355/360 exhaust manifolds stats

I've had trouble posting pictures so if they don't come out send me your e-mail I'll try to get them to you.

I've spent the last two weeks researching my exhaust manifold burn through
that I experienced on a north Cascades drive. Mine is a '97 with 18k
miles on it. One of the guys in our group advised his '99 burned through at the same mileage.

What I've learned is that FNA will not stand behind this sort of failure
eventhough all the data points to a design and material error (they made the
manifold out of .12" wall thickness semi-stainless steel that gets too thin
during forming the manifold and its a poor material). The current
international wisdom I can gather from here is that all F355s will experience this problem sooner or later.

I've removed both of my manifolds and am sending them to QV in England to
have them reworked using .15" wall thickness pure 304 stainless. They have
reworked a 100 F355s so far with no complaints. Their charge for this is
L980 ($1800) for the pair. Tubi has a fine product also in pure stainless
but the cost at $5000 seemed to be ridiculous for a pair of manifolds. Tubi
does not use a rigid heat shield like the OEM or the reworked OEM from QV so
there may be a minor heat issue with the proximity to the alternator with
the Tubi installation. This is unconfirmed.

As I have later found out I may have put my exhaust valves at risk by
driving the car the 300 miles back to my home with the burn through in
the manifold. So if you get one of these failures (sounds awful) shut it
down and have it towed. Some mechanics on this Chat believe there is a
strong correlation between these burn throughs and valve failure later on.
The reason being often people continue to drive the cars without attending
to the problem immediately. I tried to baby the car on the way back so I
don't know where I stand.

I could have taken the car to Alfa of Tacoma and had the manifold replacement done at a reasonalbe price, but the car has to sit a couple of weeks while QV reworks the units and returns them. For that reason plus the minor saving, I started wrenching on it so that it could stay in my garage and I could detail the engine bay while waiting for parts. Except for having to
remove/reinstall the oil tank, the car is amazingly easy to work on. I had
the manifolds off in just a few hours - and that includes learing how to
think Italian. I'm in no rush. The key to doing this is a special 13mm
Snap-On wrench "FHOM13A" that I bought for $40 on QV's recommendation and the fine help I received from Mondial86 here on the chat. The
manifolds and the entire exhaust system bolts are almost all 13mm. Everyone
that decides to work on 355s should have one of these. I will still see if
I can hire Carlo at Alfa of Tacoma to make a "house call" to check out my valves to see if they are ok and I'll do the grunt work to put it back together if he says they are.

The other thing I am doing is getting rid of the OEM cats because many think
as the Cats deteriorate, the flow blockage increases the heat in the
manifold aggrevating the burn-through problem. I've purchased the
Hyper-flow Cats for $2290 that everybody here believes will perminently fix this the back pressure problem with the deteriorating OEM Cats:
http://www.hyper-flow.com/355.htm.

The following photos show:
1. Right Hand manifold where problem occurred.
2. Burn Though at the 2nd from the rear port (Black spot is the
burn-through)
3. Exhaust ports on the right side of the engine - There is no carbon
showing in the 2nd from the rear port.
4-7. Starting from the rear going forward. Detail look into the ports.

The fact that there is no carbon showing in 5th picture means that this 2nd
from the rear cylindar was either running very hot or the burn through
changed the aerodynamics so the soot was scrubbed away. On the left cylindar bank, the carbon patterns were very uniform port to port where these are all over the map. I believe this indicates a side to side difference in back pressure probably from the OEM Cats. It may have actually been the CAT on the RHS that started this whole chain of events. If it is this is an extremely insidious failure as you really could hear, see smell any side to side difference. I wonder if there is a stronger correlation of later valve failure to CAT failure and the manifold burn throughs are a subset of that?

If there are any experts out there, let me know what you think - I'm all
ears.
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I'm sure it must be possible to engineer a much better solution.

What about something without the enclosed heat shield but with ceramic coating or something? I wonder how much of the header design (bend radii etc) is dictated by the need to have the heat shield...

I guess it would also need to be something that either did away with these "smog tubes" or had them better integrated into the design (perhaps without welds at all - something like the way O2 sensors are put into the headers).

Bit crap of Ferrari not to sort this out, but I guess by the time failures were becoming readily apparent, the 355 was getting to, or beyond, its production life. So they focussed on the 360 and let the independents sort it.

 

Hi,

First time poster here, but this may shed some light on the exhaust manifold burnout subject. I'm not saying that the following is the cause of any of these incidents, but definitely would have caused problems with my car if left unattended.

