| Author | Message | ||
| Jon Honeyball (Jhoneyball)
New member Username: Jhoneyball Post Number: 2 Registered: 4-2003 |
Chains seem to be much longer lasting, but might well be noisy. Certainly in my baby (89 Aston Martin V8 Vantage) chain breakage is unheard of, and lasts a 6 figure mileage. There is one obvious reason for Ferrari using belts. It is a huge tax on the owners. Every three years you have to go back and have those belts replaced, which is often an engine-out job. The cost per mile driven can be $3/mile or more for a typical low-mileage low-usage car. Is this a good or a bad thing? Well, having a vibrant dealership network is definitely a good thing. And extracting $3k per car every 3 years is a good way of doing that. Personally, I think it is bad engineering that requires you to have to drop the engine out every 6k miles (2k/year for 3 years) to change a belt. This cannot be good engineering by any proper definition of the term. | ||
| rich (Dino2400)
Junior Member Username: Dino2400 Post Number: 192 Registered: 10-2001 |
a ha! that makes perfect sense PSk! I guess we hope people are only going to need to change chains as often as they rebuild the engine so people will probably have it out of the car and all apart. I've changed a couple of belts in my day and some are easy and some require stupid stuff like draining all coolant and removing crank pulley and so on. Just part of the fun I guess! | ||
| PSk (Psk)
Member Username: Psk Post Number: 390 Registered: 11-2002 |
Rich, Yes can see your point regarding the Dino engine. What I was refering to is say Alfa Romeo 4 cylinders engines that have a lower and upper chain. Obviously you can change the upper chain by connecting the new to the old once the cam cover is removed ... but the lower one can only be 'got at' by removing covers ... I should try and explain myself a little clearer. Thus if you can get at all the chains with little difficulty then this is a good idea ... if you can't then off the covers have to come and much more time required. Pete | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1719 Registered: 1-2001 |
Sure -- but only if convenient for you JRV. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1359 Registered: 11-2002 |
>>any photos of the gear trains handy? Is there only 1 intermediate gear?<< Steve, I might have photos in storage somewhere of the Pegaso gear arrangement( I'll try & find some, the owner of 0937 that I restored also had a Pegaso I worked on for him))...most of these exotic type engines used multiples of gears to drive the neccesary components . [I know I have some pics of a 4 Cam Carrera I did a few years back. if you'd like to see those?] | ||
| rich (Dino2400)
Junior Member Username: Dino2400 Post Number: 183 Registered: 10-2001 |
PSK: "Naturally the replacement idea (ie. connecting the new chain to the old chain) will only work on engines where there is a single timing chain, such as many modern Japanese engines ... like Ford Lazers, etc. " I'm not following your thinking here. The dino v6s have chains for each bank and it would be as easy to replace both as it would do to just one. Here's a diagram of how the chains and gears look: http://www.3jar.com/fiat/dino/images/motor2.jpg | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1717 Registered: 1-2001 |
JRV/Bryan/Psk -- thanks for the examples -- any photos of the gear trains handy? Is there only 1 intermediate gear? | ||
| PSk (Psk)
Member Username: Psk Post Number: 389 Registered: 11-2002 |
P.Thomas,
Good point, but gears usually take a lot longer to wear that bad and thus usually are okay. I am talking here of normal road cars not high class engines like Alfas and Ferraris, etc. But saying that I have never seen a gear so badly worn that it has needed replacement. Naturally the replacement idea (ie. connecting the new chain to the old chain) will only work on engines where there is a single timing chain, such as many modern Japanese engines ... like Ford Lazers, etc. BTW: Regarding gear driven camshafts. The most famous and winning F1 engine ever, the Ford Cosworth DFV has gear driven camshafts ... but the 4 cylinder version used in Formula Alantics has belt driven camshafts ... BTW 2: The Porsche Carrera 4 cam engine for the 356 model used shafts and spur gears to drive the camshafts and was a nightmere for mechanics to setup ... definitely not the way to go. Pete | ||
| Peter Sedlak (Peters)
Junior Member Username: Peters Post Number: 233 Registered: 1-2003 |
In place of a chain or a belt, how about a single gear? It seems that there is room in or outside of the block for this. Am I 'out to lunch' with this idea? | ||
| 89TCab (Jmg)
Member Username: Jmg Post Number: 439 Registered: 9-2001 |
I was talking to a few folks at our local dealer about the Ferr-whoops-Maserati engine, they figured it would be turning around 470-480 hp and a couple of inches shorter if it were belt instead of chain driven. I got the impression that this was the target that I should expect for the 360 replacement. - JMG | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 550 Registered: 11-2002 |
IME it comes down to cost and design/packaging considerations. Indy cars and the like run chains for the past decade give or take mainly (but not exlusively) for packaging issues. Even Ferrari must take cost into consideration for design/manufacture. For a while belts sufficed, now looks like chains. | ||
