| Author | Message | ||
| Edward Gault (Irfgt)
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One good thing about the HTD belts is that they run on very low tension versus the square tooth belts. This was incorporated into my design so that the factory tensioner utilizes the extreme beginning of the tensioning process which necessitated the idler/tensioner pulley being designed to the exact right size and the necessity to slightly modify the rear belt dust cover. All this was designed to lessen the tension on the belt and bearings and lead to a longer life for everything. | ||
| Paul Sloan (Sloan83qv)
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Timing case cover houses crank seal,oil pump and cam drive gears and seals. The case sits right below the waterpump, it should not be be confused with timing belt covers. | ||
| Greg Rodgers (Joechristmas)
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! | ||
| Paul Sloan (Sloan83qv)
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Here is a warning regarding this discussion, I am into my second straight week of pulling my 308QV engine and splitting the cases because one of my belts was OVER TENSIONED when it was installed by an Authorized Ferrari Dealership 12,000 miles ago. The damage that occured was to the cam drive bearing (lower sprocket) and seal, I was doing 80 mph and in the process of overtaking a slower car when in my rearview mirror I see a cloud of white spoke comming out the engine vent slats (oil being pumped out the seal and onto the exhaust pipe). I was actually able to nurse car home (performing moosquito control at the same time) and began the process of removing engine. On a 308 QV you cannot remove the front timming cover without seperating the block from the sump. So take my advice no matter what belt you have or who put it in CHECK and AJUST YOUR BELTS or prepare your engine hoist or your wallet. I expect to be back on the road next Saturday after 15 straight 7hr days working on this car and some people go to Disney for their Vacation! | ||
| Dave L (Davel)
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Lotus has the 100k belt as well, since about 95 its the only belt they sell. They recomm 5 yr replacement or 100k but we know the valves need some attention before 100k, so why not put a belt on when its all apart. Same for a Ferrari. Its cheap insurance and it allows you to look at the tensioners etc and make new or adjust as necessary. We all seem to be hung up on the belt change as a pain in the ass, but in a practical sense you will be disassembling the valve train for some adjustments anyway. And who is driving the cars 30k a year and needing an expensive service anyway? I think the hobby and mechanics have us convinced we are all living in a world where our precious exotics are just waiting to fail, so we best service the living daylights out of em or else. Lets be reasonable...drive em..service when necessary on schedule or if something minor fails(waterpump etc). I think we need to give ourselves a little more credit and give our cars more respect for the fairly well engineered machines that they are...JHMO...Dave | ||
| Edward Gault (Irfgt)
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What I am telling you is that the square tooth belt, if your car is so equipped should last at least as long as the owners manual says to and if not I would sue them from now on. If your were converted to the newer HTD {round tooth} HSN {highly saturated nitril} belts and a dependable idler/tensioner, then 100,000 mile belt changes would be in order. I do not ever to expect to ever have to replace the belts on my car again as I doubt that I willl ever drive my car that much, and the age of the belts does not seem to have a bearing on their longevity. Still don't believe me, then read this article below.   | ||
| Frank Parker (Parkerfe)
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Herbert, So can these type belts be used in a Ferrari such as my 348 ? And, are you telling us that if we used one we could go 51,500 miles between belt changes safely ? That's what the Ferrari owner's manual says my 348 belt change interval is. If so where can I find one and what size do I need ? | ||
| Herbert Edward Gault (Irfgt)
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What you have been lead to believe is what they wanted you to believe and not what the actual facts are. I have been re-tensioning belts and re-useing barely worn belts for years and have NEVER had a vehicle that has had a belt failure due to this proceedure. The newer HTD-HSN belts are all 100,000 mile belts and I usually re-tension my customers cars belts at 50 to 60,000 miles and replace them at the manufactures recommended mileage or at the customers request. | ||
| '75 308 GT4 (Peter)
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So Herbert, if the popular belief is not to re-tension F belts, why do they put the access hole? | ||
| Sam NYCFERRARIS (Sam)
