The 355-Exposed? Covered Up? or Overlooked ????

Upon reviewing Jays' data for the 355 I am quiet perplexed to say the least.

First: I have never seen a valve guide composition like this. It is unlike all the others tested, including the 330 which is another breed of animal all together. The inclusion/exclusion of elements along with even the smallest changes in percentages have an effect on the material properties at the molecular level. Even if 2 materials have the same percentage of elements, they can turn out differently depending upon quality control in manufacturing, and the process used to form the final product. Even though the 355 guide is harder than the others, hardness alone is not a true indicator of its' wear resistance. Relying on hardness without understanding the microstructure of the material is a risky way of determining abrasive wear.

Second: I do not know what I am looking at without Ferrari's data. In other words, is this the recipe they specified, or is it an improperly mixed batch from the manufacturer.


Further data from Dave indicates a condition in which severe overheating of the valves occured, which is most always caused by insufficient contact area at valve/seat(not cracked headersd as most believe). Whether this was an existing condtion due to assembly when new, or became that way as a result of valve guide wear, I cannot determine. It is also apparent that the stem seals completely failed due to the excessve guide wear.

I will say this. A leaking intake valve starts a chain of events which can lead to major problems that effect the remaining cylinders, and the intake and exhaust systems. Super hot air blowing back into the intake(because of the radical 355 cam overlap), which the other cylinders injest. If this condition goes on the guide wears to the point that the stem seal looses control of the oiling and oil gets into the combustion chamber. When the seal goes it allows unmetered air to be sucked into(engines with VE less than 100%) the cylinders which upsets the AFR.
This super heated reverse air flow heats not only the intake air in the plenum, but fuel and fuel injectors, the whole throttle body for that bank of cylinders, and any sensors within the immediate area of the intake proper. Upon further failure of seals at int/exh the headers, cats, and O2 sensors go.

IMO, if Jays data is what Ferrari or their suppliers specified, it was a bad choice. This kind of valve guide material can survive, but ONLY if the installation/assembly of seats,guides,valves,tappets,cams, are near perfect.

Given the fact that Ferraris' history of poor quality control and assembly techniques, coupled with this type of valve guide recipe, could be "why some do and some don't" fail.
If a worker gets it right one day then it will last....but if they become laxadasical the next day then it is doomed to premature failure.


Are ALL PRE 1998 cars valve guides "bad", as most say??? Well, yes and no. This guide is good for heat dissapation, but a poor choice when you look at the valve stem size(more like a tooth pick), high revs,Ferrari's 1st attempt at a 5valve(radial intake valves) head with its' complex geometry, and a corresponding lack of correct head assembly procedures. Even the valve stem seals may be a contributing factor also.

Instead of improving quality control in the assembly process, I believe Ferrari (at that point in time) elected to go with a sintered iron guide that could take the side loading caused by errors(among other things)in the valve train. This has apparently been carried over to the 360/430 V8's as well.

Are sintered "iron" guides bad also?? I have no problem at all with Hitachi Powdered Metals Companys' newest formulation...BTW theirs is not "iron". This newest PM guide can run at almost no clearance, has good heat dissapation, can run almost dry without galling(which leads to seizure), and has an expansion rate more inline with the aluminum alloy head material. I am not sure of how brittle it is, but it is far less than the "iron" guide Ferrari uses.

 

Ferrari has switched all valve guides 355-360-430-Enzo to the same sintered "iron". Guide problems for the most part were limited to the copper alloy.......that is why they switched to the PM ones in the first place. Also, from what I understand they updated the production facility, to the extent this has eliminated any quality control issues I have no way of knowing.

360 has 5 valve heads(2 exh. inline with the cams' shaft, and 3 int(same radial array as 355)-1 inline with the cams' shaft and 2 at an offset angle). By using a "pentroof type" cylinder head Ferrari could drop back to a 4 valve set-up for the 430 series.

I do not as of yet have a vendor for the Hitachi ones. Yes, they do have good machineability.


You still can't go wrong with the Manganese Bronze(they should have called this a Zinc Bronze..lol).......it is hard to beat for the price.

 

Well it's been awhile, and believe me, when you think it's safe to go back into the water..WATCHOUT!!

If anyone is still interested in this thread I want to put some stuff here for your consideration,review, and comments.

Since this thread has already gone WAY BEYOND any other thread on this topic, I thought I would take it a little further and go right to the "Black Hole".

Dave Helms and I have been kicking around this exhaust reversion thingy....and it appears to be alive and kicking back..lol

There was a post a month or two ago that said the Jet-Hot coating was delaminating on the exterior of the header. My first thoughts were that if it is coming off the exterior then the interior coating is most assureadly flaking off also.....and if it is flaking off inside then because of the Tsunami exhaust reversion wave produced by the 355 engine it is definitely going to wind up in the cylinder.

Talking some more with Dave, he had taken a scope and looked inside several sets of stock OEM headers and said that there was considerable erosion of the header material noticed. Hmmmmm, so now we are looking at tiny parts of header metallic material that may be getting caught in the reversion wave and getting into the cylinder.

I remember many many years ago when I was doing engine dyno testing on a SBF Ford motor. The engine was in perfect condition(completely rebuilt and bench tested).
I kept it on the dyno for 2 weeks and ran it a total of 8hrs per day(including weekends) trying to get reliability and wear data.

The cams were radical(overlap) very similar to the 355, and we were running an exhaust set-up fabricated from mild steel.


