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Difference Between Belts

Posted by goldensmom (My Page) on
Tue, Aug 9, 05 at 11:30

To all you guys out there ... I have a question. Is there a difference between a serpentine belt and a timing belt? My brother says serpentine and I say timing so are they the same thing?


Follow-Up Postings:

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RE: Difference Between Belts

Goldensmom:
Yes there is a Difference. The serpentine belt is what runs all the various components on the front of the Engine. Your A/C pump,Alternator,Power steering pump, Etc. The TIMING BELT is used to operate the Cam-shaft which in turn operates the vale train assy. Back before the Auto Manufacturers decided to pinch every Penny they could,cars had numerous belts that operated the Various components that are now run by a "Serpentine" belt. As far as the Timing belt goes, some Vehicles still use a Timing CHAIN instead of a belt. I personally prefer the Timing Chain, and instead of 1 Serpentine belt, individual belts to operate seperate accsesories. If you lost a belt on the car equipped with a serpentine you're stuck, if however your Car had the old style setup with individual belts you could probably continue on to a shop and have the one broken belt replaced. I will say that the Sepentine belts do seem to last for quite some time though. Hope this helped you out.


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RE: Difference Between Belts

As the G.M. guy says there is a H%@LL of a difference between the 2. The serpentine belt turned inside out looks
like a 1 inch strip of a pair of real ugly corduroy pants.
Usually 7 groves for the main stuff and 5 for the alt. in the old vehicles that had two belts. The timing belt is treated against oil, vapours, moisture, and streching more
than the other one. It has horz. " notches " in it like the
steps of a ladder. The old Ford serpentines had steel in them thinking they would last longer. As the rubber wore
away the steel would slip on the pulley like crazy. You were
supposed to reverse the direction of the belt every 10,000
miles. If you turn your belt over to the under side, yes you can, and see thousands of little cracks it's time to
change it. Almost all engines that have the timing belt are
non interferance engines. If the belt brakes the pistons
don't get smashed by hitting open valves. Is this post O.K.
G.M.C. man ? Did i forget something ? I do agree with you
100 % about the chain. The 3 and 3.8 LT. fords use a chain
with a spring tensioner. You never need to change that chain. The old 235 chevy 6 had gears. One was celeron and
one was iron. The only thing that screwed that up was a
piece of cork from the valve cover gasket getting into the oil pipe and stopped the oil and the gear went dry. It was just a 1/4 inch copper pipe with a hole drilled in it pointed at the gears. Bitter voice of experience talking.


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RE: Difference Between Belts

Thanks GMC & kalining. Now I'm sure I've got this straight...when I open my hood and see that belt on the passenger side (92 camry) that's the serpentine versus the timing which I can't see so I will know when the serpentine belt needs replaced by looking at it. Just had my timing belt changed at 70,000 (maintenance) and that thing looked brand new when I asked to look at it. Didn't have a crack and sure didn't look like it stretched any. So if I'm looking at the right belt now (serpentine)it looks brand new also so at least I can keep an eye on that one for deterioration.


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RE: Difference Between Belts

"If you lost a belt on the car equipped with a serpentine you're stuck, if however your Car had the old style setup with individual belts you could probably continue on to a shop and have the one broken belt replaced."

Not necessarily--if the car has a timing-belt driven waterpump and it loses the serpentine belt, you can continue driving until the battery goes dead. (I also know of at least one engine with a timing chain that drives the waterpump on a separate belt from a pulley on the camshaft).

If there's a not-very-attentive driver behind the wheel, and the waterpump is driven by the serpentine belt, it might be better that way because the alternator warning light will come on if it loses the serpentine belt, hopefully alerting them to a problem..before the engine overheats and is damaged.


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RE: Difference Between Belts

Whenever I replace my serpentine belt, I keep the old one and throw it under the seat so I'll have a spare in case the serpentine belt ever breaks. This might be a good idea even if you don't carry any tools, because even if you had your car towed to a shop, there's a chance they wouldn't have the right serpentine belt available. If you had the old one they could put that one on and you could get home.


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RE: Difference Between Belts

Many mechanics I've spoken to say that even if a serp has cracks in it, they rarely "go". This is a gravy job, meaning easy to make money. Many times they'll show you the old serp and the cracks on the ribbed side. These belts can crack on the ribbed side only months after replacing it. If the ribbed side is cracked it'll still go for a long time. If the smooth side is cracked, then it's time to change.


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RE: Difference Between Belts

Almost all engines that have the timing belt are
non interference engines.

This statement is not true , Kalining
I guess there is some performance gain in having an Interference engine design..but what price for this efficiency ??

Better a man be prepared and do the preventative maintenance(necessary on the body and home as well)..

Trouble is , many dealers(Saab, for one) take advantage of this and the owners..and overcharge..
Then many owners never crack open their manuals and booklets and never participate in these forums..