About two years ago, after an FCA track event, I noticed that my F355 was running with much more engine bay heat than usual, ran poorly off idle, had a flat note to the exhaust, and also had an unusual whirring sound in the engine compartment. Something was obviously very wrong.

For background, the cats were off the car, the black fiberglass engine heat shield above the muffler had been removed for ease of maintenence, and the exhaust bypass valve safety wired open. The car should have run cooler than the normal OEM configuration.

Investigation proved that the whirring noise was coming from one of two idle mixture compensators. These are silver cylinders one under the aft end of each intake plenum, and are about the size of tomato paste cans, to put an Italian spin on it.

Their function is to port air into the intake manifold so the idle is smoother. Each uses a computer signal to drive a motor which moves a variably stepped vane. The motor is normally restrained by a spirally wound clock spring, so the vane isn't allowed to spin completely in a circle, but fights the spring to position the stepped vane to pass air in several variable cross section steps of the vane. Cutaway photos on request. Since the can edges are rolled to seal them, they are almost impossible to repair.

Problem with my car was that one of these regulators broke the spring, so the motor/ vane assembly just spun unrestrained and thus always passed some amount of bypass air, and made that noticible whirring sound. The idle mixture was always leaner than it had to be, and thus the engine ran very hot at idle speeds.

Has anyone else experienced this?

I'm sure that this condition would have eventually caused an exhaust manifold failure (a burn out) in my car. Aircraft piston engines have a mixure control, and I've seen exhaust system damage occur from just such an overly lean condition (but not at my hands!).

FWIW, Al

 

I'd be interested to see your photos

 

Here you go. The pen point to the broken clockwork spring in the second photo, which let the apeture go uncontrolled, giving a lean mixture and high idle temp.
Al
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I had right and left manifold pipes replaced.The dealers mechanic recommended that I put a ceramic coat on them when my left manifold blew.Now my right blew again and this time I will put the ceramic coating on the right side manifold.I will keep you informed if they blow again with the ceramic coating.

 

I'd like to know how the coating works out, please keep me apprised. I suggest that they coat the **interior** as much as possible as well as the exterior to protect the manifold. Actually, if I had my choice of either/ or, I would go with the interior for the heat protection quality! Lean mixtures run in excess of 1300 F, and that coating will protect metal well above that number.

I had my F335's Tubi coated by Jet Hot in AZ. Since you're in the aircraft engine field, I'm sure that you have heard of them. At the time the shot it, the stainless had oxidized significantly - it had turned a cholocate brown in color. They were able to spray a bit on the interior, but not all of the innards due to the welded construction.

If you haven't as yet selected a vendor to coat, do a Google search on them. I think it ran me about $100 for a media beading and the coating, the round trip shipping was more than that. That coating is holding up very well after 20k miles, including the EGT overheat problem we had discussed.

Best, Al

 

Great info.I will ask them to put ceramic on the inside and outside.I am bringing it in tomorrow morning.

 

Here's a question. If you have new factory replacement headers installed by an authorized dealer, for how long will they warrant the repair? Most manufacturers will warrant replacement parts and repairs for a specific period of time. Don't FNA authorized dealers do this? If so then it sounds like FNA would be eating a lot of headers and thus comming up with an improved version.

 

Regarding the coating applied to the exterior / interior, remember that the coating is effective in several ways.

1) the most important thing is that it will help to protect the **inside** of the exhaust pipe's metal from burnthru from direct contact with the lean (and overheated) exhaust gas flow.

2) it will also protect the exterior of the exhaust pipe assembly from oxidation at the high heats - it keeps it from oxidizing too quickly - it keeps it "purdy". So it obvious that if you had a choice of coating either the inside or outside, you would be ahead with the interior.

Regarding the warranty, see the warranty statement inside of the Owner's Manual. It has been argued that the exhaust system is part of the emissions systems and therefore has a Federally mandated 5 year warranty, but some dealers are deaf but others are easier to deal with than others.

In this position, I'd contact several until I go the results I was looking for; and failing that, go to FNA headquarters in NJ.

This is a chronic problem with Ferrari, I suspect that the idle speed motors I posted shots of recently play a larger part to play in this drama than most suspect.

Hope this helps,
Al

 

The idle air regulator motor(s) takes air from the system down stream from the MAF and bypasses the throttles so that it can regulate the idle speed. This is done to compensate for load caused by the A/C sys, charging sys etc, as well as to provide a higher idle when cold. Since the MAF has primary authority for controlling mixture and in any event all air getting to the cylinders has passed through the MAF the idle air regulators will not have an effect on the fuel mixture.

