My theory on 355 exhaust manifold cracks, your comments please...

I think that yoy have a reasonable point here. My thought on the subject is that if you heat metal and cool metal doesn't it gain in strength not weaken. When making a knife or sword stronger it is heated then cooled and this helps strengthen the metal. Perhaps it makes it more brittle and subject to fractures.

 

The air pump only runs for the first min. or so, which is long before critical temp in the exhaust is achived.
I have replaced headers on at least a dozen cars now, and I have checked the check valves on all of them, having yet to find a bad one that did not hold vacuum.
The failures on the 4 headers that I bothered to cut apart have all been where 2 tubes cross paths close to one another in a tight bend. I believe it is a matter of the metal at this point being barely able to handle the heat of the exh. gases from 1 cylinder now having the heat from another pipe close by adding to the heat in the first pipe. Take that and the try to turn the gases in a very tight radius turn and eventually the cherry red hot metal fatigues and gives way.
Dave

 

My guess is that if you try and 2nd guess that particular weakness of the car, something else will get you

I'm currently sat in Starbucks in Madrid having driven my 355 3500 miles around Europe in the last 2 months, including Modena/Maranello.

So far, my alternator failed on the M20 and the gearbox speed sensor packed in just outside Maranello. I suspect I might have a blowing exhaust header now too, but this could just be a severe bout of paranoia!

I guess what I'm saying is that I'd leave the car as it was designed to work, weaknesses and all, and enjoy the trip with it. Make sure you have Euro breakdown cover, a mobile phone that works and some Euros in cash on you and you should be fine.

FWIW there's a very good Ferrari specialist just down the road from the factory in Maranello (about 30mins or so from Modena). They're cheap and very friendly and helpful.

Furthermore, in the event of problems find yourself an internet cafe and get onto the Europe forum of FerrariChat for the country you're in. The guys on there are *extremely* quick at pointing you to the nearest place that might be able to help.

While you're in Modena, make VERY sure you visit Pagani. That outfit is amazing and even if you're not keen on the look of their cars (I wasn't) you will probably be converted by a visit there. Search for Modena Design in the internet for contact details, or drop me a pm.

The Lambo museum is worth the slight detour too. I suspect you won't get into the Ferrari factory now, but the Galleria is OK and you should look at spending a night in the Ferrari Hotel (Planet Hotel) just opposite the factory if you can. We got a top floor room that overlooked the test track for 82 Euros a night (B&B for a double room). DeTomaso aren't far away either and have a very small museum you can look at. Ducati and Maserati are nearby too, but we skipped those.

Enjoy the trip and bring plenty of sun cream as southern Europe is hot at the minute.

Andy
PS Watch your speed on the French and Italian motorways.

I managed to bag a fine on the Italian motorways for a slight velocity indiscretion that apparently did not amuse one of the jodhpur wearing traffic fellows that talked to me.

Add to that the roads, which are shocking in quality at times with massive potholes appearing out of nowhere, and setting the suspension to comfort and keeping an eye on the speedo is a good idea.

 

I think Dave is right on target. I have my last failed manifold and it is just as he predicts.

 

"peak exhaust gas temperatures rarely exceed 1300 DEG C and Stainless steel melts at 1450 DEG C." Is that for pure stainless? The folks at QuickSilver tell me that "The original 355 manifolds are made of 409
(about half stainless steel) and they are only 1.2 mm thick.
The qs manifolds are made of pure 304 stainless steel and they are 1.5 mm
thick"

-Michael

 

Of course I haven't seen any of these failed manifolds, but I'm certain that the exhaust temps never reach 1300C! That's over 2300F! The hottest part of the exhaust system will be in the catalysts and even the best washcoats can't handle temps above 1700-1800F. You can use that as the upper bound on temps anywhere in the exhaust system.

 

If the tube that is used to manufacture the header is only 1.2mm nominal wall, under the bending of the tube (during manufacturing) the material is stretched out on the outside of any bends. The tighter the bend radius the greater the stretch and the thinner the material will become on the outside of the bend. It would not surprise me if the nominal thickness on the failure point were as low as something like 0.8mm. It's not surprising that the manifold suffers the way it does.
Has any one seen inside a 360 manifold? Would be interesting to compare the difference.

Paul

 

As we know the passenger side fails first, we have different situations.
Right side is a hotter place because the engine compartment is filled with
the drysump reservoir over this manifold. It causes heat jam.
Left manifold enjoys a better air circulation and therefore a longer life.
Challenge grill wouldn't help enough for this hot corner.
Hot exhaust should get quicker into the muffler where the surface is huge.
Ceramic cats avoid this.

My cool-down-config would be:
- Hyper-Flow Cats
- little Fuchs muffler for better flow and better air circulation in the engine housing
- Challenge grill
- Open throttle

Ferrari should do something for us: 22.000 new manifolds. Better ones and 4 free

forza

cinquevalvole

 

Interesting to see that fact that nobody expects Ferrari to fix the problem themselves.
If every owner encountering the problem (and there are many http://ferrarichat.com/forum/showthread.php?t=17439) wrote a letter to their national importer complaining about this unacceptable design shortcoming and claimed warranty coverage, maybe Ferrari would've addressed the issue a long time ago, changed the design or dumped Ansa as a supplier altogether.
I relentlessly rant about this, we accept way too much nonsense.

My car is having both headers replaced under warranty again, without a hint of a credible explanation about the reason while spanking new 2003 vintage headers failed like the previous ones. No lot tracking, no date codes, no PN traceability of F/F/F change. A case study for poor quality mgt.

