Snapped a timing belt!!

[willy86]

hey there did not have a good day yesterday, snapped a timing belt and the fucking thing is only like 15000kms old http://www.ae86drivingclub.com.au/forums/emoticons/tdn.gif anyway just a quick question about clearences on bigport valves, ie am i likely to have bent valves and shit or can u get away with snapping a timing belt on a 4age and not do any damage to the motor?

[Jason]

its a non interferance, your fine

[willy86]

thank fuck for that.... now for the other question, y did i snap a brand new timing belt, they should be good for 100000kms???

[AE71GZE]

i think to tight is the main reason ..I snapped a timing belt in a cb80 engine with similar k's after rebuild ..with no clearence and put a piston up through the valves ..not cool on a rare engine haha !

[mattysshop]

did you use a new tensioner also? i'd be inclinded to say it was to tight also http://www.ae86drivingclub.com.au/forums/emoticons/smile.gif

[willy86]

as long as i havnt poped valves and shit timing belts are cheap. if the motor has had work done can it become interferance? or am i good?

[biggo]

depends how far you decked the head/ how small the head gasket is.

[willy86]

all good now boys, doesnt appear to have done any damage to the motor but apparently the crank gear was a bit 'how u going' and insted of getting another one my mechanic just said he cleaned it up and put it back on http://www.ae86drivingclub.com.au/forums/emoticons/rolleyes.gif other thing was he reckons too much advanced timing will put extra load on the timing belt causing it to snap whereas everything i have read about 4age's is as long as it doesnt ping crank as much advance in as u can???

[terryo]

the lower pulley is usually damaged by ham-fisted people trying to lever it off. The belt will never damage it. The problem with advanced timing is that the motor is hard to start and can even try to run-backwards on starting. if you have a loose belt, it can jump a tooth at this time. it really is not a clever thing to do. the timing value selected is optimised for the stock engine.
I have never seen a belt break just from over-tightening so quickly. usually, the noises from the idler bearing are horredous before this happens. I'd be looking very carefully at all the pulleys for nicks or damage that will damage the belt.. when fitting a new belt, we carefully examine every pulley and sand/file/polish them as required.
I agree that while 4AG's are non-interference from new, that is not the case once rebuilt and if cams are changed.
Sounds like you have it in hand