Woah, does that last one on the right look a little wonky too, or is it just being at the edge of the photo?

So you have a bent rod(s) from.... what? Certainly not the piece of missing plastic.

The stock rods are cast, not forged, correct?

Anyone else ever break open their block and see something similar?

Ed

 

Yeah, those two issues are not related.
There were a few things we actually found, so overall it's been a good idea to get in there and do all these things right.

I'm running a lot of power. This tells me it's right at the limit of internals.
I'm upgrading to Carrilo's and some other goodies to harden the engine up

 

Got it. How many horses does it take to get to the center of a tootsie pop... ooops I mean to bend rods?

And.... what else showed signs of stress from power?

Ed

 

Wow, good thing you took it apart then.

 

Oh crap, I ran a similar tune on my 68s, fingers crossed the rods are okay....

 

I never dyno'd it but conservatively I think it's around 600 to the wheels and also roughly the same in lb ft in torque.


Hey Bogg, yeah I was actually surprised too. You can't see it easily, but all of them are actually bent.
Some claim that these engines are good to 1000, but frankly I think it would be prudent to update the rods at the 600 WHP range to be safe.

Mind you, my car is driven hard. I suspect this is the result of continuous strain over long and recurring use.
Not a catastrophic failure but over a course of 50,000 km at high HP stress/strain - seems very plausible that fatigue sets in.

PS. I'm reconsidering the 3.8L build.
Just getting details finalized with the three musketeers... Sam, John, and the resident expert, James @ SCAN here in Vancouver.

 

I did dyno the 68s and they made about 575whp on a Mustang 4 wheel dyno. About the same for tq. That translates to low 600s on a dynojet. The tq peak is at a lower rpm with vtgs vs my xonas. When I had my xonas installed the leak down test was fine which I believe implies the rods are ok. I will repeat the test when i change the turbo boost lines this winter.

 

Aaah yeah you may be fine in that case.
My leakdown numbers were very high, and found leakage coming through the valves and into the crankcase apparently "of significance", so that's very likely the cause of the high oil consumption I was seeing.

 

no child left behind....
101,000 miles on the car (daily driver)....I am glad she let me down this easy.


so....to build or not to build as well.

Going to follow your journey here while I decide.

 

Block sounds? Rod slap? Or do you think it is top end and cam noise? Or..... intermediate shaft with bolts that have walked loose?

I think hearing it, it might be the third option. If it is you can intervene before the engine grenades. I would get in touch with any engine builder (I have heard EVOMS has seen a few intermediate shaft failures) and let them listen to the video.

While it would be a lot of work to get at it, catching it now will be much less expensive, though with the engine halved, you have access to everything for a build. From what I have read, the GT3 intermediate shaft is a better design with no bolts.

Ed

 

Is the intermediate shaft on the driver or passenger side? The sould seems to be loudest on the passenger side. The car idles smoothly, no smoke anywhere, and no CEL....so I dont think it has done permanent harm anywhere.


The car is officially parked. That is what I meant about letting me down easy. I was literally at a light and an suv pulled next to me and I immediately heard the noise reverberate off the side of the SUV and pulled over. Something is not right and it must be cracked open to be fixed. I am at peace with that.



My whole dilemma at this point is that I have an 11yr old car with 100k miles that could potentially swallow another $20-$30k just on the engine rebuild.

Money....which could also be part of a nice down payment on any of the following:
1. 2016 AMG GT S --> $80k
2. 2016 Mclaren 570 --> $145k
3. 2016 BMW M5 --> $45k
4. 2014 911 Turbo --> $100k


I am going to take out the oil filter and cut it open to see if there are any shavings or other foreign material in there. Fingers crossed.

 

It could be a lifter if the oil is clean.

 

Look at the picture in post 46. The large gear/shaft to the right of the crank shaft is the intermediate shaft (the one with the chains around it). However the orientation of the block is 90 degrees from the way it sits in the engine bay assembled.

So the IMS is directly below the crankshaft in the center of the block.

Yes, it will be expensive to get there, but if it is just the IMS, it is not terribly expensive (I think around $600) but the GT3 part does not have bolts, though I would imagine some serious loctite would prevent the bolts from backing out, though depending on the potential damage to the gear may indicate replacement. I think the GT part is triple the cost though.

This all assumes it is a IMS issue. Do you have a mechanics stethoscope? Also getting one of the engine building guys to listen to your video would be good.

Ed

 

I'd bet that is a lifter. It seems in rhythm and not like a bucket of bolts banging around.

 

That would be much easier to deal with. I have heard neither noises on these engines, so I am no good for diagnosis. If you have a steth and can confirm it is from the top right then it probably isn't a loose IMS.

I have been doing a bunch of reading on engine noise and have seen everything from bad mufflers, loose heat shields, normal noise, IMS and even this solution on a 996 Turbo forum:

"Bloody hell ,, two years of angst ,,, exhaust in and out,,the rattle ,,, turns out to be the part number 996 115 661 72. A thin protector plate that separates water pump hose and the fan belt going around the crank pulley. There are four screws that due to age ,, salt ,, gets eroded and comes apart. Worth checking .
My car sounds normal again apart, from Mezger symptoms."

