Help with snapped belt

[5imon]

Hey chaps,

just changed all my rockers and the crankshaft won’t do a full rotation now. Any ideas?

[plasma]

Timing is out? Did you line it up using the Mark's on the belt

[5imon]

Yeah set the timing up perfectly. I have just taken the belt off and spun the crank on its own. It jammed even without the cam belt on. I then turned the camshaft about 3hours and it freed the crankshaft up again. Only for 3/4 of a rotation though.
What I did notice was that when I spun the crankshaft without a belt on when it jammed it would turn the camshaft slightly. Surely that’s a bent valve???

[troutybrown]

If you turn crank without belt on then pistons will hit valves

[5imon]

Cool, I will attempt to correct the timing when I get the belt back on

[MrF]

Crankshaft timing belt pulley might have broken loose of its keyway and spun out of alignment
If you get a new pulley you'll most likely find that the old pulley wasn't aligned with the crankshaft

[5imon]

hmmm things have gotten really confusing. The engine seems impossible to time now. when I place both the crankshaft and camshaft on their set timing points (put belt back on) the engine will not turn over (Piston hitting values). I kept messing about with all different variations of the set points, meaning the camshaft @ 4oclock and the crank at 2oclock. I kept changing things to see if I could get one smooth rotation of the engine. I managed it but the timing points were wayyyyyyyyyyyy off. it turned over by hand smoothly enough but would not start with the key (it made an awful noise as well)
I think it might be time to put it up for scrap :-(

[MrF]

hmmm things have gotten really confusing. The engine seems impossible to time now. when I place both the crankshaft and camshaft on their set timing points (put belt back on) the engine will not turn over (Piston hitting values). I kept messing about with all different variations of the set points, meaning the camshaft @ 4oclock and the crank at 2oclock. I kept changing things to see if I could get one smooth rotation of the engine. I managed it but the timing points were wayyyyyyyyyyyy off. it turned over by hand smoothly enough but would not start with the key (it made an awful noise as well)
I think it might be time to put it up for scrap :-(

Timing belt Crankshaft pulley - left handed thread so right loose left tight, stick it in gear and use a breaker bar to undo it or use an impact wrench as its FT

I will bet money that crankshaft pulley has broken loose of its keyway and spun, buy another (they are seriously cheap <£20) and replace it, you'll most likely find the new pulley is in a completely different position when installed than the old one ended up - mine was after a 60mph timing belt snap

Also you probably have several snapped rockers - I had 8, thought I'd gotten away with 4 till I looked closer and saw another 4 had hairline cracks

[5imon]

Ok I will try and get the crankshaft pulley off, I suppose I will know straight away if its chewed its teeth up?
I have replaced the full set of rockers already, I hope more havent snapped when I tried to turn it over :-(
Are you sure its right loose left tight, I am turning the pulley bolt in opposite direction to a normal bolt thread???

[MrF]

Yep its left hand thread so reverse to "normal" bolts.

Its the key inside that rounds off its corners (basically a bump on the inside thats meant to lock into a slot on the crankshaft but its not that big so a timing belt snap at speed can round over the corners and allow the pulley to rotate around instead of being locked into one place)