| Bryan Phillips (Bryanp)
Junior Member Username: Bryanp Post Number: 82 Registered: 8-2002 |
The overhead cams on the 4 cylinder Ferraris of the 1950s were gear driven - 500 Mondial, 750 Monza, 860 Monza - all the Lampredi-designed 4s. | ||
| Russ Turner (Snj5)
Junior Member Username: Snj5 Post Number: 110 Registered: 2-2003 |
4 cylinder Carrera 4 cams (mechanically the most complex VW ever made)have a gear driven shaft drive. Twin distributors driven off the cams Bugattis have a set of watchlike appearing gears to drive overhead camshafts. What a whine! There was a great thread once about different kinds of belt drives (square tooth v. round tooth?), and one lister offered a conversion to a newer more durable belt/tooth type for 2v 308s - any comments from folks with this? | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1356 Registered: 11-2002 |
>>I've never heard of an overhead-cam, overhead-valve engine with a cam gear-drive arrangement -- has anyone?<< Pegaso's & Porsche Carrera 4 Cam engines come to mind..also Buggati I believe, the first two for certian. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 575 Registered: 4-2002 |
As to gears: the VFR motorcycle (revs to 12,000 RPMs) uses gear drive to 4 overhead cams (V4 engine architecture). about 6-8 years ago it changed from chains to gears. There was some mention of better control of cam timing. However, the 15,000 PRM motorcycle engines all seem to be I4 and chain driven. | ||
| Tony Fuisz (Fuiszt)
Junior Member Username: Fuiszt Post Number: 52 Registered: 10-2002 |
How about going to a non-interference piston/valve design then? Then belt failure would just mean it won't run, not catastrophic engine problems. I think the belt design is to allow the engineers to adjust the reciprocating mass via the flywheel, instead of having all sorts of heavy metal turning in different parts of the engine. | ||
| Martin - Cavallino Motors (Miami348ts)
Advanced Member Username: Miami348ts Post Number: 4437 Registered: 5-2001 |
I think this age old question gets always out of context. It is rarely the belt that needs changing. The tensioner/pully bearings go bad. With those you loose strength and have a possible tooth jump. Since a Ferrari engine is not a Corvette engine (I can hear Arlie already...)you prevent certain possible "problems" from happening by routinely changing parts like the tensioner bearings. While you are at it you also change the $60 beltm, because it just makes sense. As for the belts. The only premature failor they have is due to the constant heat/cold cycles they have to go through. It is after all a rubber/plastic mix and you heat that up to 350F and back down to 70F a day later back up to 350F and down to 70F. this is what will cause chemical reactions in the compound and "age" the material. The only person I know that had a belt failor is Chris Parr. We talk about the failor a lot but actually know only one case. The question is: It it worth taking the risk? | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 102 Registered: 4-2003 |
Rich cool pics! You guys gotta check that out. that puppy is torn all the way down. | ||
| rich (Dino2400)
Junior Member Username: Dino2400 Post Number: 179 Registered: 10-2001 |
Yes, some cam chains have master links. The chains on my dino engine when I got it had them. The new replacement chains did not, which required removing the gears from the cams to install the chains. Not a huge deal (assuming the engine is on a stand), but adds an hour or two of time since there are four cams to do and get them all lined up properly and such. My home rebuild photos are here and show the chain fitting (don't be too horrified by the vice grips - i'm sure there is a factory tool for that but every mechanic we called said just use the grips and forget about it...): http://www.3jar.com/fiat/fiats.php?p=rebuild | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 101 Registered: 4-2003 |
Gear drives were most commonly used in the old days on small block Chevys. Sounded kind of cool, like you had a blower.....Or horrific starter/flywheel grind where you forgot to release the key in the ignition. Ha ha. I think even helical cut gears would sound horrible in an F-Car (if it could even be done). The ONLY plus to gears is that you have a zero veariance in crankshat/cam timing. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1712 Registered: 1-2001 |
Gears are really only practical for a pushrod (or flathead) engine where the distance from the crank to camshaft is not too large (and even then the noise and inertia issues aren't pluses) . I've never heard of an overhead-cam, overhead-valve engine with a cam gear-drive arrangement -- has anyone? | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 568 Registered: 4-2002 |
I find it interesting that the only two options on this table are chains versus belts. Why are gear drive not even in consideration? | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 100 Registered: 4-2003 |
JRV, I really never thought of the timimg chain as a fix all/cure all. I was really thinking outloud about PSK's blurb on the R&R of a timimg chain without removing the cover or changing the gears (nylon or metal teeth). That would be self-defeating right, like pissing in the wind. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1353 Registered: 11-2002 |
