timing belt snapped..help

[spunky424]

well i was cruising about 15-20mph in my hatch wit jdm b16 sir2...not even on the accelerator, jus rolling to a stop....when the motor shut off..i thought nothing of it and tried to start it back up..but it wouldnt start...it turns over but wont start..i popped the hood and the timing belt was hanging all loose ...i have aem cam gears on the car....well needless to say the timing belt snapped and i had to tow my car home...my question is..going at that speeed...could i have messed up my valves or anything?

thanx

[vthokie]

How old is this engine? If your timing belt broke, it is highly likely that you bent some valves. And if you tried to start the car while the belt was broken you almost certainly bent your valves. Did you hear any noises when it happened? I don't think speed really matters, in anycase, if the belt broke, you probably had the valve hitting the piston. You can do a leak down test or put a new timing belt on and do a compression test. In anycase you should pull the head. If you suspect a belt valve, Tip the head on its side. Spray a little brake clean in the ports. If a good amount leaks out...there is your bent valve.

[spunky424]

wut would i need to repair this type of damage? thanx for the reply...

[soundcolor]

I am not saying that it is impossible for you to have bent valves, but the pure physics of the situation really leads me to believe that there is nothing at all wrong with your motor...

Here is the reason.
First, the timing belt controls when the cams push the valves open. By design, if the timing belt breaks, then the cam stops spinning immediatly. Which slams the valves shut in the head... trying to start the motot would again, not hurt the valves, becuase the starter works directly on the flywheel, which turns the crank... and while the crank may well be rotating the engine, if the valves are not open (which there would have been no way for them to, since the timing belt was broken) and since the valves are not open then no fuel, or air could be sent into the chamber for combustion.

Now, unless you were at wide open throttle, and unless your motor was spinning at a faster rate than the valves can free-close (free-close is described as having no pressure holding them open from the cams) there is no way you hurt your motor... the only thing you might need to do is to yank the plugs and replace them....

you will definatly need to obvioulsy replace the timing belt, and make sure you do it to factory spec.

[sonictronic]

Originally posted by soundcolor
I am not saying that it is impossible for you to have bent valves, but the pure physics of the situation really leads me to believe that there is nothing at all wrong with your motor...

Here is the reason.
First, the timing belt controls when the cams push the valves open. By design, if the timing belt breaks, then the cam stops spinning immediatly. Which slams the valves shut in the head... trying to start the motot would again, not hurt the valves, becuase the starter works directly on the flywheel, which turns the crank... and while the crank may well be rotating the engine, if the valves are not open (which there would have been no way for them to, since the timing belt was broken) and since the valves are not open then no fuel, or air could be sent into the chamber for combustion.

Now, unless you were at wide open throttle, and unless your motor was spinning at a faster rate than the valves can free-close (free-close is described as having no pressure holding them open from the cams) there is no way you hurt your motor... the only thing you might need to do is to yank the plugs and replace them....

you will definatly need to obvioulsy replace the timing belt, and make sure you do it to factory spec.

ahh yes my friend physics are our friend.....however almost all Honda engines are interference engines which means that the valves can open far enough to hit the piston even at idle (sometimes in some engines). And if the timing belt breaks then yes the cams stop spinning but the valves that were open when they stoped spinning stay open. To explain that better.....not all valves open at the same time....when the valves in #1 are closed the valves in #3 could be open and so on. Even everytime you shut your engine off there are valves left open. For them to close the cam would have to dissapear which would totally defy the laws of physics.

However there are instances when the valves are in just the right position to save their ass and not get bent, but that is very rare.

To fix this you will have to take your head to a shop and have them replace the bent valves, probably the guides and other stuff unless you feel pretty competent doing it yourself. Also dont try starting your motor anymore...everytime the piston gets in the vicinity of the valves that are open is a chance to hit em.

[soundcolor]

Negative Ghost Rider....

what are you talking about, the ALL honda cams have a no-open fully closed design built into them, for this specific reason... timing belts do snap, Honda knows this, and designs this feature into all their cams... see, the spring keeps the cams closed unless the crank turns the timing belt, and in turn it turns the cam-gears which in turn turn the cams, which in turn opens the valves...

if the timing belt is not keeping the cams from rolling to their all-closed positin (which the timing belt does) then the valve springs return the valves to the fully closed position instantaniouly...

we are not dealing with GM's here...

[vthokie]

Originally posted by soundcolor
Negative Ghost Rider....

what are you talking about, the ALL honda cams have a no-open fully closed design built into them, for this specific reason... timing belts do snap, Honda knows this, and designs this feature into all their cams... see, the spring keeps the cams closed unless the crank turns the timing belt, and in turn it turns the cam-gears which in turn turn the cams, which in turn opens the valves...

if the timing belt is not keeping the cams from rolling to their all-closed positin (which the timing belt does) then the valve springs return the valves to the fully closed position instantaniouly...

we are not dealing with GM's here...

I'm confused on what you are trying to say by the "no-open fully closed" There is no way that the engines can have all the valves closed at the same time, unless you remove the cams. Yes we have interference engines,the whole purpose of this is just in case your belt breaks, you don't mess up all your valves. Just the ones that are open at the time of the break. Whatever is open or closed when break occurs is going to stay that way. Remember 1,4 cylinders go together and 2,3 go together. So if 1,4 are on their power/intake stroke then 2,3 are on their exhaust/compression stroke, (not to mention valve overlap),there is no way all valves can be closed at the same time. The cams have the lobes positioned on it to match up with the cranks firing order. In addition, weight of the moving car is turning against the flywheel rotating the bottom part of the engine..ie the crank--rods--pistons. These will keep turning unless you depress the clutch lifting it from the flywheel allowing the engine to stop turning against the weight of the car. This is why I think he has a good chance of having bent valves. But I have heard of people getting lucky.

