Belt or Chain (timing, that is)

I thought the other thread would be about this.

I've never owned a car with a timing belt. All of my previous cars and current cars have chains, which I prefer for the reliability factor.

Not too concerned about a bit more noise

Owned/own both.

If you change tbelts at the right interval, they are quite reliable, although I think I still prefer chains

On chains, you also have tensioners that fail, plastic rails that wear, chains that stretch ... and they are usually PITA to change.

spnx wrote: I thought the other thread would be about this. I've never owned a car with a timing belt. All of my previous cars and current cars have chains, which I prefer for the reliability factor. Not too concerned about a bit more noise

I way prefer belts. Chains and their guides are wear items, are expensive to replace, and are usually dependent on oil quality and pressure in order to work properly. Sucking the oil pan dry in a corner might kill the engine from timing chain failure before the bearings get hurt.

It doesn't hurt that the OHC engines I like to play with have belts that cost $10 tops and have simple methods of tensioning. Move a pulley or rotate the water pump, no hydraulic gimcrackery.

This reminds me, it's been 80,000 miles since I replaced the belt on my car. I HAVE a new belt but I'd prefer that it goes on the next engine.

Belts... easier/cheaper to maintain.

belted engines have twisted to over 14,000 rpm with rarely a problem

Also, seems that belts actually feature less parasitic power loss than chains.

I hoped this would create a discussion! I really don't mind working on an engine with a chain.

However, I must admit I've not only never owned a timing belt car, I've never worked on the guts of one either.

erohslc wrote: Also, seems that belts actually feature less parasitic power loss than chains.

Note that they're playing with internal belts now. Oil-friendly materials so it can live inside the engine.

Not sure if it's a good idea or bad (plus: theoretically fewer leak areas and simpler sealing surfaces. minus: THE BELT IS SOAKED IN OIL) but there you have it.

Also, three words: Jesel Belt Drive.

How much of a pain will it be to change an internal belt? What happens when it fails?

I much prefer a chain, but OHC anything is a royal PITA.

Pushrods are my friend!

Gearheadotaku wrote: How much of a pain will it be to change an internal belt? What happens when it fails?

Looks like we get to find out! The Ford 3-cylinder is apparently using one. My guess is that it's no "worse" than dealing with a chain, except with no guides.

I much prefer a chain, but OHC anything is a royal PITA. Pushrods are my friend!

A shaft drive might be neat if there were no harmonic issues. I know that's how it Used To Be Done when engine RPM was kept low. Ford's 1000ci DOHC all-aluminum V8 used shaft drive, for example. When they made a DOHC version of the 221/260 for Indy, they used a clockwork like maze of gears instead of running a shaft up.

I've worked on both, and don't understand the hesitation about belts as long as the service interval is reasonable. On the Toyota v8 the service interval is 90,000 - 100,000. For me that's a decade of driving and it takes about one day to do the belt. No big deal.

I've bought two with broken timing belts (one interference, one non) and both were due to extremely poor maintenance. The one had the original belt at 200k and the belt still didn't break - one of the 200k mile idlers seized and the heat melted the teeth off the belt! The other the water pump seized - this time after ~160k - and took out the belt.

I have yet to see or hear of a case where a properly maintained good quality belt failed. So doing a belt once every 100k miles - when you should do your water pump anyway - doesn't seem like a hardship.

Oh, I meant to add - Alfas have like 30k intervals and flakey tensioners so they're known to fail early sometimes. That would be a problem. But a well engineered timing belt with a reasonable service interval? No big deal at all.

seems that nissan timing chain guides last around 60k-ish. that's less than alot of belts.
They start wearing away and eventually the tensioner tries to make love to the chain, with no protection from the guide. that doesn't work out too well and they generally cause catastrophic failure=]

warning signs of this are an awesome whirring whining noise when revving at all times.
I've seen 150k cars with no problems, and I've seen 25k cars with timing chain guide whine.
I think it might be cheap oil.

I'll +1 the belt preference, with the caveat that I'd be worried to buy a used interference engine with a belt unless I was going to replace it immediately

I have owned way too many Fiat Twin Cams.. the belts on those are a serious wear issue at around 20,000 miles. That said, I can do one of those belts on a 1.8 in less than an hour. The 2.0, with it's splash guard around the lower pulley takes a little longer as you need to remove the crank pulley and splash guard

corytate wrote: seems that nissan timing chain guides last around 60k-ish. that's less than alot of belts. They start wearing away and eventually the tensioner tries to make love to the chain, with no protection from the guide. that doesn't work out too well and they generally cause catastrophic failure=] warning signs of this are an awesome whirring whining noise when revving at all times. I've seen 150k cars with no problems, and I've seen 25k cars with timing chain guide whine. I think it might be cheap oil. I'll +1 the belt preference, with the caveat that I'd be worried to buy a used interference engine with a belt unless I was going to replace it immediately

This: for all the timing belt hand-wringing I've seen a lot more chain-related issues on Nissans and Toyotas than belt-related issues on Hondas and Subarus.

Gearheadotaku wrote: How much of a pain will it be to change an internal belt? What happens when it fails? I much prefer a chain, but OHC anything is a royal PITA. Pushrods are my friend!