P.T., Chains can have their fair share of problems. They are not the free & easy solutin to driving cams most try to make them out to be when trying to compare chains to belts. Yes they are very reliable and durable in some instances, they are not without their share of issues. Like PSK alludes too, someday maybe a plainly better way of getting the jobs done may come along...but for now, it's 6 of one and a 1/2 dozen of the other when comparing chains & belts. Each design has it's issues, just different issues. I think people lean towards chains because you can ignore a loose noisy chain (for awhile) but you can't ignore a big cam seal oil leak. | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 99 Registered: 4-2003 |
Had a thought: If a chain is stretched over time, then the spacing on the teeth of the gears will be out of tolerance. I think that if you just replaced the chain and not the gears , you would end up quickly stretching the new chain. | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 97 Registered: 4-2003 |
PSK, "you can link the old chain to the new chain". Are you suggesting that there is a master link, like on a bike chain? I have never looked at a chain that closely. | ||
| PSk (Psk)
Member Username: Psk Post Number: 388 Registered: 11-2002 |
Chains can be implemented badly too, refer Jaguar XJ12 v12 engine with (I think) a simplex chain or a single duplex chain doing the whole thing. Compare that to the early v12 Ferrari engines with triplex chains and separate upper and lower chains. Also Triumph Stag engines ... same thing, and Morris Minis which always rattle away with stretched chains. In the end if you want performance and quiet operation you go for belts. If you want an engine that is more fault tolerant you go for chains (find me a quiet German engine and I'll ... Mercedes engines are amazingly noisy but they are very, very reliable and a Porsche engine is not exactly a mechanically quiet thing. Guess BMWs are reasonably quiet). Note: my father was service manager for a company that also sold a Japanese brand (name withheld so they do not sue  ) and one year their new model came out with belts and the mechanics had to listen to the big sales pitch on why they had gone to belts, etc. The next year (or when the next model came out) they went to chains and they had to listen to another sales pitch and close to the reverse of the last one was stated by the same company Some race engines even use gears, but I would think that belts would be superior to gears due to the low mass to accelerate, etc. Some really old engines used shafts with spur gears on each end ... Best solution is to remove the need to drive camshafts, and find a better method of activating the valves ... BTW: Most chains can be replaced by connecting the new chain to the old chain and turning the engine (keeping tension on the chain as it comes out and the new is fed in), thus all you have to remove is a cam cover, or equivalent ... piece of cake. But lets face it cam belts are not exactly hard to replace either ... it just takes time to remove all the crap in the way and the covers. A definite do yourself job if you know which end of a spanner to use ... I do not think you can sh!t on either design ... failures are usually caused by lack of maintenance. Pete ps: There are many Japanese cars and vans that have gone past 300,000 kms and they run belts ... but I guess they have been replaced as designed. | ||
| stephen r chong (Ethans_dad)
Junior Member Username: Ethans_dad Post Number: 227 Registered: 3-2002 |
Yup...hee hee The type 930 motor really is a lovely design after all these years though. | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 96 Registered: 4-2003 |
That makes a little more sense. I thought to myself, pre-Carrera no tensioners at all? = engineer flaw=kaboom. | ||
| stephen r chong (Ethans_dad)
Junior Member Username: Ethans_dad Post Number: 226 Registered: 3-2002 |
Oops. Forgot. The 3.0L SC's had either sealed or open reservoir chain tensioners. These were less reliable than the later pressure fed Carrera tensioner. | ||
| stephen r chong (Ethans_dad)
Junior Member Username: Ethans_dad Post Number: 225 Registered: 3-2002 |
P. Just the opposite; the3.2 Carrera introduced spring loaded, hydraulically dampened tensioners. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1351 Registered: 11-2002 |
<<I'd trade that for the lower weight of a belt in a street car any day.<< Well, many manufacturers don't agree with that, Porsche and Ferrari among them. | ||
| Ken (Allyn)
Member Username: Allyn Post Number: 843 Registered: 10-2001 |
Chains remove a major headache from the equation. No one in the Europa group has ever mentioned a broken chain; it's just unheard of. It's the most bullet proof part of the Twin Cam engine. Other cars may be different. I'd trade that for the lower weight of a belt in a street car any day. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1350 Registered: 11-2002 |
>>OK, I'll admit it was nearly time to have them done anyway.<< Tom, Chains stretch and have to be serviced and/or replaced periodicaly or if they have automatic tensioning the tensioners have to be replaced periodicaly. So far no one has come up with a design that isn't a series of compromises of one sort or another or that won't break. | ||
