Questions on timing chains vs. timing belts, TIA.

If it moves, anything is mileage dependent.

But you have a couple things round the wrong way, sorta. Taken in order:

1.) Belts are mileage dependent too. They just wont run forever. Seeing many MB cars have gone past 300K miles on original chain's, I would guess the chains win. However, not all chains are created equal. Notice many Ferrari have three row chains. Very robust.

2.) I believe the failure rate on belts far exceeds any chain driven cars, on cars that exceed thier mileage limits, old American V8 technology notwithstanding.

3.) On cars that sit a lot, it seems the belts take a set and accelerates the deterioration of the belt. Cars that sit dont instantly start rusting, so again, the chain will win.

4.) Chain driven engines may be a tad bit shorter, but except for the actual links and pins that make up the chain itself, I dont think there are really any more parts per se.

So why a belt? Its my belief and understanding, that it was first used in racing. Ferrai jumped onto it, as well as a lot of racing engine designs, purely for a performance reason, not a durability reason. The belt is way lighter compared to a chain. For the same reason you would get a lighter flywheel, or lighter rods, pistons, or valves, the belt carries and requires less inertia.

Think of trying to accelerate the timing system from idle. Every gram of weight extra is weight the engine has to move to accelerate. This is why we had plastic timing cogs with small diameters, and belts. It will not make more HP, but it will accelerate faster.

 

1 Yes
1a No
2 Maybe
2a No. Where did that come from?
3 Yes but close to a draw
4 Length dependant on design. Yes

Answers predicated on subject being modern motors, a comparison of new belt drive and new chain drive, not the chain drive that dates back to the 30's as installed on the 166, 275,365 etc.

 

I suppose as an intellectual exercise, yes.

I have seen motors started that had been sitting for decades, poss 20 years and the chain did not break. In other words it is a complete non issue.

Every thing else in the motor will be junk before the chain is a problem.

 

My 1972 Lotus has a timing chain. It's the original one and will last the life of the car. It is never considered a normal service item. The only thing we DO service is the chain tensioner. It does reach the end of its travel eventually and is replaced/repaired. This too may never happen in one's lifetime however.

The key is on an engine rebuild to have the tension correct to begin with. My chain is lubricated with engine oil so once set, not a lot can go wrong. In all the years of Europa ownership and being in a Europa group, I have never heard of a chain breaking either first, second or third hand. I hope I'm not jinxing myself!

Ken

 

All things being equal, chain (and gear) driven engines are also infinitely less prone to oil leakage. A chain driven DOHC has 1/4 the seals of a belt driven one. In addition, the gaskets in general are a lot less complicated on a sealed drive system. There are just less places to leak, plain and simple.

A blanket statement, but chains deal with lack of tension a lot better than belts as well. The teeth are significantly taller (as a ratio of chain width) than in a belt, which generally uses short, wide teeth.

 

They are also quieter and allow for a simpler (and less expensive) casting of the block.

 

I don't know how massive of a chain Lotus uses, but chains do wear, and stretch. Usually, the stretch is taken car of through the tensioner, and generally, when the tensioner has reached its limit, the chain should be replaced. If a chain breaks, it can as much or far more damage than a belt would ever do, because it can wind up on the lower sprocket and break the block.

 

My car is only a 1.6L engine that's really detuned from its top potential as a race engine, so it's not stressed very much at all in street configuration. You are correct that when the tensioner is at the end of the travel the chain is replaced; I'm not aware of anyone ever having done this (from wear as opposed to rust or deterioration) on a Lotus Twin Cam engine. Even the assembly manual says this is unlikely to ever happen.

Ken

 

Well all I have to say is that my truck has over 184,000 miles on it and the chain is still running strong. Yet I had to put a new timing belt in my 348 at 56k miles. I doubt you will ever see a timing belt that can go 200,000 miles, or more, before it needs to get changed.

Chains win.

 

belts are cheaper to manufacture than chain.
This is the reason there are so many Toyotas and other econoboxes that run belts.

