I was wondering what's your opinion on this. I can put a "Boroscope" very close to the belt, from the open side of the belt cover and have a very decent and close look at the surface of the belts, in color and relatively high definition. If I could turn the crank slowly with an appropriate wrench, I can inspect the entire belt visually for cracks. Cracks are the main culprit here. No cracks...no imminent belt failure. Wonder if anyone have tried using a Boroscope to inspect belts, without taking the belts out of the engine? thanks.
An old belt with few miles will probably look golden. Takes some pics . Seriously, pick three, five or ten years but any road just change the belts. Peace of mind.
I do failure analysis for a living....belts can't break just because. there must be a small crack, propagating slowly...starts microscopically, then it grows proportionally with miles and rpm, until it accelerates and the remaining ligament is not enough to hold the belt in one piece, and it breaks at that point. I don't buy the theory that a broken belt is "crack-free". It can't be. there must be lots of microscopic cracks and some macroscopic cracks (visible), before a belt fails.
I think the change interval for these belts is very conservative and for a reason because of the enormous catastrophe that occurs when one fails. You seem to be following a philosophy that you're not going to replace it until you see a crack. So when does that first microscopic crack appear, two days after your inspection?
We fly airplanes with a hard to believe number of cracks in its structure.....we run refineries and chemical plants with highly explosive chemicals under pressure and lots and lots of cracks in all the above....trust me...I see them...I inspect them with nondestructive testing...sophisticated stuff.....and we don't replace cracked components until it is necessary.....this science is called "Fitness-for-service"...FFS for shorts...API has standards telling us how much longer one can operate a high pressure...high temperature Reactor with cracks in it.....FAA has similar Standards....but we have to replace a belt with no signs of fissures in it?....don't buy it. If I see cracks just a handful...small...tenths of a millimeter...I will change it immediately...until them belt is fine.
Claudio, you opened with the question. Most of us would suggest changing the belts hopefully so that YOU would not have a catastrophic failure. It's your car and it seems you have made up your mind anyway, so...? Just to let you know, I bought my 308 QV a couple of years ago. It had 27K on the clock. PO showed me receipts for a 30,000 mile Belt Change, Seals, etc. Luckily I did not drive it back from NY to Michigan like I wanted to. When we started the car up here there were some strange noises, an we found a seized Tensioner. Long story short, the belt literally fell off broken as we went to remove it. I thank my lucky stars. Interference heads in a Ferrari are no different from a Porsche 944 or many other makes.m On a 944 maximum for adjustment is 30,000 miles and a replacement suggested for 70,000.
If your mind is made up, why are you asking us for our opinion? Besides, it's your car. If you want to wait to renew the belts after they start cracking, that's your business, correct? You don't need us to validate your opinion of you already are an expert on belt failure analysis.
I put new belts on this past spring after an engine out rebuild. I put on between 10,000 to 11,000 miles since then. I will most likely change the belts before next spring time. I will post what I see, but if someone wants to inspect the 11,000 mile belts. I'll ship them off.
I asked the group if they/you believe I can see small cracks in a belt still installed. I didn't and don't have my mind made up....I just want to see a reason to replacing before replacing...this 5 year replacement rule is bs. A Boroscope would allow for that. 308 owners must have replaced belts here before and looked at them. Or do people just pay the bill and leave? nobody asks to look at the belts? how does it look? If one pays $6k, $8k or $10k for a belt change and other things, I would assume the owner would be interested in looking at the belt before it goes into the trash bin, right? The only thing my mind is made up about is the fact that belts can't simply break without first showing signs of deterioration. Its impossible. My original post is about whether or not we as a group believe that deterioration must happen first, before failure. maybe I wasn't clear.
I would love to inspect your 11,000 miles belt, take pics under the microscope, even measure crack depths (if any) and report to the group as a freeby contribution to improving our knowledge of our cars. I will send you a PM with the physical address of our labs in Texas. thanks
I think you are making a false assumption that a belt failure always originates from a belt fault of some description. You must also consider the contribution of a faulty tensioner. These cars have such a varied use pattern and there are so many other variables. Many barely get started once a year and others are close to daily drivers. Just looking at a belt under a scope really isn't going to tell you everything you need to know to make a rational service decision with regards to this problem.
A belt and tensioners change will not cost 6K on a 308 or 328. And certainly not 8 or 10K. New belts and Hill engineering tensioners are around 200, then add a couple of hours of work and some coolant etc. A good specialist can do (this single) job in less than a day. So 1K and maybe a bit more would be correct. If your clutch is gone or other parts need changing, a service can get very expensive but that has nothing to do with the belts and tensioners. So as in every belt-change thread the same question arises. Will you pay 1K every 3 years to get the belts changed or wait longer and risk a 20K engine rebuild? Your own choice.
Exactly A belt job is about $1000. Every three years that is about a buck a day. Go four if you want but you don't have to drop 5 large every 3 years on this service. I have been doing this for 20 years. Get the belts replaced every three and mostly that is all I will do that trip in.
