Are belts for 355's (V8's) now not Kevlar reinforced?
Good question but I auusme they are if you buy them now. If not you can get them for just about everything.
Has anyone ran a Reliability Analysis on the cam belt failure similar to what we did on the Testarossa Differential? It's a long thread but the crunching starts about here... http://www.ferrarichat.com/forum/boxers-tr-m/523391-testarossa-dreaded-differential-issues-questions-7.html It would definitely take this thread down a more scientific path rather than speculation. I'm happy to run the numbers if someone can collect the data. I would suggest the following: -Amount of vehicles with cam belts produced? -How many have failed? -What was the milage at failure? -What was the age between belt changes? -How many have been replaced without failure, their milage and belt age? If the data is useable, then our model will calculate the following: -Probability of failure by milage -Probability of failure by belt age -Survivability rate without a belt change -Hazard rate not changing the belt. PS. I must admit, I too am leaning on the side of caution having a TR. Just like the diff, I was not convinced until the numbers came back.
If you were going down that path ..Need average miles a trip and location/temp .. I would imagine rubber likes a cooler temps and run regularly vs 200 miles in one trip and put away etc ..Just my two cents Sent from my Moto G (4) using Tapatalk
The problem with this is that it becomes assumed that it is the belt itself that is the root cause of the failure, rather than a casualty in a sequence of failures caused by... a pulley bearing, or a drive sprocket shaft bearing, or foreign object introduced to the belt path, and so on.
Jim- No, actually I did not. All the V12s produced after the belt change did go to 5 years. I never mentioned the 456s and 550 except to say the new belts replaced the old ones on those models at the same time. So tell me what I said that was wrong after you reread it. Need to work on your comprehension skills. The belts are the same and the belt runs are the same on the 456, 456M, 550, 575, and 612. The only difference is a tensioner bracket fitted to early 456s and very early 550s that was updated well before the new belts came out. Most shops and owners now use the 5 year interval for the earlier V12s, despite what the bulletin says, and fit the updated brackets on early models.
If FChat were to block the posts containing the word belt, I wonder how many posts would disappear..............
I understand that there are many factors that affect the belt reliability. I bought a TR that sat around for 10 years. Belts looked fine in regard to aesthetic appearance (no dry rot, tears, missing teeth etc) but the tensioner bearings fell apart upon removal. Is this therefore a belt integrity issue or a bearing issue? In other words, should Ferrari be more concerned about components other than just the belt? If I were a belt supplier, I would strongly argue this point if the belt was NOT in fact the weakest link. I hear ya. Just like the TR differential, root cause was less of a concern than the reliability or probability of catastrophic failure. We all knew it was the weld that broke (Failure Mode), how that was caused was still open for debate. I think we have the same issue here. We can all argue over what causes the catastrophic cam system failure (valves punch through pistons), but what is the probability of that Failure Mode occurring regardless of how it's caused?
OMG, the horror. Yet some here continually ridicule others for going beyond the edict of the factory. LOL
I'll give some data. Bought car in 93 and changed belts then just because.Between 93 and 98 changed belts at 5yrs. After that have been on a 6-8 year interval. What I can say is by my second change there was a rumble at idle which I took to mean the tensioner bearings were going. I think these should be done every belt change. There is a big difference between just changing belts and doing everything else the belt touches. I also do visual on belts each spring and on a Bb you can look at the belt teeth. Each time a belt has come out we have turned it inside out to see if there was cracking running in from the teeth, never saw it. A flat cammed BBi will be easier on a belt than a 4 valve TR, and a 8k rpm single belt v8 is harder still.. A car that sits allows the belts to set which is an aggravating factor. Time and mileage are two co factors and bearings are probably the greatest single factor inside of 5-10 years. I am going to say that on the older 2 valve cars tensioner bearings pulleys etc are probably the single leading cause of failure, exess belt interval time being the second.
Whats the recomended coolant that alsts longer. leno likes Evans but I hear it does not cool so well. On another note anybody run a Lipo battery? Big weight savings.
I've said it prior, IMO, it's risk management. As an example, let's say that one follows the 3 year recommendation for a 355 and the estimated cost is $7K per major (yes, I know it can vary) In a 15 year period, that would be 5 services and a total of $35K Doing every 5 years would be 3 services and a total of $21K. I'll personally roll the dice and keep the surplus $14K in my pocket and should a break happen, that will cover it. Push to 7 years and the *****potential***** savings may be greater. I'm a believer in 5 years but I'm too busy to get to my car this year and I already have another in pieces so I'm going to push to 6 and I'm not worried
I will just say that I had a belt failure on a Boxer. I can blame myself for an overly aggressive downshift. So, learned the hard way not to go overboard on downshifts.
Thread starter here. I don't log in for a week and WOW. For all the grief I got early in the thread I'm glad I did it. After reading some of the other belt threads I've come to several conclusion. Despite the suggested 3 year interval, it looks like most are on a 3 to 5 year cycle. And you can't sell a belted car without 1. recent belt service or 2. allow for a belt service discount. Both not unreasonable. The weak link is not usually the belt. Unfortunately close inspection of the tensioners and all ain't that easy. Here's a theoretical question for someone with actuarial background. An insurance policy for belt related failure. What would you pay yearly if you could buy a policy to cover belt related failures pushing the service interval to 7 or 8 years? X number of belted car owners pay X per year for a policy to cover repairs if a failure occurs with in 7 years. Dumb idea?
No such thing as a downshift related belt failure. BBLM's were raced very aggressively with exactly the same belts as the street cars. 308's with the same belt and drive system have been run to 10,000 rpm. 355 with nearly the same system was designed for 10,000 rpm. Sorry but that was someone's fantasy.
Coincidental? I saw 10,000 rpm a time or two on a missed shift, no problem. Sounds plausible to me that a really fast/aggressive change in belt speed could accelerate a belt faster than the cams could follow. Or, crank speed changes faster than belt teeth are willing to go. AC and music masked sounds of the actual event. A witness at the downshift location stated it sounded awful. Parked a minute later and then would not start.
Faster that the cams could follow? Do you have any idea how many race motors including decades of F1 motors had belts and yet yours is the only known case in the history of Gilmer belts. I don't think so. Sorry but it was just a case of a bad diagnosis. The belt may have jumped time, that I don't doubt. It may have even done it at a hard downshift but that was not the underlying cause. If they were that unreliable the sides of the road would be littered with cars with bent valves.