Erich

 

Excluding Ferrari's which we all know leak - I have never had an engine out service because of leaky seals - what would you drive that would make you think 100,000 miles is time to pull the engine? My hauler Pathfinder has 130,000 miles, I have owned two z cars with 100,000+ miles an Infiniti with 85,000 miles (I know it's not 100,00 but close enough) and NEVER pulled an engine to replace seals.

 

Now hold on here guys. Yes, belts are cheaper, but that is NOT why Ferrari used them. They used them for a performance reason, everyone else used them because it was cheaper engineering and cheaper parts. Do you see small diameter belt sprockets on Jap cars, or any other car made in the world? No.

Regarding engine out service. If you owned a Lola, or a Can Am car, or perhaps a Ford GT-40, one that had a race motor, or perhaps a 288 GTO, or a F-40, you would be pulling that motor out after every weekend and freshening it up. I don't know about today, but not many years back, track driven hotted up street motors were generally torn down after 20 hours, or after any long endurance race. Why? to protect your investment. You dont want to wait till it blows apart, you want to salvage all the internals and the block. Racing engines many times do not operate at the speeds your Ferrari does in every day use! Take your Honda out and crank it to 8K rpm all day, week after week and see how long it stays together. These Ferrari are not Hondas, and were never meant to be. They are race cars that are "detuned" to be street driven, PERIOD. Our belt change requirements are in keeping with a hard driven track car. I guess if some of you dont like maintaining a race car, you should maybe buy something else.

 

Krowbar, I like your passion for all things Ferrari but….
The Honda S2000 does wind to 8k and beyond all day.
Please pardon my somewhat skeptical attitude toward Ferrari but look at the situation from a pure business perspective.
1. Belts are cheaper to produce. Reduce production cost/ increase profit on the front end.
2. Belts in Ferraris require unusually high maintenance costs. Increase profit on the back end. An evergreen revenue stream!
Not a bad business model!

 

As I understand it belts are more efficient than chains, but chains are more reliable.

Interestingly the new motor in the F430 has reverted to chains.

 

All new motor designs since F50 are chain drive.

 

Japanese motorcycles use chain drive, and rev to where no street based car can even think of going to.
The chains last as long as the motor does.

 

Would it be right to say that a tensioner problem is more likely to cause a toothed belt to jump than a chain & sprocket setup?

 

Oh boy!
Another timing belt thread!


My thoughts.....

Well, my Ferrari has timing belts.
It was time to change them, so I did.

What's the big stink?
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No. Ford twin cam and Dino V6's just to name 2 were famous for tensioner slippage that caused blowups. Also Maserati/Citroen V6's

 

Seriously, lets not compare apples to watermelons here. You ever seen the cam drive chain in a motorcyle engine? Most are smaller links, shorter in length, than on a bicycle. I doubt that tiny little chain weighs anymore than a belt for a 308. And further, motorcyle engines, because they are designed for high rpm torque, have very light crankshafts that would never hold up to pushing a car around, as well as thier light weight cams. Oh, and those little chains inside motorcycles break too.

I would assume, that with all the yelling Ferrari owners are doing over belt replacement and maintainance, and seeing as Ferrari is working harder to satisfy customers, everyone probably got what they asked for, a glorified Honda, instead of something more cutting edge. Because in the giant scheme of things, when Ferrari was one of the first F1 teams to go to belts on a F1 car, I doubt it was to save money. I also doubt they were trying to save money on 308's, 348's, 288's, F-40's, or 355's, by using a belt, they used belts because it made better power. I would also make the assumption, that Ferrari went with chains on the F-50 because it was worth the power loss compared to damaging 5 valve per cylinder V-12 heads in the event a belt broke. Everything in life is a compromise somewhere, no matter if its boats, cars or airplanes. Would the belt on a Ferrari last 100K? Maybe. Is it worth it? I guess that depends on what its worth to own a Ferrari

 

I WISH my car ran on a chain. My fear of the catastrophic event would be reduced by 50%.

And my enjoyment would go up 200%.

I would trade 20 HP for a chain. THAT is how much the belts on these cars scare me.