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Thread: keyway failure on a 20v?

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    Moderator Sam-Q's Avatar
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    Default keyway failure on a 20v?


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    I have had my engine stuff up at max revs, and as it looks the front crank pulley is turning when I crank it and the cam belt doesnt turn. So from this I think I have somehow managed to break the key out of the keyway for the timing belt drive gear. I have heard of people wrecking the keyway for the main pulley but not this sucker.

    Has anyone ever heard of this?

    I am hoping my crank and some of my valves arnt damaged or else I will be pissed off.
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    Senior Member KE70's Avatar
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    Dammmm, that would have been scary.

    Are the keyways the same across all 4ages?

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    Senior Member Matt-AE86's Avatar
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    Sam, if you remember ages ago Josh/mr2drift killed the keyway on his 16v 4age when it was turbo. He thought it was due to milling off the front half of the crank pulley.

    I'm pretty sure he got a new one and replaced it.

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    Veteran slydar's Avatar
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    its a some what common problem. unless youve put cams in your engine or had machine work done your valves will be fine, no 4age is an interference engine standard.

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    Senior Member Hen may possibly be a nut's Avatar
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    As you probably know, the timing pullye and crank pulley run on the same key, so it seems a little strange that one would go and not the other.

    I once snapped a crank just behind the timing pulley. Apparently it's not an unknown problem, but then your crank pulley shouldn't be turning.

    Not hard to get the plastic covers off and see what's going on though.

    Hen

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    Veteran slydar's Avatar
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    yeah, the timing gear has the resistance of the valve train to fight. rest doesnt have much resistance at all.

    its a pretty common problem. the 2 gears on the one key way is the problem in theory. the 2 pulleys move/vibrate ever so slightly all the time, at different frequency's, due to their different loads. putting a lot of fatigue cycles on the key.

    Atlantic engine have 2 separate key ways, 1 for the timing gear, and another for the accessories.

    sheering the key way is kind of a mark of honor. you must rev your engine pretty hard sam fairly often.

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    Senior Member Vezza's Avatar
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    Quote Originally Posted by slydar View Post

    sheering the key way is kind of a mark of honor. you must rev your engine pretty hard sam fairly often.
    Haha, the new in thing... you ain't cool unless you've sheared a keyway. We can start a KS club, keyway shearers.

    Just wondering Sam, has the crank pulley ever been removed and reinstalled? Maybe if the bolt wasn't torqued on tight enough, it could've had a slight play, rocking back and forth until it sheared the keyway?

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    definately that?? it could be possible your tensioner has died and possibly sheared off teeth on the timing belt? I have seen it happen before, otherwise a seized cam and then snapped, odd if neither cam is moving... just soem food for thought

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    Moderator Sam-Q's Avatar
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    KE70: I can only assume so, unless thats what caused the problem as by memory I fitted a 16V keyway??

    Matt-AE86: I find it a bit odd that machining the front of the pulley off might of killed it?? I would of thought that it would of reduced the load because there would be less innertia on it?

    slydar: I thought it was only a common problem for the actual front pulley not the cam timing gear. As for the whole intereference thing I thought about it and I have two things that make it an unknown; I was doing more revs than what the engine is normally limited to and also I am running a 0.8mm trd head gasket. Just for the record I was doing 8500 RPM in third at the time.

    hen: the covers will come off soon, I just made this thread yesterday after being towed home. I just parked the car and left the damn thing for the day.

    Vezza: I did have it off and I will check for freeplay later, although I would of thought the main pulley would go first?? also this isnt the first time I have broken something in a new way. A while back I smashed the diff so good that one of the teeth broke in such a way that shot out through the rear of the diff housing, and that steel isnt thin...


    dustyae86: I tottaly didnt think of the fact that I am missing a few teeth off my timing belt. I will have a look thanks
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    Moderator Sam-Q's Avatar
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    well I have found the problem, it looks like I did use all the right parts however the pulley was missing the top part of the keyway that holds the semi-circle shaped key in place. So while it would of worked for a while the key eventually curled out for the lack of a better explination. Looking closely at it, it amazes me how little of the key is used to transmit the torque to the main pulley, no wonder they fail. I will fit another pulley tomorrow and find out if my valves are bent.
    My website: SQ Engineering - 4AGE and 3SGE upgrade/replacement parts

    - SQ Engineering on facebook -

    Please e-mail to contact me instead of sending a private message on here.

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