| rich (Dino2400)
Junior Member Username: Dino2400 Post Number: 178 Registered: 10-2001 |
Isn't Ferrari going back to chains? I think the current Maseratis have chains, right? I hope they expect them to last "forever" because on modern engines with all the junk around the engine, changing them would be horribly difficult (though doing the belts on Ferraris isn't all that quick either, huh?). On the old cars with more room and/or less stuff to disconnect before pulling the engine out to work on it, it wasn't such a big deal. I will say that the dino has chains and it's part of the sound! | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 95 Registered: 4-2003 |
Hum, I thought that pre-1984 (pre-Carera) had hydraulic tensionser (similar to what Toyota used on their 20r, 22RE, etc. The pre-Carrera "upgrade was to go to mechanical tensioners? No tensioners at all sounds really dangerous, like a granade with the pin pulled. | ||
| stephen r chong (Ethans_dad)
Junior Member Username: Ethans_dad Post Number: 223 Registered: 3-2002 |
P. Actually the tensioners became a factory standard on the 1984 3.2 Carrera. All 3.0 SC's had no chain tensioners from the factory, and were more subject to chain failures. Either motors are pretty solid though. 3.2's were the first factory 911's to enjoy the benefits of motronic engine management systems. | ||
| P. Thomas (Ferrari_fanatic)
Junior Member Username: Ferrari_fanatic Post Number: 94 Registered: 4-2003 |
JRV, good point. On P-cars up to 1983 (SC models) the tensioners were upgraded to Carrera or mechanical units. Then you would literally have a 200K longevity motor. I guess with F-Cars then other parts would have a shorter longevity then a chain correct? ie the chain would outlast the valve seats or valve guides?? | ||
| Hans E. Hansen (4re_gt4)
Intermediate Member Username: 4re_gt4 Post Number: 1157 Registered: 4-2002 |
What's annoying, however, is that typical belt drives give more opportunities for oil leaks. I'm having belts done right now because of a drive sprocket seal problem. OK, I'll admit it was nearly time to have them done anyway. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1346 Registered: 11-2002 |
>>Any help JRV?<< The others explained chains vs belts beautifully. Now chains with hydraulic tensioners (P-cars up to 83 for example, early diablos, Mercedes, etc ) suffer about the same failure interval (of the tensioner) as belts...approx. 40K-50K mi. and have the minor? drawback of depositing metal fileings directly into the engine as the gear teeth wear. However, historically chains & belts still seem to be running neck & neck as favorite choice of Super Car Builders . | ||
| Jack (Gilles27)
Member Username: Gilles27 Post Number: 723 Registered: 3-2002 |
I have read that, with chains, your risk of a breakage shifts from the belts to the teeth. | ||
| Chris F. (Chrisfromri)
New member Username: Chrisfromri Post Number: 37 Registered: 1-2003 |
It's all about engine responsiveness. Belts have less much mass and are therefore much more responsive. Ferrari placed a priority on responsive performance rather than the more rugged but sluggish performance from a chain. Both can clearly be engineered for any engine -- it's just a matter of priorities during the engineering process... Kind Regards, Chris | ||
| Henry D. Chin (Hanknum)
Junior Member Username: Hanknum Post Number: 99 Registered: 2-2002 |
Timing chains are obviously heavier and thus take more energy to spin (rotating mass even worse) and are noiseier, but do last longer than a belt. T-belts have all the opposite attributes to the above but require routine replacement, though the intervals seem to be increasing over the years. My $.02 Henry | ||
| Martin - Cavallino Motors (Miami348ts)
Advanced Member Username: Miami348ts Post Number: 4426 Registered: 5-2001 |
I had asked that question an expert in racing and his reply was this: The timing chains carry a much higher weight and therefore the forces are higher the higher the chain revs. Okay so he explained that much better than I can. Its about the forces that the weight of the chain creates flying around at high RPM. | ||
| stephen r chong (Ethans_dad)
Junior Member Username: Ethans_dad Post Number: 219 Registered: 3-2002 |
Chains require lubrication, which in hand leads to internal placement in the engine design. Pcars (911) have internal chains and seem to experience fewer failures than the dreaded 308 TBelt horrors. Belts I suspect permit them to be external, and could be easier to access for service/replacement. Just a guess. Any help JRV? | ||
| Lawrence Yee (Ferrariguy)
Junior Member Username: Ferrariguy Post Number: 117 Registered: 8-2002 |
Good question. I think timing chains should last much longer but cost more. | ||
| Erik (Teenferrarifan)
New member Username: Teenferrarifan Post Number: 37 Registered: 2-2003 |
I know that the 400/412 had a timing chain, also a few other production cars have them such as the cadillac northstar engines and many more. What are the pros and cons of a timing chain over a belt? Why don't more F-cars use Timing chains? Is it a performance issue? This was just a question I was pondering. Erik |