I admire the faith of fellow f-chatters in fixing the problem, this kind of issues makes me want to dump the car.

 

Thermal shock is something that does not happen when a relatively thin piece of tubing is heated by relatively low pressure hot gases. What is meant by thermal shock is that one part of the tube wall thickness is hot while the other is still cool. The hot metal wants to expand but the cool metal does not want to do anything because its temperature is still low. This sets up thermal stress with the hotter material being in compression and the cooler material in tension. But for this to happen you need a big thermal driver or a thicker piece of metal or a piece of material with a poor thermal conductivity. None of this is present with the header. The big driver would be a high film coefficient that can supply heat to the tube wall faster than it can conduct through the wall. But since the header is so thin and is metallic (good conductor), a gas cannot supply the heat at a high enough rate. In general, you do not have thermal shock with gases.

An example of thermal shock would be putting hot water in a glass. Film coefficients for liquids are high and can supply ample heat at a high rate. Glass is a relalively poor conductor and is thick compared to a header with no ductility. That is why a glass tends to crack. When you pour the hot liquid into the glass, the inner radius portion of the glass expands because it gets hot. But since glass is a relatively poor conductor, the exterior is still cool. So the inner streaches the outer in the circumferential direction. Bingo, the glass cracks.

A back of the envelope check for thermal gradients is the Biot number. It is calculated as Bi = h * d / k, where h is the film coefficient. d is the wall thickness and k is the thermal conductivity. If that number is less than unity, you don't have gradients. So for a gas, h could be 10 at most. d is less than 1/16 inch and h is about 10 for stainless steels. Do the numbers. Don't forget thickness must be in feet. The Biot number is much less than unity.

Cracking of the headers is not thermal shock. It does not happen with gas heating.

 

All way to technical for me! I just accept that it will happen to me sooner rather than later, and when it does, will replace them with manifolds made by Quicksilver, QV or Tubi.

Not only are they cheaper than OEM, but better quality. So easy decision.

In fact, I suggest a boycott of Ferrari OEM manifolds.

It would appear from other threads that some 355s have had multiple manifold failures, where others have had none. Therefore, maybe individual cars have a characteristic that leads to manifold failure, or maybe its down to individual driver style, usage and climatic conditions.

The sad fact is, if you want decent reliability and build quality you buy another sportscar.

Robert.

 

Here are some pictures from my 355 manifolds,as we know there 2 problems the first is smog tube cracking and the first picture shows a good smog tube the 2nd one you can see the crack on the weld.the outher 2 are of one of the stock pipes that burned through,GREAT PART ,FERRARI IT CAN BREAK 2 WAYS NOT JUST ONE WAY
DAVID

 

That hole looks like extreme temperature to me. It looks like it melted.

Does the spark plug from that cylinder look like the others?

 

PLUGS ARE ALL OK ,CATS ARE CLEAR AND OK ,,JUST SH..T METAL USED IN MANIFOLD PIPES!!!!!!!!!!!1

 

Ah!

now we are getting warmer!!

Where the pipes are bent the material is wafer thin and the production is not precise enough to determine the min density for proper operation.

I think with people who use their cars they ALL seem to fail in time, either very quickly (4/5k) or at 18K.

 

there was another thread where someone called QV London, and they confirmed that they use 1.5mm versus 1.2mm and stainless tubing of a higher grade when rebuilding customer's oem headers.

 

I think it may have a Ferrari Part number howevr ANSA Products is the manufacturer of those POS headers, correct?

 

Ansa is the OEM, indeed.
My point is that, if indeed there was a change in design to address the problem, I could not obtain from Ferrari any indication on how to distinguish before from after parts, no date code, no lot number, no part number change, nothing.
The PN itself is stamped on the top of the headers, 129L01, 129R01.

I would not pay a cent anymore for that crap, but the only thing I'll get under warranty is another set of OEM parts, with the candid hope that this one will hold (apparently 2/3rds do).

 

Have followed this post, and opinions, with interest. The smog tube failure appears to be simple mechanical stress. The failure does not appear to be heat induced. Poor design.
The header tube failure is not thermal shock, as pointed out in the excellent post by Lawrence. My background is in high temperature applications using graphite and ceramics. A thermal shock failure in graphite will fissure. I assume a thermal shock failure in metal would appear similar.
My opinion, worth precisely what you paid for it, is the tube failed due to poor material selection. The tube material appears to be a low grade steel or a very low grade stainless. The failure looks like it was the result of corrosion, not excess temperature. As pointed out, the outside radius of a bent tube will generally result in a thinner wall. To be simplistic, the failure looks like the old mufflers in my beater cars when I was in school.
Ferrari used cheap material and poor design. Why upgrade an older model and fix the part correctly? Cheaper to replace with existing stock. Since, as was pointed out in another great post, the problem does not diminish sales. We continue to purchase the cars, smile and say “that’s Ferrari”. If there are no consequences, where’s the incentive to improve?
David. Heading to the Cape this weekend to work on the cottage. Will take the Ferrari if I can figure out how to fit the 3 Anderson window sash’s in the passenger side with the top down. Hope your 355 is up and running soon.

 

I will volunteer to be the registrar of complaints about 355 exhaust manifolds with the goal of getting relief from this ridiculous situation.

 

I will gladly sign my name to any complaint on 355 exhausts submitted to Ferrari. I don't expect them to do anything, but nothing ventured, nothing gained.

-Michael

 

SEND ME THE PAPER TO SIGN
DAVID
i will be around this weekend and the 355 is up and running ,email me and we will trade nos.