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Hey guys, What a spectacular engine Herb's got there, it is a shame to put it back inthe car it is a beauty..love those Krinkle black valve covers and has anyone noticed that cute CORVAIR nose (beautiful color) in the background. I bet when Herb tells 'em " Yeah I have a Ferrari and a rear engine sports car" everyone thinks Porsche...guess again! Very interesting | ||
| Herbert Edward Gault (Irfgt)
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You can re-tension most all modern cars timing belts that have some wear slack. Contrary to most beliefs, the belts do not stretch but wear, which causes some looseness after some use. Honda even has an external nut that you can periodically adjust the belt. Even Ferrari has a hole in the timing cover so you can reach the tensioner without disassembly. | ||
| Michael Fennell (Mfennell70)
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"if it loosens up, you need to replace the belt." That was always my impression but my mechanic knows as much as there is to know about the Esprit (he was the Field Engineer for Lotus Cars USA for years) and he knows how I drive the car so I trust his judgement. I am guessing this was a pretty minor adjustment. | ||
| '75 308 GT4 (Peter)
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You hit it right on the nose Timothy. Leave'em slighly lose, turn engine over by hand two revs, check cam-mark alignment and if on, lock'em down. | ||
| Timothy J. Dressel (Tjd)
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Michael and Greg, This may be obvious to you, but I wanted to comment that the spring loading is only for the setting of the belt tension. Once you bolt it in place, the spring tension is no longer being applied. Also, it's my understanding that once the tension is set and the engine run, it shouldn't be reset and shouldn't need to be; if it loosens up, you need to replace the belt. Corrections and comments invited. --tim d | ||
| Timothy J. Dressel (Tjd)
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Herbert, Nice pictures. And I've been meaning to say thanks for sharing you engineering with us. --tim d | ||
| Greg Rodgers (Joechristmas)
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Mike, I am not sure on all Ferrari V8 Engines but on the 308 it is spring loaded. It is not like on the Esprit where the nut is loosened and the tensioner bearing/eccentric is turned until the belt tension is 95lbs. The 308 will pull tension on the belt through a spring loaded mechanism and applies the correct pressure on the belt automatically. I hope that this helps. | ||
| Michael Fennell (Mfennell70)
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Belts have a number of advantages from an automakers perspective. They're cheap and quiet and (to be a little cynical) provide a nice service revenue stream. I have read that 'quiet' is actually the driving factor. Is the adjustment on Ferrari V8 belts manual? My mechanic just tightened the belt on my Esprit (I actually check it by hand and thought it was OK. Oops). Unpleasant things can happen at 7000rpm with a loose timing belt. | ||
| '75 308 GT4 (Peter)
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Patrick, I think (and obviously they did at the time) the use of bevel gears and shafts to drive the cams is a very good way to go. Bugatti did this back in the twenties, they had incredibly close tolerances on their parts (to 0.0001" and less! So close in fact, that the engines don't use gaskets). Ducati's Desmodronic system is similar, I don't think revs are a problem, as you may know how fast those engines spin! Back-lash on the gears, costs of engineering and weight are main reasons you don't see them on every engine. | ||
| Herbert Edward Gault (Irfgt)
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The pulleys are the same width as stock as is the belt. The addition of the guides to both sides gives an illusion of being wider. The tensioner pulley is larger to compensate for the two additional teeth that the belt has. There is a slight clearance problem on the rear bank cover with the idler pulley on sone applications that is corrected in 60 seconds with a grinder or file. These systems are available for order. The 4 valve system is in the works and a different company that is less busy is working with me on the project. This company makes a lot of the machine parts for some of the most prominent Nascar teams. | ||
| Bill Sebestyen (Bill308)
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Herbert, Your system looks great. Nice job. Very clean and robust in appearance. The belt/pulley system appears a little wider than the stock system. Is this the correct? Are there any timing case clearance issues? Bill | ||
| Herbert Edward Gault (Irfgt)
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Here are some installed pictures of my updated belt system using Gates HSN Belts       | ||
| BretM (Bretm)
