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race car vibration
Home away from home
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2002/6/18 21:09
From NSW South Coast
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anyone got any ideas . I have got a realy bad vibration coming from my a15 whenever i rev it over about 6500 rpm. I know its coming from the motor as ive changed the gearbox before the last event and its not speed related just revs. I can get it to do it while in neutral. It just came all of a sudden.
Could it be a tuning problem, I'm going to disconect the fan belt .water pump, alternater this weekend and see if its there. I had to drop the sump off the other day but I didn't find anything anusual or lose.
any help would be apreciated.

Posted on: 2002/10/23 21:20
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Re: race car vibration
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2002/8/12 21:51
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Seems a bit odd, vibration usually decreases with higher rpms. Run a compression check on each pot, it might give you an indication on a piston binding or a gudgon pin bearing on the way out.

Rip your rocker cover off and check your valve springs and tappets, if you've got a broken one, at high rpm you might be bouncing a valve of the top of a piston.....yuck, I know.

Micko

Posted on: 2002/10/23 22:26
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Re: race car vibration
No life (a.k.a. DattoMaster)
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The waterpump alternator belt is a good idea.

I'd also be checking that the flywheel and clutch are all in good order.

The fact that you don't get it in neutral means it's load related..

I was thinking maybe a misaligned/damaged clutch or loose flywheel bolts (scary). Could it be a broken clutch diaphram spring? Again probably not, as you don't get the vibration in neutral.

Are your universal joints in the tail shaft good?? Are the balance weights still attached? Look for fresh paint or clean metal, indicating a missing balancing weight. These are normally spot welded on.

This is more likely.

Cheers,
Chris.

ps. My old A12 only revved to 6600rpm before valve bounce...So if you say yours is only vibrating above 6500, then you are really pounding the poor old A-series.


Posted on: 2002/10/23 22:53
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Re: race car vibration
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sorry it DOES it in neutral so its nothing to do with the tailsharft etc the valve springs are only fairly new so I'll look at them . I usually rev it to 8000rpm as its been balanced and has duel valve springs. I've seen a15s flywheels come lose so I checked that when I changed the gearbox It was ok
It seems to have just as much power as usual so i'm hoping its something simple like waterpump or something like that

thanks

Posted on: 2002/10/23 23:48
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Re: race car vibration
No life (a.k.a. DattoMaster)
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2002/7/19 12:41
From sydney australia
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what sort of a sump do you have on the girl.is it an a15 with the scallops(not seafood or potato cakes) on the side for rod clearance.i've got an a14 sump on my a15,which seems to do the same thing at revs,so while the clearances might be right at idle,the crank might be rubbing against the sump.also,what about the front pulley,was it balanced with the motor when you built it.

Posted on: 2002/10/24 10:28
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Would it be possible to get a late model Nissan Micra, fit the 1.8 litre motor from a Tiida & then turbocharged it? Your answer must include parts numbers for the conversion. You have 12 months. Commence.
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Re: race car vibration
No life (a.k.a. DattoMaster)
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sounds to me like flywheel or clucth problems I have had the same happen to me its a weird feeling.
cheers Andrew

Posted on: 2002/10/24 12:13
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Re: race car vibration
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The sump is an a15 that I'v been using for years.No problem. the pulley was balanced with everything else and the flywheel and clutch all look and feel ok. The vibration doesn't build up it just switches on weird!
I'll keep looking
thanks

Posted on: 2002/10/24 20:55
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Re: race car vibration
No life (a.k.a. DattoMaster)
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Another pointer maybe the bolt that holds the alternator bracket on may be broken or loose this has also happened to me. Also the front pulleys can crack on the keyway (on crankshaft)and rattle.
hope you find it Cheers Andrew

Posted on: 2002/10/25 11:52
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