Here is an old pic of what the intake manifold looked like at the end of the test:
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Here is a pic of the inlet bowl
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Do you see anything of importance in these 2 pics????????????????

 

Thank you John,Oz,and 355 for your comments.

What you are seeing in the pics is the result of the exhaust reversion wave. The intake bowl looks like the exhaust bowl, and the intake manifold runner looks like an exhaust port. This was a fully prepared race engine,i.e. the valves,seats,guides,and valve train were in perfect condition,with absolutely NO issues.

Just imagine....what should have gone out the exhaust pipe wound all the way up into the intake manifold. WOW!!!!!

Well if that isn't bad enough it gets worser(as my daughter would say). After disassembly, the parts underwent microscopic inspection and chemical analysis.
There were microscopic poc/pit marks, not only in the cylinder head and piston crown, but even more amazingly the intake bowl,intake manifold runner, and the exposed portion of the valve guide.

What was this pitting from?? Remember the exhaust that was fabricated from mild steel? The results of the chemical analysis identified exhaust system metal in the cylinder head,piston crown,intake bowl,intake runner,and the exposed portion of the valve guide. These metal particles were not from some catastrophic exhaust failure....it was from the normal erosion process of the metal caused by the superheated exhaust gas(fluid) passing thru the piping at high velocity.

Now you must also consider that not all of this eroded header material got imbedded into the upstream parts.....some went downstream. Hmmm, is that where the cats,O2 sensors,and thermocouple are located?

So now we got a 3 ring circus goin on here:

Huge Exhaust Reversion Wave

Degradation of Exhaust System

And Burnt Fuel By-Products in The Intake Manifold



Does anyone see how great the circus is?? Barnum & Bailey never had such a freak show..lol

 

Please understand this, the pics and evaluation were NOT done on a F355. However, this reversion wave does exist in varying magnitudes, whether it's a 355,348,360,etc. It is not limited to Ferrari. As a matter of fact all car mfgs,all models,motorcycles,etc........I'll go so far as to say any 4 stroke(maybe even 2 stroke??) internal combustion have to address this dynamic.

What I posted shows:

1. There is factual evidence which proves the existance of an exhaust reversion wave. This reversion wave can be of such magnitude(overlap just opens the door for the exhaust system produced wave) so as to cause exhaust to be forced all the way up into the intake system. To what extent a reversion wave of this magnitude can effect everything upstream of the exhaust port(piston,cly.liner,valve,seat,guide,FI,and intake sensors) is yet undetermined.

2. Any erosion of the exhaust system within close proximity to the exhaust port can in fact cause the upstream parts to be contaminated. To what extent this contamination effects the reliabilty,functionality, or wearability of upstream components is yet undertermined.

3. The introduction of super heated burnt fuel by-products back into the intake system and cylinder combustion area will cause a decrease in combustion efficiency and VE(volumetric efficiency). To what degree this effects AFR, and the EMS's ability to ascertain and compensate for these events, is undetermined.

4. If the exhaust reversion wave is of a sufficient magnitude, ambient air can be drawn-in/introduced into the exhaust system. This is especially significant where 2 exhaust pathways are available,e.g. the street version 355 by-pass exhaust system. To what degree this effects the O2 sensors and thermocouples as outside air is drawn back into the highly restrictive primary exhaust system(when by-pass opens-the least restictive) is undetermined.


How do we go about determining the "degree of effect" these concerns actually pose for the 355? Then how do we address these issues so as to minimize their effect on performance and reliability?

 

Yes Oz!!! The reversion wave magnitude does vary with rpm. The primary pipe diameter and lenght contribute significantly in the production of the reversion wave.

F1 has used stepped headers. Is this necessarily the way to go on a restrictive street exhaust which has a max rpm under 9,000rpm??
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One of the concerns listed above(exhaust material/erosion contamination) is very easy to solve.

1. If you are not using ss,(e.g.mild steel,or a low grade mild steel alloy)....apply a PROPER(one which can take the corrosive, high-temp,high velocity exhaust without delaminating) coating to the inside of piping.

2. Use 304 or 321 ss, or the more exotic inconel or titanium if weight is a concern and higher egt's warrant.

 

Sorry, but I neither have the time or patience to get into this.

It would be a reasonable assumption that ANSA used 409ss,but I just don't know what the oem headers are made of.

409ss is only a little better than carbon steel...it's a Group 1 ferritic grade commonly used now days for exhaust systems. Heat and friction are always the biggest causes for corrosion. Heat alone, will thermally fatigue 409ss to the point that it will start to oxidize and fall apart. Fatigue/oxidation is a problem caused by cyclical temperatures and hot gas impingment. Other factors that may contribute to this degredation are embrittlement by "phase formation" and "grain coarsening" at high temperatures, or even intergranular corrosion. I just don't all the processes involved in the 355 header degredation.


NOTE: Do not pull your 10,000mile headers off and have them coated.....the time to do the coating is when the headers are new.

Don't let all of this bog you down. The headers are degrading, by what ever processes. The size of the metal particles which are being released during this degredation are unknown at this point. The degredation appears to be the worst at localized hot-spots. Hopefully Dave Helms will jump in here, as for now he is the only one who has factual data on the 355.

Two things we know for sure:

1. The oem header metal is degrading. The particles release during the degredation process have to go somewhere. WHERE they go and what this all means is yet to be determined.

2. We cannot alter the source which is causing this degredation,i.e. the engine. So we are going to have to control this exhaust system degredation thru coatings, or wholesale replacement of exhaust with a metal that can properly handle what the engine is dishing out.