Chain vs Belt

Is there a reason manufactures use timing belts rather than chains? I have had both and if I can help it I will not get another car with a belt (edit) as a DD.

Belts are cheaper. Fiat as far as I remember was the first to use a belt on the cams.

Belts are typically quieter. Belts run outside the oiling system (for better and worse). Belts have a shorter life but are easier to change. You do NOT want to change the chains on a quad-cam Vee engine!

That being said, my DD also has a chain ('05 Scion xB). When the chain fails, it will probably be used up in many ways.

Belts are far more accurate than chains. Belts do not stretch and wear the way chains do.

OK, so why not gears? If they can create a 7-speed paddle shift intelligent transmission, why not similar technology for timing?

I have seen timing gears for a lot domestics. Are there any reasons for to use timing gears?

anyone know what F1 and the like use?

pinchvalve wrote: OK, so why not gears? If they can create a 7-speed paddle shift intelligent transmission, why not similar technology for timing?

for one they are LOUD. fine if you have a blower or something making more noise nearby, but pretty anoyng on a DD. ask me how i know!

My 98 Explorer has the 4.0L SOHC engine.

The cams are driven off the timing chain for the OHV cam. One bank off the front and one of the back. Good thing they are chains, that back one might be a teeny bit difficult to change.

pinchvalve wrote: OK, so why not gears? If they can create a 7-speed paddle shift intelligent transmission, why not similar technology for timing?

Think about how much more weight is going to be needed to run a gear drive for a DOHC engine. How much more rotating mass, costly extra machining, etc.

It can be, and has been done for Cam-in-Block engines, sometimes as an aftermarket upgrade for domestic V8s.

itsarebuild wrote:

pinchvalve wrote: OK, so why not gears? If they can create a 7-speed paddle shift intelligent transmission, why not similar technology for timing?

for one they are LOUD. fine if you have a blower or something making more noise nearby, but pretty anoyng on a DD. ask me how i know!

Not if the gears are cut properly.

If you've got the Jesse Jackson gear drive in your Chevelle, sure it'll make noise.

My Iron Duke, Ford 300 and IHC 345 never made any extra noise because of the gear drive.

The reason for no gear drive is all the extra monkey motion and rotating mass involved in an OHC gear driven arrangement.

I once saw a cutaway drawing of an engine from the 40's or 50's that used bevel gears and shaft drive for the OHC setup.

Shawn

81gtv6 wrote: anyone know what F1 and the like use?

F1 uses computer-controlled pneumatically-actuated valvetrains. No belts or chains involved. Maybe an optical trigger wheel. EDIT: No wait they still use cams to open the valves, which are driven by gears.

On topic: Belts for performance and durability, chains for impressing hot rod lovers

Trans_Maro wrote:

itsarebuild wrote:

pinchvalve wrote: OK, so why not gears? If they can create a 7-speed paddle shift intelligent transmission, why not similar technology for timing?

for one they are LOUD. fine if you have a blower or something making more noise nearby, but pretty anoyng on a DD. ask me how i know!

Not if the gears are cut properly. If you've got the Jesse Jackson gear drive in your Chevelle, sure it'll make noise. My Iron Duke, Ford 300 and IHC 345 never made any extra noise because of the gear drive. The reason for no gear drive is all the extra monkey motion and rotating mass involved in an OHC gear driven arrangement. I once saw a cutaway drawing of an engine from the 40's or 50's that used bevel gears and shaft drive for the OHC setup. Shawn

hmmm. not sure i am familiar with the jesse jackson version as most of what i see and hear at the strips is milodon. does the jesse jackson yersion sound like grinderation or whoosheration?

you are all missing the drag part, too- chains have more drag than a timing belt.

Just wait for you scared of belts getting wet with oil- the next step is a wet belt. And I'm not kidding.

(Gears are >>>>>> louder than chains, even cut right, but gears are more precice (or at least can be) which is why they are in race engines (where cam torsionals can be a problem))

Belts are coming back.

Eric

NGTD wrote: My 98 Explorer has the 4.0L SOHC engine. The cams are driven off the timing chain for the OHV cam. One bank off the front and one of the back. Good thing they are chains, that back one might be a teeny bit difficult to change.

I'm not so sure I'd say it's a good thing. Those early SOHC 4.0L engines like lose chains and destroy all kinds of stuff in the process. If it makes a weird noise, it's probably too late.

Chains last about as long as a belt but there are more ancillaries that keep them alive (guides, tensioners) and they're more of a pain and expense to deal with.

I'll take belts, thanks.

Plus, you don't have to worry about wadding a belt through the side of an engine block if you uncover the oil pickup at 6000rpm in a corner...

Belts are definitely quieter and cheaper. As far as longevity: Isuzu's recommended interval for replacement on the V6 engines was 105k miles. I would see the first breakages at around 165-170k and more than one over 200k with the stock belt. The drawback to belts is the same as chains: if the engine is an interference unit it will bend fold spindle and mutilate parts if it breaks. The Ford Windsor engines were real bad about plastic timing gear failure at around 125k and when they did puke man did they ever bend valves. So did the 3.8 Buicks. Newer timing chains have much greater lifespans, as in no recommended replacement interval.

Suzuki's 2.5/2.7L V6's used 4 chains under the timing cover and ALWAYS need a main chain tensioner. 7 hour job. They lasted about 100-110k IF you changed your oil early. 50k if not. I change the t-belt on the hyundais at 60k just to be safe. The whole job costs as much as the 'zuk's tensioner alone and takes 3 hours.

As far as I know the chain on my RSX has no replacement interval

My Sephia went 100k when I changed the belt.

Fewer belts all the time on new cars. Chains don't seem to be the issue they once were, and they are tiny now, compared to, say, an L series Datsun. Maybe thats why they give less trouble- less mass to fling around.

And transmaro- if you never had any extra noises from your iron duke because of the gears, you either didn't own it very long, or the car had a very loud stereo.

Extreme example, but a double row Bristol Hercules radial used gears to operate sleeve valves. I don't envy the RAF.

(hotlinked for complexity)

That looks like Swiss watchmakers worst dream.

my 4.6 has one mile long chain with a tensioner on each side.

i had a 3.4 dohc gm that was cool. they used a chain to drive a dummy cam in the OHV cam location but deleted the lifter valley from the block. the dummy cam drove the oil pump at the back and the front had a sprocket for the belt that drove the 4 cams.

16vCorey wrote:

NGTD wrote: My 98 Explorer has the 4.0L SOHC engine. The cams are driven off the timing chain for the OHV cam. One bank off the front and one of the back. Good thing they are chains, that back one might be a teeny bit difficult to change.

I'm not so sure I'd say it's a good thing. Those early SOHC 4.0L engines like lose chains and destroy all kinds of stuff in the process. If it makes a weird noise, it's probably too late.

They were already replaced on a recall.