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Thread: xflow knocking/rattling noise

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    Bodger

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    xflow knocking/rattling noise

    Hi. Have a 1700 xflow which was rebuilt and put into my car last year. Has a bcf3 cam with +90 1300 pistons. I had my twin 40's setup on a rolling road and have been running the engine in, varying speeds etc but not going silly and all seemed ok. Last week i reversed car out of garage and warmed her up, revved it abit and suddenly i got this horrible knocking/rattling noise coming from the engine. I've just taken head off and found what looks like marks where valves are hitting the pistons possibly. Could this be the cause and why would it just suddenly happen and not previously when ive been running the car for several miles now. If its not that what else could it be? I'll put some photos below. Any help/guidance appreciated. Thanks.
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    Re: xflow knocking/rattling noise

    Normally its bearings in the bottom end...but could be flywheel come loose...cant see much wrong with the top end from the pics...cheers mark

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    Re: xflow knocking/rattling noise

    doesnt look like the valves have touched the pistons to me, but on a bcf3 they usually do at high revs if the pistons havnt been modified, so although they might if you were to rev it hard, i dont think that is your noise because although you can hear piston valve contact it usually sounds tappety, not knocky. knocking noise is nearly always a big end.

    im also slightly confused, you have had your carbs set up on a rolling road, but your now running it in? if it was set it up for full power/load then its already had max load on it and running in afterwards is pointless

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    Re: xflow knocking/rattling noise

    I agree with the other two posts, nothing wrong regarding valve to piston contact.

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    Re: xflow knocking/rattling noise

    i had valve contact on supposed BFC2 regrind. I never knew until ring lands broke with the shock of sending the valves back up into the head. The pics don't seem to show any contact. Although i always thought BFC2 was the max without valve pockets.

    when i rebuilt the engine i kept the cam and pocketed the pistons. It was an absolute flyer for a 1300. never knew what cam they had ground me
    Last edited by wildo105e; 25-01-2018 at 19:26.

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    xflow knocking/rattling noise

    Quote Originally Posted by wildo105e View Post
    i had valve contact on supposed BFC2 regrind. I never knew until ring lands broke with the shock of sending the valves back up into the head. The pics don't seem to show any contact. Although i always thought BFC2 was the max without valve pockets.

    when i rebuilt the engine i kept the cam and pocketed the pistons. It was an absolute flyer for a 1300. never knew what cam they had ground me
    Get a socket and bar on the front pulley and rock it to check for noise and play in one off the pistons ie they don't move when you move crank or listen for the flywheel loose or get a dti and check all your pistons

    Sent from my SM-G900F using Tapatalk

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    Re: xflow knocking/rattling noise

    check the "mission control valve" aint rattling if fitted then check that sump hasn't been dented then check big ends then check for woodpecker

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by fatboy slim View Post
    check the "mission control valve" aint rattling if fitted then check that sump hasn't been dented then check big ends then check for woodpecker
    good point, if the pcv valve is connected to the inlet manifold on 40's it makes a clacking noise

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    Re: xflow knocking/rattling noise

    Second piston picture looks seriously oiled up compared to the others, worrying.

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by mtt mark View Post
    Second piston picture looks seriously oiled up compared to the others, worrying.
    I think that's more water than oil via the head removal. Looks to be running comfortably rich so I guess the dyno was more just 'baseline' jetting FOR running in rather than FINAL jetting. If its a sudden knock then bearings are a good place to start looking unfortunately - they'll put up with a drop in oil pressure for a while then clack, clack, clack!

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    Re: xflow knocking/rattling noise

    Thanks for all the speedy replies. You're right, they just did a semi tune up to get the carbs set up right, suggested I ran it in for couple hundred miles or so then go back for full tune up. I shall get underneath and remove the sump see what I can see. Hopefully it is a bust bearing and hopefully it's not done any damage, I did turn engine off straight away. Will let you know what I find. Thanks again for your help.

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    Re: xflow knocking/rattling noise

    Hopefully it is a bust bearing and hopefully it's not done any damage
    99.9% of the time a "bust " bearing means crank damage

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by Graham View Post
    99.9% of the time a "bust " bearing means crank damage
    I'll second that, the theory is by the time you hear the noise the damage has already been done to the crank.

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    Re: xflow knocking/rattling noise

    It sounds like it could be timing chain rattle, possibly down to a non-genuine timing chain tensioner and/or pad not doing its job properly. On-and-off throttle or idling could cause cam to valve "clack".