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RE: Difference Between Belts

Earthworm. Sorry big guy. Never seen an engine with smashed pistons when a timing " BELT " breaks. That is a
non interference engine. Seen lots of busted pistons and
bent valves with timing chain jumps. If you have an interference engine, and they do have them, you will have
serious damage when the belt breaks. Show me an
interference motor with a belt. There is no performance
difference between the two engines. Performance has nothing
to do with anything. Most, if not all of the big three's
belt engines are non interference. A lot of the foreign crap doesn't have this option. You are supposed to change the belt before it breaks in all engines. Normal maintanence. Been in the business long enough that i remember putting a blob of braze on the end the fuel pump
push rod on a flat head to get the fuel pump to work again.
Remember that John G. ? Common problem with that engine.


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RE: Difference Between Belts

No, that is not true.

Most engines are "interference" engines, they need to specifically designed to be otherwise.

The old GM engines from the 70s didn't have a belt or a chain - the camshaft ran off a spur gear. When that disintegrated, the pistons would push the valves up against little resistance. They were interference engines.

If you break a timing belt there is no connection between the camshaft and the crankshaft, so the pistons just push the valves back up against no pressure and nothing gets broken.

On a timing chain engine, the chain usually breaks on one side only, so it is still connected to the camshaft.


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RE: Difference Between Belts

Big three ??, Kalining, you must be as old as I am ... lol
Now the "big three" are the Japanese, the Koreans and the Chinese !!!
Seems as if most engines are interference, but I know, from what I have heard, that some are not.. I find this a bit hard to believe now that I think of it...

The VW belt broke, for the last owner, cost $700 to R & R the head and replace valves, the pistons were OK...

Now ,yes, I remember that one with the fuel pump push-rod wearing down and being too short...Better to renew the rod($1.85), the braze, being soft, would not last that long...And $0.70 for a Chevrolet shift fork, or making new con-rod bearings from stock, or repairing a starter motor using masking tape and hammered bearings ..or running the VW 113 for less than a penny per mile!


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RE: Difference Between Belts

John999. " the old GM engines from the 70's didn't have a
belt or chain " ? What dream world are you from ? When that
chain jumped, (They don't and never break ). The cam stops
and will not move under the spring pressure. The piston will come up and smash the valves. No offence but you might want to open an engine and see how it works. You are
describing a double roller chain. They are used on 1000 H.P. motors and never break. The plastic cam gear is what
strips out. The cam off the " spur gear " is not a big 3
engine. 283,302,307,318,326,327,350,400,454,455, and so on
all have chains. Yes, Earthworm i think the big 3 is now
the Japanese,Koreans,and the Chinese. All chain engines are interferance. The chain isn't supposed to brake, they
don't but they jump. Hay,Earthworm remember pulling the flat head out of a truck and putting it into your car ? The truck engine had 110 H.P. the car motor had 90 H.P. Good god. I didn't think i was that old until i re read my post. All the best to everyone. That includes you John999. Hope you have a good week. Again john, no offence. Just don't know where you get your info.


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RE: Difference Between Belts

The Chevy pushrod six (similar to the Holden engine in Australia) that was replaced by the Buick V6 as the main GM 'six' in the 1970s (I think other GM divisions used different engines before 1976) had the camshaft driven off a spur gear - there was no chain. This was a pre-war design, although completely re-engineered in the 60s.

Double roller chains were commonly used on Japanese engines at least.

But I think what usually happens is that the plastic tensioner wears out or breaks off, so that the chain is flapping about and manages to skip teeth, or break a few, so then that valves get smashed as the chain is still connected. I know of a Mitsubishi engine that this happened to.


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RE: Difference Between Belts

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Posted by: john999 (My Page) on Mon, Aug 15, 05 at 5:42

No, that is not true.
Most engines are "interference" engines, they need to specifically designed to be otherwise.

The old GM engines from the 70s didn't have a belt or a chain - the camshaft ran off a spur gear. When that disintegrated, the pistons would push the valves up against little resistance. They were interference engines.

If you break a timing belt there is no connection between the camshaft and the crankshaft, so the pistons just push the valves back up against no pressure and nothing gets broken.

On a timing chain engine, the chain usually breaks on one side only, so it is still connected to the camshaft.
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John999:
No offense intended but your statement regarding Chvy engines from the 70s' in not at all correct. Almost ALL of those were run by a timing CHAIN . Cars and even some of the pick-ups used a CAM gear that had nylon teeth. When the teeth wore down enough, the Chain would jump a tooth and you'd have to go in and replace it. I personally hate nylon faced gears, opting instead for a good ole fasioned Cloyes Double roller set-up. In thier aim to quiet things down, the manufacturer made one more thing to wear out long before it should,based on it's original design. Now if you want to really get serious, go with a gear drive setup...AHHHH Love the sound of those.


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RE: Difference Between Belts

Here's a list of modern engines where valve interference is a possablitly. The list would be a lot longer if they went back to the high compression engine days of the 60's.

Here is a link that might be useful: Interference Engines


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