Oh and what you said here

see, the spring keeps the cams closed unless the crank turns the timing belt, and in turn it turns the cam-gears which in turn turn the cams, which in turn opens the valves...

Is not a honda thing, every 4 stroke engine does this. Except the spring closes the valve (i think that is what you meant to say)

[spunky424]

Originally posted by soundcolor
I am not saying that it is impossible for you to have bent valves, but the pure physics of the situation really leads me to believe that there is nothing at all wrong with your motor...

Here is the reason.
First, the timing belt controls when the cams push the valves open. By design, if the timing belt breaks, then the cam stops spinning immediatly. Which slams the valves shut in the head... trying to start the motot would again, not hurt the valves, becuase the starter works directly on the flywheel, which turns the crank... and while the crank may well be rotating the engine, if the valves are not open (which there would have been no way for them to, since the timing belt was broken) and since the valves are not open then no fuel, or air could be sent into the chamber for combustion.

Now, unless you were at wide open throttle, and unless your motor was spinning at a faster rate than the valves can free-close (free-close is described as having no pressure holding them open from the cams) there is no way you hurt your motor... the only thing you might need to do is to yank the plugs and replace them....

you will definatly need to obvioulsy replace the timing belt, and make sure you do it to factory spec.

then how come many cars have bent valves or even worse when they snap timing belts?

[RulerJDM]

because in most cases the belt snaps at higher rpm.a friend
of mine snapped one at 30km/h and he was slightly on the throttle.
his valves were just fine.
I would just try fitting a new timing belt and see what happends.

[Dang Civic]

No matter how slow or how fast ur motor was goin ur valves are bent. I had the same problem a while back in my gsr ..just got into first gear and snap..did the same thing u did and after i got the timing belt replace i had a compression check done at a shop and they found out the valves were bent. Its highly improbable that the valves arnt bent. I think its like 1 in a 1000 chance tat ur valves arnt bent but i dono the exact number..its just rare. As for as someone on the board saying that once the crank not turning wen your timing belt rips..as long as the car is rolling ur crank is turning. I mean u can bend ur valves wen ur rotating ur crank so its very possible that ur crank rotates wen ur car is rolling. Best bet to do is just have a compression test done after replacing the belt or just taking the head off and checking it before u even change the belt yet. I dono..its just my logic. But i did take engine class last semester and i dont want to break open the book. Ur valves are bent tho. good luck. Oh..someone do correct me on the crank thing tho..i think im wrong. But the VALVES are bent.

[SFF900]

blah blah no one on here can tell you whether or not your valves are bent there is a chance they are and there is a chance that they are just fine, I have had the head off my car and played with it while out, all the valves on the motor can be *almost* fully closed at the same time. You just gotta get in there and check it out. Good luck I hope everythings good, If not its a good excuse to go with better cams and a valvetrain

[4point3S10SS]

yikes... just curious how many miles on the engine? my brother just replaced the belt in his GSR at 70k, so I'm wondering how close to a problem he was getting.

[chunky]

Originally posted by soundcolor
Negative Ghost Rider....

what are you talking about, the ALL honda cams have a no-open fully closed design built into them, for this specific reason... timing belts do snap, Honda knows this, and designs this feature into all their cams... see, the spring keeps the cams closed unless the crank turns the timing belt, and in turn it turns the cam-gears which in turn turn the cams, which in turn opens the valves...

if the timing belt is not keeping the cams from rolling to their all-closed positin (which the timing belt does) then the valve springs return the valves to the fully closed position instantaniouly...

we are not dealing with GM's here...

It's impossible for all the valves to be 100% closed at any given point in time on any inline 4 motor.

When the timing belt breaks, the valves freeze - any valves that were open stay open until acted upon by the piston. Any valves that were closed, stay closed.

So what happens when a piston nails a valve? At low speed, the valve gets bent - at high engine RPM, the shit really hits the fan. However- at low engine speeds, SOMETIMES the piston will just push the open valve closed w/o bending it (the cam rotates freely w/o the timing belt - valve pushes on rocker arm, rocker arm pushes on cam lobe) but this is pretty rare (it's rare in general for a timing belt to snap at low engine speeds).

But there is a point where all the valves are clear of the pistons - this doesn't mean they're all closed, but it does mean that the piston won't make contact at this cam position.

Honda can't predict at what point the timing belt will snap - so there really wouldn't be any benefit to designing a no lift fully closed point into the cam - b/c the chances of the timing belt snapping exactly when there is zero lift across all valves is almost nil.

Having a timing belt snap is better than having a timing belt skip a tooth though. THAT will fuck shit up hardcore. Just snapping the belt results in bent valves, or no damage if you're really lucky.

[hc99si1]

ive heard survival stories though of peoples belts snapping when theyre doing about 50 and their car was fine.
One guy i know bought a new belt and the car runs just fine, its been 2 years now!

[00BLACKSI]

Curious, how much does this cost and is it under warranty!!!!


Peace