Can't find bearing noise

Road-race engines and ancillaries - general discussion
AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Sat Oct 25, 2014 4:02 am

Thanks!
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tmvolumex
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Re: Can't find bearing noise

Post by tmvolumex » Tue Oct 28, 2014 7:10 pm

Csaba,
I bet you have a plastic auxiliary shaft pulley installed or a plastic intake or exhaust cam pulley installed and that is the source of the noise.
The center steel core of the plastic pulley gets loose with thermal cycling and stress and makes a sound like a rod knock or loose belt cover etc.
Because of the pulleys age, the fit of the steel center core is loose and dependent on temperature. You may notice that the noise comes and goes with variations in temperature.
Get rid of the plastic pulleys. You can grab the pulley and try to rotate it back and forth and feel the loose fit of the steel center core.
Tom
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Tue Oct 28, 2014 7:32 pm

Tom your posts are always welcome but with respect I do not agree (in general).

If the big spoked steel hub in the plastic pulley is secure there is no reason to suspect it.

G
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tmvolumex
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Re: Can't find bearing noise

Post by tmvolumex » Tue Oct 28, 2014 9:44 pm

Guy,
I had a noisy plastic pulley as I described, I swapped it out and the noise was eliminated. The metal core was loose inside the over molded assembly.
I think with all the other things Casaba checked and did not find the cause, he should check any plastic pulleys, especially since they are from the 19070's.
Tom
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Wed Oct 29, 2014 10:36 am

it's ok Tom, I am not doubting you at all,

I just don't want folk pulling off their plastic pulleys or refusing to use them per-se.

It happens that the plastic rear-flanged one is one of the few with the right offset for the 1" belt conversion..

G
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tmvolumex
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Re: Can't find bearing noise

Post by tmvolumex » Wed Oct 29, 2014 3:30 pm

Guy, no worries.
Yes, the plastic pulleys are light weight and work for the auxiliary shaft application. I think the best way to find the source of noise related problem is with a stethoscope. For the plastic pulley noise, I found its best to remove the diaphragm and metal rod from the stethoscope and just hunt around with the open stethoscope hose. The noise emanates from the plastic portion of the pulley and is not easily transmitted and or located if you are checking on the engine block.
Tom
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Tue Nov 11, 2014 6:47 am

I have checked the plastic aux pulley visually and it looked fine, but I may have to pull the belt off and do a more thorough check.

FWIW I drove the car ~350 miles last weekend and noise did not change.
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Tue May 19, 2015 2:16 am

OK, I found it. It's really stupid. I am running a slightly smaller diameter crank pulley and the ribs on the inside of the V-belt were slightly touching the timing belt pointer. When running these ribs become invisible, so it did not look like they were touching. The new V-belt must have been just a bit 'deeper' than the ones I ran before. This would explain why the noise was loudest when listening to the seal carrier - the pointer is bolted to it.

I'm glad it was not anything more serious, although I had quit worrying about as it made the noise for so long, and I had checked so many things I was sure the engine was in good shape.

Csaba
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Will01
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Re: Can't find bearing noise

Post by Will01 » Tue May 19, 2015 11:18 am

Good job, these things just have to ne investigated sometimes even when it drives you mad. Well done for perservering
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