Maybe we should all chip in, buy a motor, put new belts in it, run it on a bench (with 2 week idle intervals) until failure.
The "conforming of the belt" to its static position for extended periods of time, makes a lot of sense to me, and it seems that it would put your car at risk if you don't drive it frequently. Here in the frozen north, tires flatspot very quickly and thump for the first couple of miles. Same principle. Come spring, it would would seem to make sense to rotate your engine slightly in warm conditions before you fired it up and stretch out those hardened bends.
Dear Comrade barabus, The TR is to have the belts changed in March and the number of years that will have elapsed will be four and a half. It seems that many feel comfortable with five years so this is what I shall continue to do. All good wishes and by the way, the Garman is working well. With kind regards, 512 Tea Are
I am still trying to understand the point of this thread. What theory is trying to be proven this time? Dave
The only constant seems to be that preventative maintenance should be determined by ones "feelings" and if that doesn't work out for you someone else should pay the price ;^O
Now I understand. Cant say I agree with the new thought process but to each his own, I could care less how often they get replaced. The next arguement will be how expensive they are to fix when the change interval is at 10 years and major failure rates go from single digits to mid double digits. Back in the 70's and 80's there were folks that owned the Fiat 128's / X1/9's / 124's that bought spare heads and just changed everything out when the belts broke, valves were about $4.00 each for those. There are very few instances where belts break with no outside influances. I have posted many photos on here of debris worn into the cam gears causing an extreemly high rate of wear of the belt. Daniel posted these for me a year or 2 back. No one in their right mind can debate weather or not these belts should have been changed at the 5 year mark. I would bet that 1 in 10 here could tell me what the tension settings were on the belts they last installed was, either Sonic or Steager yet it is said they are OK. How do you know? Were the belts over tensioned causing extreeme sideload on the drive gear bearings and tensioner bearings causing overheating of those? Under-tensioned causing flapping under a given RPM? Take the time to watch these belts under varried RPM's with a flashlight next time you have a view of them. Even properly tensioned belts flap around at a certain RPM's and the sight will scare the hell out of you. Its OK, they do this but it sure makes one question if everything is in proper order and as good as it can be. Daniel gave a good example but with it follows many other questions. Why was there a side load on the gear fences, there shouldnt be? Did someone in its past install the idler bearing with a 3 pounder rather than heat shrink it in place properly? It only takes a half a degree tilt in that bearing to throw everything off wack and I have removed many that brought a sliver of aluminum out with them due to an improper install the last time. Was a proper square ended puller extension used with the bearing puller or someones 3/8 ratchet extension and the bearing came out crooked changing forever the way it will seat when replaced? I see rust so thick on the cam and drive gears it could be described as furry and the rubber belts have to work in this enviroment. Mix that with a little oil from a seaping / weaping (not leaking) cam seal and one has a good lapping compound. One only has to look at the wear on a cam gear to understand what is going on here. You think the rubber belt riding on a steel gear alone caused this wear? I have yet to find the so called Mechanics Lobby spoken of earlier (OP) but I answer my customers questions when asked my opinion. Paul stated it correctly earlier in this thread, most never hear about the major failures or for that matter the REAL reason behind the failures. Again I would venture to bet 90% of these have little to nothing to do with a belt alone failing. There is a world of stuff going on with the engine, replacing a rubber belt is only a minor part / reason for doing the job in my opinion. Dave
Up until now, I have refrained from joining in on these (many) belt replacement discussions. But now (slightly off topic) I guess I'm wondering why they design these engines with the interference in the first place. It's obviously possible to do design and produce a noninterference engine. Does it have to do with the level of engine performance? Are there high performance engines out there that don't interfere? Just wondering... - Eric
I understand it to be difficult to maintain the correct bore/stroke, the compression ratio, and enough valve circumference and lift for good breathing without the so-called interference. Briggs & Stratton, maybe it doesn't matter, but Ferrari is different.
That's probably part of it but I know there were older Ford Escorts, as an example, that had interference engines yet they were very standard engines... I mean low/medium power output. Later they went to a non-interference engine. Many different brands have interference engines. My 2.5L V-6 Saab (quad-cam) has an interference engine and the new style timing belts/cam sprockets. They still had failures mostly due to poor tensioner design and lousy bearings. Many engines were destroyed and Saab reduced the belt and bearings change interval down to 30,000 miles (with the new style belts!). Sounds Ferrari-ish doesn't it? Saab dropped the engine after two years but it was also used in some other brands/models including the Cadillac Catera (in 3.0L form). Made for some very unhappy Cadillac owners (considered a premium brand) with the engine failures and the requirement to change the belt etc. every 30,000 miles. The belts on mine have been changed 3 times in 135,000 miles. No problems so far. I did the last change (first time) and it was very complicated and very time consuming and I had to buy a $300 special tool kit to do it. Ferrari belts change was much more straightforward.