In that same thread there was this video of a noise, but never any solution follow up:

https://youtu.be/9aLEYcY0iDo

And another one from someone who regularly creates a video to compare and see if the noise is changing (he reports not):

https://youtu.be/kUVMbr8Qhik

I found another post (again not our exact engines) but the thrust of the article was based on a TIP car and when placing the car in gear the noise would go away, indicating a harmonic balance thing going on. Here is that posts text:

"There are several noises that can be heard from these engines that sound very much the same, some of which are caused by serious engine failures while others are relatively innocent.
This makes diagnosis very difficult without comparative experience and other tests.
To explain the difficulties - typical noises that are serious are caused by the following.

(1) Crankshaft bearing failure €“ big ends or main bearings (or both) €“ usually caused by wear on the rear main bearings lowering the oil pressure just there and consequently therefore lowering it to the number 6 or 3 big-end (because the oil flow path travels to the main bearing first and from that up into the crank pin/big end area).

The noise from this sounds quite heavy and increases with revs and is present as the revs rise or fall €“ usually louder if the engine is hot.

This failure of the main bearing white metal in the shell is caused by crankshaft bending or flexing increasing the wear loads on the shell due to the large overhang at the rear of the engine to accommodate the two chains being driven there for the camshaft system. If the engine is being used for aggressive braking or is over revved - this can bend the flywheel end of the crankshaft so much the starter ring can touch the bell housing inside. The dual mass flywheel is a contributory factor as it is so heavy and relatively poorly balanced as it wears. For most racing applications in other cars with similar dual mass flywheels €“ they are removed to reduce the weight and improve balance and replaced with lighter solid flywheels.

(2) A fuel injector can also make a tapping sound that varies with throttle opening (and consequently with revs) but usually if you rev the engine and then shut the throttle €“ it would not make the sound as the revs fall because there is no fuel passing into the engine (the injector pulse is switched off).

(3) A hydraulic tappet is the usual diagnosis for a slower noise than at crankshaft speed €“ more of a ticking noise. It often goes away after the engine has warmed up (as the hydraulics pump up the tappet) but can also be caused by the top of the tappet actually wearing away (or even creating a hole through the top) in which case it is permanent. Wear in the tappet housing can also reduce the pumping efficiency of the oil transfer from the oil delivery system into the tappet.

(4) The Cayman S 3.4, 996 3.6 & 997 3.6 &3.8 engines can have damaged pistons and scored bores €“ usually after about 50 to 70K miles. The damage is like seize marks on one side of the piston (the reasons and causes of which we understand and can remedy during a rebuild) but the extra piston clearance that results allows the piston to tilt as it goes over top dead centre and the edge of the piston just touches the cylinder head making a tapping noise. This can be checked for by putting a camera (often called a bore scope or boroscope) to look inside each cylinder. The damage usually seen on bank 2 (cylinders 4, 5 & 6) on one, two or all three bores (because on this side of the engine the thrust load of the piston is on the hotter part of the bore whereas on bank 1 the thrust side is the coolest) . The damage seems to take some time to gradually get worse and initially can be present with no symptoms at all €“ gradually increasing oil consumption and slightly less sharp performance (that many owners do not notice until they receive a rebuilt engine back and remember how crisp it used to be).

(5) Valve seats. It is not unknown for a valve seat to become lose in the cylinder head and bend or break a valve €“ early signs would probably be an intermittent tapping noise.

(6) A worn IMS bearing (or a worn or damaged chain) or swarf trapped in the scavenge recirculation pumps, or damage to the chain sprockets, or wear on the chain slippers, or worn hydraulic tensioners €“ can all throw up a ****** in the engine system as it revolves which can emanate as a tick.

(7) You will probably be sceptical when I tell you that the exhaust manifold can also make a noise exactly like a metallic tick (but believe me it can and I won the bet to prove it!).

The bolts that hold the manifold to the cylinder head rust and the manifold becomes slack. The gasket is a thin metallic one with small ridges to seal against the surfaces, but it doesn €™t fit too well leaving a very thin sealing face between the exhaust port and the exhaust gas recirculation (EGR) ports. All heads have the grooves for these ports cast in and some are drilled through to inside the exhaust ports while others are not €“ and some have an EGR system on the car while others do not.

The ports connect all three cylinders on one bank together. When the slack bolts and thin contact result in a gap appearing between the exhaust port and the EGR ports, at tickover €“ the cycling of the pulses makes a very metallic sounding noise that goes away as the engine falls in revs but is there as it increases from low to medium revs (very like a tappet getting quieter as the revs and oil pressure rise €“ but tappets would still be noisy as the revs fell €“ but not the exhaust system as the throttle will be closed and the exhaust pulse of little or no intensity).

(8) SOMETHING ELSE" <-- this is where he talks about putting it in gear and lowering the noise

It seems that most of these posts/information relate to non turbo or 996 cars, and since I am sure yours just developed not much of this applies, but I found that sometimes reading everything I can jogs something that makes sense and leads to a solution. Sometimes getting there takes longer than I would like, but I try very hard to avoid the "just start replacing stuff" without a diagnostic procedure indicating the probable source of the issue.

I'll keep looking. WHile my car makes some noise, it is nowhere near some of the posts I have heard (again mainly 996 TT's) like this one:

https://youtu.be/c3Lyz8MXOKk

There just doesn't seem to be many videos with noise in the 997 TT forums. I heard one but that was WOT and sounded completely different (and nasty as well). I think the list above along with a steth along with someone who has worked on multiple 997 TT engines listening to the video will help figure out what is going on.

Ed