 

Brian, you are perfectly correct. However, ........

The overheat problem / sour engine was cured by simply replacing the defective idle regulator! **No** other changes were made. Go figure.

To paraphrase an ancient engineering axion: if the observed phenomena doesn't match the theory, then you need a new theory.

This weird problem was discussed with some F mechanics at nauseum, but no one has come up with an obvious explanation. The most plausible theory is that the airflow in the tuned plenum was upset, creating a lean mixture on certain cylinders, maybe degrading into the limp home mode.

Your best guess considered. Al

 

That is an interesting situation then, and not having been able to see it, it is impossible to make an intellegent guess as to why it happened that way. But since those stepper motors have been used on many cars since the intro of the 348 with Bosch 2.7 they have not ever been considered a problem area and failures have been very uncommon. The other issue for me is that while both the 2.7 and 5.2 equipped 355's have those stepper motors, their application, plumbing etc are quite different while the patterns of manifold failure between the versions are the same. I could be wrong but I have seen probably 100 manifolds fail, I have seen 1 stepper motor fail.

 

I was searching the archives and ran into many posts complaining about their F355 headers cracking and some being replaced under emissions warranty and some well... I guess couldn't. It is obvious that these are covered under emissions warranty and manufacturer must replace them at no charge to the owner. There is an 8 year/80K miles warranty on the emissions component mandated by Federal EPA. The headers or exhaust manifolds are emission components and FNA cannot have double standards to honor replacement for some not others... There seem to be something very fishy about all of this.

 

I just recieved my repaired manifolds back from QV in London. They included a burned out tube - thought you'ld be interested.
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OMG, they really blew out!

 

1. When I replaced my OEM CATS with Hyperflows I noticed how dangerously close the T-axle mounting bolt end is to the CAT (almost touches). Bad design the bolt is 3/8 of an inch too long. To solve the problem I undid the bolt and put 3/8 of an inch of washers under the head of the bolt. This made the bolt head flush with the frame at the bottom and the bolt end is now flush with the T-axle fitting and not protruding up to contact the CAT. I now have a nice clearance.

2. When you install the new metal gaskets between the manifold and the head, they tend to fall off the studs (which point downward) in the head before you can get the manifold in place to sandwich them into position. After thinking about this for a half an hour I settled on using Bobby-pins clipped around the studs holding the gaskets from falling off. I put the header on with a couple of threads on a couple of bolts then pulled the Bobby-pins out and the gaskets fell perfectly into place. Worked great!

 

At 34K my 96 355 GTS now has a passenger side manifold leak. The car is totally stock. I can't see any cracks at the attachment points for the air injection tubes but the leak is audible and there is a fine fiberglass "dust" leaking from the right header heat shield.

Plan: QV manifolds with hyperflows on both sides

What are the other parts needed (I'll be pulling the oil tank to ease the right hand header removal)?

Ken

 

You need special wrenches Snap on 13mm - see my earlier post plus 3 very large open end wrenches - 1-7/16 1-11/16 1-13/16 you need to check those sizes to un-hook oil tank lines - Have QV sell you the header gaskets - hold them in place with bobby pins when re-installing the repaired headers.

Good luck

 

Snap-On wrench "FHOM13A" that I bought for $40 on QV's recommendation

 

In the last 6 months since mine failed there have been 3 additional failures on 355s out of probably a dozen cars that I see routenely in the Seattle Area. Counting mine that's 33% - Incredible!!

 

I have a 99 in the shop, 21k miles never seen a track and both are going bad.

 

I have some thoughts and questions that are driven by F355AL observations or theory about the relation on manifold burnout with the air bypass valve. Last summer I replaced my right hand manifold on my '97 355C (OBD1 two air valves). One of the tubes had a hole in it, the two manifolds are the original pieces and the engine has 10000 miles. Before reinstalling manifolds I removed the shielding and had them ceramic coated and did not put shielding back on. When the system was all back together I check the temps of each tube with infared thermometer and was surprised to find that the right manifold was running several hundred degrees higher than the left side. Question 1, why would the right be hotter than the left? I haven't blocked the air valve and rechecked temps but I will. I understand what the stepper valve is there for and that it doesn't control fuel but could they add (malfunction) just enough extra air to heat up the exhaust to the point of excess heat. An engine would still run fine until burnout occurs and apparently the O2 sensor doesn't read out of its perameter. This extra heat could contribute to the engine valve problem also. I do agree that the material used to make the manifold is probably inferiour. Would there be a problem if the exhaust gases were normal temps. My left manifold is the original and is still fine. What do you guys think about this?