You really think so? I always found setting up all the rockers and their rod and pivots to be a bigger pain than OHC.

ShadowSix wrote: This: for all the timing belt hand-wringing I've seen a lot more chain-related issues on Nissans and Toyotas than belt-related issues on Hondas and Subarus.

I understand that the new Subaru engines have chains. (As do basically every Honda designed in the past 15 years or so)

I wonder how they're dealing with the boxer harmonics. On DOHC Subaru fours with manual transmissions, there are guides around some of the pulleys to keep the belt from bouncing off. I'm assuming that automatics don't need them because they have the mother of all Fluidamprs on the back of the crank to damp out any strange harmonics, and the SOHC don't need them because they have more even loadings on the cam pulley.

mad_machine wrote: You really think so? I always found setting up all the rockers and their rod and pivots to be a bigger pain than OHC.

STOCK pushrod engines are pretty okay.

Last week we were running the lash on a customer's car (BIG mechanical roller cam, Joe Sherman wouldn't call it "girlie", lash is checked every time we see the car, which is about 2000-3000mi) and the rockers were starting to eat away at the tops of the valves. Not signficant, mind you, just a little bit. So, on go a set of hardened lash caps, after I made a little fixture to grind them all to .100" deep so they'd clear the keepers.

Running the lash again. Feels... weird. I step back and look at what I'm doing. I have a .020 feeler under the rocker, the Poly-Lock is finger tight, I can barely move the feeler, and I can take the pushrod and wiggle it around. The super-awesome Crane rockers were bottoming out against the Poly-Locks thanks to the added valve height. So we need to go with longer pushrods.

But wait, there's more! With .100/.200" longer pushrods, the Poly-Locks would only grab the studs by four threads. So longer studs are required.

But wait, there's more! The longer studs also have longer threads on the end that go into the head. Fortunately (?) the holes are deep enough, but the intakes, which are not blind and extend into the intake ports, need to be de-gunked for the new studs to torque cleanly.

At least the valve covers still cleared the +.250 studs...

See, all this crap is why my personal toy-car is rotary. It has compression or it doesn't, and you make power by removing iron and aluminum, not by adding multiple quantities of expensive parts on a depressingly regular basis...

If those are the only two choices, I'll take a chain over a gear - one of the reasons I picked my Scion xB1 was many reports of 200k+ with no timing chain maintenance.

But if I get my real choice, I'll pick timing GEARS over the other tw0.

Belt, for the reasons already stated...

Where's that pic of the VAG 4.2L V8 Rube Goldberg timing chain setup...

My personal experience with chains is limited. We didn't have the S52 M3 long enough and the engine was never abused. MINI Tritec engines and current R56 engines both use chains. The Tritec seems pretty reliable, although I fear a tensioner or guide on the g/f's '03 MCS may be wearing. It might be serviceable with the engine in the car, but its not easy. A lot has to come apart... The R56 had some issues, but it seems to have been fixed after a couple of years. MINI did replace a few engines under warranty due to chain tensioner related failures.

On plenty of engines, the chain service interval is "never". I've had approx 15 timing chain engines and never needed to service a timing chain related component.

I can't comment on the enclosed belts they are working on.. but having worked on both chain drive and belt drive. I will take the belts. At least if you drop the belt, you do not need to fish it up out of the recesses of the chain's cover.

Belts are also a -much- lighter system and usually quieter. On a modern engine with an 80,000ish replacement interval, I also usually replace the waterpump as well. As they are usually located -behind- the timing belt, it's the perfect time to do it

ProDarwin wrote: On plenty of engines, the chain service interval is "never".

Right, it's like lifetime transmission fluid. When the transmission dies, you change the fluid.

I've only replaced one OHC timing chain. That was one where it was dealt with when it was just making noise from worn guides, instead of being let go until the chain whips around loose, breaks a guide, starts to jump teeth, binds in the process, breaks, and then gets wadded up and thrown through the side of the timing cover/engine block, leaving an unrepairable mess.

Timing belts. The fact that every 850+ hp engine in Nascar uses them says a lot. They're quieter and dampen engine harmonics. They are usually a bit easier to change/replace than most timing chains. If you have an engine that is not an interference fit, there really is no downside. The belt breaks, you replace it and keep driving. If it breaks with an interference engine, then things get messy and costly. Timing chains. Been around for a hundred years and are very reliable. Maybe too reliable. Nobody ever changes them until they are stretched too far or break, normally causing much bigger headaches when that happens. In my experience, with engines that have tensioners, that is usually what goes first. No tension, the timing chain slaps around, wearing a hole in something, or just making the engine run like crap.

If its a non interference engine... I run it till it breaks. The least I've gotten out of a factory belt thus far is 210k (it was an 80k interval belt) I've had issues with a chain stretching but again... Over 200k miles so I tend to trust both. If you run your car hard enough odds are you'll tear up something else and just replace the belt of chain while your in there.

NASCAR engines do not use timing belts, they still use the old fashioned gear drive for the cam. they do use belts for accessories. Most important is the oil pump.