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Thread: Mazda 929 Engine rattles... chain loose?

  1. #1
    Junior Member
    Join Date
    Apr 2010
    Brisbane, Australia

    Mazda 929 Engine rattles... chain loose?

    i've been messing around with the timing on my 1978 mazda 929, 1.8ltr.

    It only has 94,000 kms on it, or so the logbook says from the old people I got it from. I'm not 100% sure tho. the rocker gear looked really shiny and clean when i replaced the rocker cover gasket (compared to my ol' 75 crown at least, which was brown and yucky) at least.

    "Why the hell would you mess with your timing, you'll run it too hot and blow up your engine!" :evil: was what one of the guys at work said.
    too late, the deed was already done. playing with it, not blowing it up.

    actually my reason for this was pretty legitimate, I had just replaced the distributor cap, rotor, points and condenser doobly-doo. They were way past their due!

    Anyway, I thought I heard knocking/pinging in the engine when I first got the car (which, by the way was not long ago at all) and I assumed once i fixed up the timing it would would go away. But it didn't seem like it did.

    no matter how I turned the distributor, the little rattle didn't go away. it was like a shhh tshhh tshhh when i tugged on the accelerator, at probably only audible when speeding up the engine on the 2000-3000 rpm? but then I'd let it rev down and the rattle would come back for that certain rpm range.

    I talked to another mate and he mentioned that he thought the timing chain was due around 100,000 ks. I don't see any record of it being done. Could it be what is rattling around, rather than it being pinging? And is there a way of tightening this up a little, without removing the engine? (which is what all the guides I have tell me to do... maybe there's a reason for that.)

    Because all considered, I'm not 100 percent sure what pinging sounds like. I thought it was a dull rocky-kinda rattle. one of The Lifters are ticking a bit, should I adjust them to spec, to cut out some of the engine noise first?

    And tell me someone what if i'm doing anything wrong with the timing:

    Step one: rotate cylinder 1 (indicated by dizzy) ignition at 8BTDC (the third little white mark. whats the second one just after TDC for, anyone?)
    Step two: Rotate distributor, so points are just starting to open. I left the keys on "on" to get a current, and used a circuit tester light between the two point. I set it so the light was *just* coming on. Is this correct for static timing? What else can I do without a dwell meter/vacum guage?
    step three: Tighten everything up and drive, if it makes un-natural noises pop the hood and retard it a little more...

    Any comments, suggestions or critical advice will be very very appreciated. I hope to take some pictures of my old-school cruiser-wagon soon!

    Sorry about the MASSIVE post-essay without any pictures

  2. #2
    Join Date
    Feb 2010
    start with the basics and check your oil.
    then set your valve clearance HOT.
    then in all liklihood you are dealing with a carbon choked piston - you need to give it an italian tune up - alternatively run some sort of fuel additive to clear her out. A sympton of a carbon choked engine is occasional run-on after shut down and pinging under load.

    Timing chain is a possibility.
    But so is a gudgeon pin.
    And so is a lean tune/partially blocked carby.

    Without hearing the engine noise i can't determine it.

    Sounds like you are capable of doing the job. The internets won't do it for you. You need to get dirty and get on with it.

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