I've seen more loose belts than ones that actually break. They skip teeth on the pulleys and bang....then all the teeth strip but even then I rarely seen one actually snap. Working on aircraft as you do I can understand your thinking of an inspection, I personally remove my belt covers every year to inspect just to check that all is well. I also actually glance at them every time I check the oil and using a stethoscope I listen to the tensioning bearings to make sure they are nice and smooth. BUT my belts were changed 2 years ago and my checks are only a belt and braces exercise. Sometimes odd things can happen with engines and brand new belts can fail because of say a sprocket drive bearing failure. This happened to a friend, the belts were changed and the sprocket drive bearings had play that wasn't picked up, the belt tracked and shredded....although it didn't actually break. Anyway personally I'd change the belts if they are overdue and then try and casually monitor them which is very easy. All the best Bell
Ok guys, as an impartial observer, apollo specifically states that what he does for a living is failure analysis. Given that, why would you not listen to what he says? If Dr. T said to get a crown on a tooth I would trust him. If Rifledriver says you should change at a particular interval I listen to him. And therein lies the question; Rifledriver says to change at a specific time (At least that's what I remember) because he has seen situations where the belts fail beyond that time and, I assume, that he hasn't done extensive microanalysis of belt failure as there is no need to if you always replace the belts BEFORE the failure happens. If apollo says that you can see, with enough magnification, a belt failing I have no reason to doubt him. However, unless it can be seen with the borescope (His first question) or some other easily available method then it's a not practical for the average Joe and better to err on the side of too much maintenance. Having dealt with some serious factory car guys, they *MAY* test a series of belts to failure then half that length of time/cycle to make damn sure that most folks have a trouble free experience of owning their vehicle. The factory has different goals than you or I.
Like I said, if cracks or any visual cues dictated usable belt life he might have a point. They don't and he doesn't. If it were that simple we would have been doing it all along. I have that equipment too. Totally useless for belts. He might be a doctor but if I have a chest pain I won't be going to the ENT guy. Maybe, just maybe the guys that build them understand what is involved (unlike many here) and suggest a way to avoid problems.Like I said, if cracks or any visual cues dictated usable belt life he might have a point. They don't and he doesn't. If it were that simple we would have been doing it all along. I have that equipment too. Totally useless for belts. And by the way, what are the factory goals? Are they not to protect the reputation of their product by providing information that will give the greatest chance of good service to the owner? If you think its parts or service sales you have a serious disconnect from reality. Only a tiny fraction of a small fraction of the money spent on belts and bearings goes to Ferrari and that expense costs them far more in goodwill than the tiny amount of money that is in it for them. That is the most backward thinking I ever hear. Belts condition is like your health. There is no magic dividing line between good and not good. It is a long term degradation. Belts are exposed to all sorts of dangers and like your immune system they shrug most of it off. Aging slowly destroys that ability. Ferrari has used the experience of the last 40+ years to determine an age at which, in this particular application, they should be changed. No amount of looking at them will change that. If the idea of regular, proactive replacement is unacceptable I suggest getting a different car.
I have never understood the great lengths people will go to in order to avoid a factory recommended procedure on a relatively rare and valuable automobile like a Ferrari 308 which, by the way, also happens to be one of the least expensive belt maintenance Ferraris available to us. Ask Brian what a belt job costs on a 355... Either way, if you have the means to own one of these things you should be able to afford to take care of it. If you cannot afford a belt change every three years, you really cannot afford these cars. If you just don't want to pay to do it that is just neglect. Fortunately the market adjusts for such cars when they are offered for sale.
I had a quick skim through some papers on timing belt failure modes and it seems that most failure is due to fatigue with initiation cracks starting in the cords (at the glass filaments) under normal operating loads. Under excessive loads the initiating cracks start at the tooth roots. "... belt failure is closely related to the distributed stresses causing bending and compression stresses in the cord, and not to the shear stress at the tooth root under normal driving conditions." If you have a borescope, see if you can see the date codes. If they are old, change them.
Besides the cars owned by itinerant bums that sit for years and years with belt failures due to age, my recollection was there are many failures due to other factors such as tensioner bearing failures, air pump failures or other cam related issues. It's not just the belts.
Derek that is correct. The problem come from the broken or weakened cord. Caused by stress or bending over the normal operating radius bent which break them. This can happen because of many factors. For exemple a loose belt will be driven on the tip of the tooth instead of the root which pull and bend the belt under load past the working radius. I own a cog belt main rotor driven helicopter and you want to KNOW THIS. Brand new kevlar belts broken after less than 50hrs use sent back to manufacturer for analysis and that was the answer. Broken cords due to ratcheting and incorrect theet load.
I once strechted my luck to 9 years on my 308. Belts looked perfect, but tensioner bearings were dead. My luck was probably very close the the end. Like other said, two belts and two bearings is cheap and time to do it is not much. 5 years is my standard. And BTW the one on my copter is 5 years or 500hrs and cost $500. WHICH IS STILL CHEAP. Compared to life.
