rod bolts were fine and long as the engine was never over revved with a money shift downshift. I used ARP bolts on my rebuild "just cause" they were not much more expensive.

Sorry for your loss. It truly sucks.

Man that really sucks..... sorry this happened. Please keep us updated on any new relevant info.

He hasnt logged in since March of 2020..