“odds are more of the belt driven ones would surrender first.”
quite likely due to the fact that many owners don’t replace the belt at the correct mileage/age, or don’t replace it at all, for that matter
One of my former service advisors saw me changing the timing belt on my own car. He thought I was crazy. He said “A timing belt is something you change when it breaks, not as preventive maintenance.”
Naturally, that philosophy will only work with freewheeling engines, and only if you don’t get mind getting stranded
it won’t work so well with an interference engine, or if you’re driving through a rough part of town
I agree that a broken belt is likely one that has been forgotten or ignored. My point was that if it’s a matter of running a car until the cam drive mechanism breaks then belts will give up before chains more often than not.
The service advisor’s comment shows exactly why most of them don’t need to be within 20 country miles of any car.
Why did manufacturers gravitate away from timing gears, and instead rely on timing belts and timing chains?
Gear drive? Impossible. Well probably not impossible but crazy. How are you going to get gears to drive the camshafts on a V style OHC engine. Or even on a 4cyl OHC? I would think the system would be horribly complex and expensive.
Yeah, Mrs JT just won’t part with her Silhouette. It’s 12 years old, the fuel gauge stopped working, it has a little engine oil leak, a few other problems, but she won’t let me sell it or donate it and buy a replacement.
Using metal timing gears requires expensive machining of the components and adds considerable time in assembly. Gear drives for overhead cams would be particularly time consuming. Some motorcycles have opted to use a shaft driven bevelled gear for OHC drives.
And when assembling there would be several sizes of each gear to choose from and select fitting them to achieve the proper mesh is required. Most gasoline engines with timing gears use a plastic cam gear. The GM 2.5L 4 cylinder was famous for stripping the gear and the engine needed removal to replace the pressed on gear.
The GM 2.5L 4 cylinder was famous for stripping the gear and the engine needed removal to replace the pressed on gear.
And back to my oil question…if the quality of motor oil and metal manufacturing was as good when that engine was designed as it is today, would those gears still have failed in such numbers?
Poor lubrication didn’t seem to be the cause of failure @asemaster. I often suspected that for some reason, likely detonation from carbon buildup, the crank would reverse for a second. The plastic gears always failed with a section stripped out by the crank gear. Ford I-6 cam gears failed similarly.
Of course Everything wears out eventually. Automakers aren’t in the biz to make engines for us that last forever…wouldn’t be good business you see.
Now lets say tomorrow an automaker declared that they just spent the last few years developing their Piece de resistance Longevity engine…this engines philosophy was that it would be removed from the vehicle when the rest of the car died and transplanted into a new vehicle frame without much refreshing… What do you think that engine would look like? Would it have plastic valve covers? Would it have a Timing Belt? Would it have a cast crank and rods? You bet your sweet ass it wouldn’t.
Think Diesel engines in Locomotives. Ever see their Cam Gears? They’re works of Art actually… Bad cylinder? Replace just that One cylinder…not the whole blocks worth… Those loco engines were designed to outlast the humans who built them…and they DO…and Often. Oh and they cost an absolute Fortune too…hahaha
We don’t see silly systems in automotive engines because we couldn’t come up with anything better, or didn’t have the metal knowledge Hells no. We had it since before WW2 actually.
What we get in cars today is basically pretty damn good…especially from some countries other than the USA…although we are getting “better” in engine designs (read making Less money on old designs because we had to invest more in engines and systems because we needed to stay competitive and stop milking designs from the early 50’s)
Engines today are pretty nice we all have to admit. There are weaknesses in all designs but i would venture those weaknesses NEVER stem from our knowledge of metal nor design abilities…They stem from The Bean Counters desks…mark my words. That is what I believe to be true…and I’m pretty sure I’m correct.
Now if people would enrich their brains with just even the basics of what is under their hoods today…we wouldn’t see such failures in engines that were starved for oil…or never had the oil changed! GASP!!! and this shit happens all the time… cars are just appliances to people…they barely care or want to know how they work…let alone want to know what kind of crankshaft was used in their Straight 6 Twin Turbo BMW.
We have had the tech, the metal, the know how for longer than Ive been alive…I assure you. We are getting the best the mfg’s will give us per profit margin…
Forty years ago I spoke to an engineer with considerable experience in farm machinery and trucks regarding a patent and it was his opinion that the combination of bean counters and computers (remeber, 40 years ago) had resulted in the ability to design in acceptable failure. He mused that Henry Ford walked onto a steel component yard and picked up several beams and considered the weight of his Model T. When he found one he felt certain would never fail on his car he picked it up and had his front axle made to that specification. Today engineers can consider the normal demands of a piece of equipment and calculate that a 2% failure during the warranty period is acceptable and shave down the dimensions while reducing the stencil and shear strength of the alloys to strike that “perfect” failure rate. And just think how much better computers are today compared to 1975.
CHEAP is the very last word that would have come to mind while viewing this work of art. Funny you showed this… This is exactly what the Huge Locomotive Diesels cam drives look like…albeit a little larger…but the same principle. Can anyone say…“Longevity is Oil Dependent?” for this setup?