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Most engines when they overrev (or at least my experience with American high performance engines) is that the lifters start to float (although the Ferrari has solid ones I think) or that above a certain rpm the engine just doesn't produce anymore hp and starts to go down. I never met a case where it overreved and destroyed an engine, it's not really good for it though. Yeah I often wonder about the whole belt thing too, older Ferraris were driven by chains because they old engineers didn't trust belts at all back in in the day in Italy...trust them now? For the most part I think they are really reliable, but still there is always something about a piece of rubber spinning at ridiculous speeds in a really hot engine compartment that makes me raise an eyebrow. I would think a chain would add significant power loss in friction and in weight, and something about a piece of metal spinning at 10000rpms isn't all that kosher either. Looks like we can't win. | ||
| Patrick S. Perry (Psp1)
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My overrev question was more related to valve or camshaft damage which in turn might stop the camshaft from turning, thereby having the belt break, not due to wear or overrev directly, but by having something else impede it's normal movement. I don't have first-hand knowledge, I'm merely speculating. Please excuse my ignorance here (this board is one of the best learning tools around) but if the timing belts are so critical, why are the cams not direct driven off of the crankshaft with a series of gears? Is it a question of power loss? If that is the case, how much power are we talking about vs. a tradeoff in reliability? It seems for most of us, the timely replacement of timing belts is the most expensive concern - the reliability of the rest of the engine seems quite good. Are we sacrificing dramatically better reliability and less maintenance for minimal power losses? Thanks in advance for the education! | ||
| BretM (Bretm)
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Good point Patrick about the rev limiter, you most certainly can overrev that way. I would think that Gates would make a belt for Ferraris. I'm pretty sure they make older Ferrari belts so I would think new ones would also be around. | ||
| Frank Parker (Parkerfe)
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I have no idea why the cam belt broke. I just saw the car at FOA and talked to a friend of mine who works there about it. The car was scheduled to come in for a 30,000 mile service in five days when the cam belt broke . The cam belts in most Ferraris are made by Pirelli where most other cars use Gates belts. I suspect Gates is a higher quality belt than Pirelli. I wonder if you can cross-reference and use a Gates belt instead of a Pirelli one in a Ferrari ? | ||
| Herbert Edward Gault (Irfgt)
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If this story is true then I would suspect some part failure or a factory defect in the assembly. I do not believe a timing belt will fail due to high rpms. The A/C belt that drives the compressor turns approximately the same speed as the timing belt and the load is greater on the a/c than the cam belt. He could have over revved the engine and broke a valve and in turn broke the belt. There are a lot of possibilities and I would not let it scare everyone into running out to get new belts unless it is time by your owners manual. I have never seen a belt failure that could be attributed to high RPMs. I also am replacing belts on Hondas that have been on since the factory installation in 1990 with no signs of age deteriation. These are 12 year old belts with 100,000 miles and still look like new. By the way I have sent out the first orders of the 2 valve timing gear and belt systems and am working on the 4 valve system. Anyone that wants a 2 valve system can let me know. | ||
| Patrick S. Perry (Psp1)
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From what I understand, a rev limiter will save you from overrevving as you accelerate, but if you downshift into an innappropriate gear (see Britany Spears), you can overrev and do damage. | ||
| BretM (Bretm)
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I'm sure it has a rev limiter. | ||
| Patrick S. Perry (Psp1)
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I know you said that the engine was damaged by a broken cam belt, but if the engine was overrevved, could that damage the valves which in turn would cause the cam belt to break? | ||
| BretM (Bretm)
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I think this is an isolated case and that it's total BS that something like this happens to such a new car with hardly any miles on it. Ferrari should repair something like this on their own and stand behind their product. | ||
| magoo (Magoo)
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Where's Herb? | ||
| Frank Parker (Parkerfe)
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I spoke with a friend today from Ferrari of Atlanta. There is a 1996 355 Spider there with 25,000 miles with a damaged engine caused by a broken cam belt. It will cost $20,000.00 to repair the damaged valves and pistons. It seems 5 tears and/or 25,000 miles is too long to wait for a cam belt change. Makes me think about the 18 months and 10,000 miles since the one in my 348 was changed. |