Possible cause/relief for header/valve guide problems???

Interesting observation, I'm sure a cooler engine bay will help reduce wear and temp related breakdown of many items, however I have very little belief that the valve operating in its correct manor will cause damage to the engine.

I personally believe that using a car for extended periods or at high RPM with leaking headers is the cause of the valve guide problem, the leaking header causes the engine to run lean due to the o2 sensors getting an incorrect reading and the ECU adapting the fuel/air to match this false reading. A lean running engine will soon damage the softer bronze valve guides.

There has been plenty of debate on this here already, but in the interest of development I think its about time we debated this topic again, we have some very knowledgeable people on this forum, there updated input would be good to hear.

 

I agree in a way but I think it may be the way you are looking at it. The valve is not there to back up exhaust gas, its there to control the path of the exhaust gas and direct it through the silencer or allow it to flow more freely through a smaller part of the silencer. The build up of heat is a direct result of the restricted path through the muffler, no question about that, but the build up of heat needed to cause damage to bronze valve guides would damage far more than just the guides. In effect what you are saying is that the oil is no longer able to cool the engine due to high exhaust temps. Part of the function of the oil is to act as a heat transfer which is why we have oil coolers fitted to our cars. If the oil was getting to the point of not being able to cool the guides then there would be other parts of the engine that will suffer.

Its a good thing that it brings down the engine bay temps. Why do you believe it will reduce the risk of wear on the valve guides?

 

Good observation - to add a bit more substance it'd be great to have some actual temps. Maybe I'll give it a shot if I get a chance.

The only counterpoint is that at idle / low speed operation there isn't as much heat being generated (while the valve is closed). When the extreme heat is being generated the valve is open. Could this point to valves that don't open causing most problems? I'd believe that.

 

Reducing the exhaust temp will definitely improve the life of the OEM headers. Have you seen photos of failed headers? They look like someone took a gas torch to them, melted.

I might try wiring my valve open just to see/feel the difference myself. My car is already very loud so I don't think I will leave it wired open but it would be good to have some first hand experience in this.

I'm all for reducing the engine bay temps. On that note, the temp dropped in the engine bay when I removed the cats, not that substantial, but a small difference.

Did you notice a difference in the oil and water temps?

 

Another topic that has been talked to death but just suffice to say you are really barking up the wrong tree. With it wired open under some operating modes there is actually exhaust reversion. In other words air going back upstream through one of the underutilized pipes causing the cats to cool, and the O2's to get a false O2 signal enriching the mixture. That is why it seems cooler. There are a whole bunch of other, destructive side effects going on as well but I really don't have the time, i have to go home.

Lets just leave it this way. Once you have shown that you have more experience in automotive engineering than the collective ability at Ferrari and have a few F1 championships under your belt give reengineering their cars a whack. They really are a pretty smart bunch of guys.

 

I was hoping you would stop by Brian, thank you.

Has your opinion of this topic changed in recent times? If I remember correctly you feel its the make of of the metal used to construct the guides that causes the problem? (I may be confused on this one, sorry if I am)

 

I would always defer to the experience of experts like Brian, Dave Helms, etc. I thought I had read somewhere why it's bad to wire open the valve but couldn't recall the details. Thanks!

However as for the Ferrari engineers, no doubt they're bright people with great race experience. But they too are on a limited budget with limited development time. Aren't they the same lot that designed and produced 355 headers that burn through, valve guides that wear, etc.? We're not smarter, we just have the benefit of hind sight and collectively millions of miles of development experience.

 

+1000 ...................... though not as bad, the 360, 430 and 550 have seen a few 'bad headers' as well ..........

 

As bright as those guys at Ferrari are/were, we have found all sorts of stuff they could have done better on our 348's which we have corrected for the better. I am always looking for a better solution than compromises that the engineers may have had to make to get the car doone on time, on budget and satisfying the myriad of requirements and regulations of the various world markets the cars were sold in.

If you say, Brian, that wiring the valve open is generally bad and destructive in the long term, I'll take it. Claiming that the Ferrari designers and engineers got it right the first time out, well, that's a stretch.

 

The valve guides and the headers are not design failures. They are substandard materials supplied in the form of finished products by outside vendors. That is not to excuse Ferrari as an auto manufacturer for using them. I suspect that problem has a lot to do with problems, even corruption in the procurement department. I do see it as seperate from design work.

It is really too bad. The vast majority of the design work is very good, almost to the nut and bolt the parts built in house are outstanding, some of the best there is but when it comes time to buy parts outside they allow junk through the door.

 

The 348 was designed by an almost entirely new, fresh out of school bunch of designers with almost no practical experience. Most the the prior engineering staff had been hired away by the most recent buyer of Lamborghini. I believe it was Chrysler at the time but new owners at Lambo were coming so fast and furious in those days it might not have been them. Anyway Ferrari had to go out and find a bunch of warm bodies fast.

Haven't you ever wondered why suddenly after so many years of Rube Goldberg engineering Lambo suddenly started to build some pretty good cars around that time?

 

Careful there, Ferrari use plenty of the technology they develop in F1 on their road cars, it takes time for it to filter through, you wont see the latest technology in the road cars, but it gets there eventually.

 

Very true James !! Especially the 355's individual throttle bodies, five valves per cylinder and header exhaust manifolds to name a few ...... ....... unfortunately cats and dual path exhaust/mufflers are a product of emissions/noise requirements .

 

my valve guides wore at 20,000km without leaking headers or the use of O2 sensors (My car has MoTec)

Being a challenge (street registered) it doesn't have the by-pass valve at all.

 

OK, Interesting. What do you believe the cause of your guide failure was? Are you still on original OEM headers?

 

His being a challange I am assuming its been raced and seen 8500RPMS for extended periods.

Not to kill the subject excuse my ignorance but what percentage that are "not raced" with good headers have had valve issues?

 

Mine was one of them ...... the valve guide holes pretty much just elongated/deformed causing slop, thus the valves not able to 'seat' properly. The headers were and still are leak free ........... cats were replaced with hypers at that time as well.

 

Crap valve guides just like all the others.

 

Been asked a thousand times. There is no data base and building one will be next to impossible.

 

Bad metallurgy (bronze alloy), plus tiny valve stems and guides compared to 4 valve heads(less space on 5 valve heads)...any distortion of the narrow valve guide will disrupt the seating position of the valve due to the relatively narrow(and weaker) valve stem...who knows what the metallurgist was thinking when he used American pennies in place of straight copper(which have never been pure copper since the early 80's)...recession proof ferraris? I don't think so

What's the root cause for the distortion of the valve guides? Perhaps they got too hot. How? A valve gets hot and transfers heat from its face to the valve seat. Since the valve and valve seat are no longer touching, due to vibration in the the puny valve stem, the valve face now cools itself through the valve guides, which don't typically get as hot. Bad bronze freaks out and distorts. Help the exhaust heat escape the combustion chamber quicker, and no more problems. I commend the OP.

Infamously, on modern low emissions Camrys, by running the engines hotter, the oil would sludge -- an example of high temperature effects on untested materials(in this case oil heat transfer through aluminum alloy), all in the name of lower emissions.

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