There you have it in a nut shell. Run your belts and other parts as long as you want to. Keep a close eye on bearings, belts, and gears and if your lucky you can go for as long as you feel comfortable. If not you pay the piper. Through complete ignorance I made it 14 years on a set of belts. Only 1000 miles put on the car in that time frame. I guess I lucked out.
Well, why buy insurance? You don't need it until you have an accident. I had a Porsche 944S, if that thing went far over 45,000 miles it was rolling the dice. 280,000 miles when I sold it, 6 or 7 belt changes definitely cost less than a cylinder head would have.
I see an average of two a year. Generally 4-5 years old or have had timing belts replaced put ignored checking the tensioner, pullys, seals are all in good condition and are going to last another three years. Many reasons there is such a big variation in costs to service timing belts. Just throw a set of belts on or do it properly, tensioner bearings, seals, update inferior or revised components and proper degree in the camshafts.
Yes. A Mondial QV that I'm personally familiar with had a belt failure. The date code on the belt revealed that it was 7+ years old and had 25,000 miles on it. No other parts of the belt drive system were in question, and most of the valves were bent. It happened during a moderate acceleration at mid-rpm. I have one of the souvenir valves in my garage.
2 512 BB TMU/both 76 & 78 1 512 BBi 3750 miles 1982 1 TR-86 13k miles 1986 1 355-9600 miles 1995 1 355-2200- miles 1998 1 348 T-Cab 14k+ miles 1991 1 91 F-40 4400 miles 1991 1 308 Glass B-drysumper 17,000Kms P-6 cams stock 1975 1 308 GT/4 HOT motor 33,000 miles 1974 The failures: what is consistent was at downshifting, or, cold start up after a period of sitting, sometimes a long period of sitting. Conformity of belt to its parked position a likely factor. Most cars had been on a 30k major service interval of 4 years-no more! There was-frequently-rubber welded to the drive cogs, from rust lines on these drive cogs, IMHO as a result of sweating/comdensate after running hard and being put away wet. Obvious tearing at start up....a hard downshift would cause it to skip a beat... go booom???? Also, some odd rust here and there as a result of water from "detailers" In general, these were weel heeled owners who were not cheap. The cars were well maintained-belts and tensiomers were ALWAYS accquired from FNA-in ALL cases. They break-we use Staeger's before most had heard what they were. Same with drive bearing replacements in QVs etc in early 1980s...these are infrequent occurrances. Rare, but these do stick out in my memory.
I'm another case study. The forward bank belt in my Mondial QV failed a few years ago. Ended up replacing a whole bank of valves and all of the valve guides on both banks (since it was apart anyway). FWIW, these belts do not "break". Rather, the teeth shear off. Mine failed at the drive gear-belt pulley. That is a small diameter pulley so the belt flex is great. About 10 teeth sheared off leaving the belt stationary while the pulley rotated. I was driving straight and level at about 3000rpm. I saved the belt and will try to get you a picture of the failed zone. Upon close examination, it is a wonder that the failure didn't happen sooner as the edges of many teeth were beginning to tear loose. The failure was in about 2000. I had owned the car for about 1 week, fully planning to R&R the belts but alas, driving was too fun. I wrote a $9000 check to FoH that year.
I, personally, had a cam belt failure. So yes, they do happen. I had a tensioner bearing let go and there are pictures on this forum of it. I had 11k miles and 6 years on the belt. The belt did not break or malfunction though, it was the tensioner bearing. As for a noise, I was not in the car when it happened ( a mistake I will never make again...so I don't know if the bearing was making noise)...I know that I had a whining noise that I could never diagnose and asked for help many times on fchat...It would only happen upon hard accerlation at low RPM though...once RPMs reached over 2500-3000, the noise would go away...if I let off the throttle, the noise would go away...I don't know if that was the bearing failing, and if someone thinks that sounds like a symptom...please let me know so that I have that knowledge for future reference....however, when I dislcosed that issue, nobody offered that up as a possible reason...Anyway, it does happen...I have personally felt the sting!