    Just a thought. There's no substitute for an autopsy though!
    Last edited by HonkyWhiteTrash; 28-01-2018 at 14:22.

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    Re: xflow knocking/rattling noise

    Have we seen an answer to this rattle yet ?

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    Re: xflow knocking/rattling noise

    Got engine all stripped ready to come out, just waiting for a mate and his hoist to come round in next day or two and I'll let you know what I find.

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    Re: xflow knocking/rattling noise

    Engine finally out. Sump off, all looked OK. No metal flakes, no play in rods, everything looked nice and clean. Removed clutch and there was play in the flywheel, bolts were loose! I'm presuming this is the cause of the knocking. Will get them all torqued up and engine back in. Fingers crossed this hasn't turned out too expensive, just cost of a few gaskets. Thanks again for all the suggestions and feedback.

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    Re: xflow knocking/rattling noise

    Ha Ha Ha - notice how we all thought the worst and discounted the improbable LOL!

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by katana View Post
    Ha Ha Ha - notice how we all thought the worst and discounted the improbable LOL!
    It was suggested in first reply, but must admit you always envisage the worst !

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by upthevilla View Post
    Engine finally out. Sump off, all looked OK. No metal flakes, no play in rods, everything looked nice and clean. Removed clutch and there was play in the flywheel, bolts were loose! I'm presuming this is the cause of the knocking. Will get them all torqued up and engine back in. Fingers crossed this hasn't turned out too expensive, just cost of a few gaskets. Thanks again for all the suggestions and feedback.
    Hold on a minute don't be in such a big rush to get it back together. You need to investigate why the bolts came loose in the first place and what damage if any has occurred. The bolts will certainly need replacing with some decent quality ones like ARP. You also need to check for damage to the flywheel and crank mounting faces and to see if the bolt holes are elongated.

    The bolts came loose for a reason, either they have fatigue, weren't torqued up correctly or there was some previous damage that was n't noticed when it was built.
    Last edited by Forest_rallying; 01-02-2018 at 17:11.

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    Re: xflow knocking/rattling noise

    You're right of course. I shall check out everything you've suggested. Was probably just me not torquing them up fully in the first place.

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    Re: xflow knocking/rattling noise

    They need quite some torque, think at least 80 Nm ... and use new ones off course !

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    Re: xflow knocking/rattling noise

    Been bit ill lately so only just got round to finishing putting every back last weekend. At first engine wouldn't start, just popping n banging. Took plugs out and found 3 had their gaps closed up so opened up all gaps to the same and engine fired up....but sounds rough and cuts out. Sounds like a diesel! It's not the same knocking as before though, that's gone. When I removed engine I left the dizzy in the block, just removed cap n leads and I've put them back on in right order. Is there something I've missed? Anything that could have set the timing out as that what it seems like? Cheers. I'm using ngk bp7es plugs which have been fine before, gapped at 0.8mm. Thanks

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    Re: xflow knocking/rattling noise

    It sounds like you are firing in the wrong order...you could be 180 degress out....thats where i would start...cheers mark

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    Re: xflow knocking/rattling noise

    firing order is unusual, it's 1-2-4-3

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    Re: xflow knocking/rattling noise

    Am i right in thinking that as i left the dizzy alone, only removed cap and replaced back in same place that the timing should be ok? Would any of the timing be messed around by what ive done removing engine? I shall hopefully get time again soon to get out and have another tinker.

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    Re: xflow knocking/rattling noise

    Quote Originally Posted by upthevilla View Post
    Am i right in thinking that as i left the dizzy alone, only removed cap and replaced back in same place that the timing should be ok? Would any of the timing be messed around by what ive done removing engine? I shall hopefully get time again soon to get out and have another tinker.
    theres no guarantee it will be in the correct position...check when all your timing marks are in align and the piston is at top dead centre..that the rotor arm is pointing at no1 spark plug lead position...its a quick way to rule this problem out...

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    Re: xflow knocking/rattling noise

    Got on it again yesterday, all running nicely now. Don't ask why it was running rough, no idea. Fiddled with cap, leads, plugs, etc, no difference then after cuppa tea went out and she fired up lovely. Was a bit tappety so adjusted them and all nice now. Thanks to everyone for replies and suggestions. Cheers.

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