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Jumped timing....

Posted by PeasantDSM, Jun 2, 2020

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  1. PeasantDSM

    PeasantDSM Probationary Member

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    Joined Jan 27, 2020
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    So I've been told by one half of people that the 420a is interference and the other half say it isn't... So on that note 2 questions.

    1). Is it or is it not an interference engine.



    2). Assuming it has jumped one singular tooth but the t-belt is still intact will it have bent valves?

    TIA....

    -Peasand DSM
     

    Street Build 182  2

    1997 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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  2. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Street Build 4K  29

    1992 Eagle Talon TSi AWD
    14.74 @ 117.04 · 1G DSM

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    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    755  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 1K  7

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

    Street Build 6K  13  25

    1990 Eagle Talon TSi AWD
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  3. 1995TalonMT

    1995TalonMT Probationary Member

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    Joined May 20, 2020
    Walls, Mississippi
    The 420A is an interference engine. My 1995 Eagle Talon with the 420A engine was one tooth off and it ran poorly, but it did not bend the valves. After I replaced the timing belt and timed it correctly it ran much better. I also replaced the water pump, tensioner, idler pulleys at the same time. I am not sure how far off it has to be before it bends valves but I suspect not much. Better to set the timing correctly than to chance bent valves.
     

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    1995 Eagle Talon N/T
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  4. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    My 90 GSX was off 2 teeth on the exhaust cam when I got it. The tensioner had failed letting it jump. If I hadn't bought the car when I did, I suspect the owner would have tried to drive it more and it would have jumped more and I would have been doing a head job.
    My Red 90 Talon had its crank pulley work forward from a loose pulley bolt and it ate ALL 16 VALVES. That was late in 2017 and I STILL don't have her fixed yet.
    Have you done a compression check yet? I would get some numbers from each cylinder and then post the results.
     

    Street Build 4K  29

    1992 Eagle Talon TSi AWD
    14.74 @ 117.04 · 1G DSM

    1K  14

    1990 Mitsubishi Eclipse GSX
    awd · manual · 1G DSM

    755  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

    Street Build 1K  7

    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

    Street Build 6K  13  25

    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  5. 609DSM

    609DSM Proven Member

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    Joined Aug 13, 2019
    Langhorne, Pennsylvania
    The 420a is a LOT more forgiving than the 4g63 when it comes to timing. I cannot fully confirm that it is okay being off 1 tooth although I highly suspect it will only mess with operation with little to no damage to the valves.

    I have seen people post on here with varying issues at idle and their timing ended up being 1-2 teeth off. They did a timing job and it fixed their issue.

    That being said the only way to know if there is damage is to inspect the engine internally.

    EDIT: and yes it is an interference engine, if someone is saying that it isn't they are ignorant on the 420a
     

    Street Build 233  2

    1995 Eagle Talon TSi AWD
    awd · manual · 2G DSM

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    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM
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