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i just replaced the main and rod bearings because of a knock. its still there. it sounds like a moderate to hard aluminum tap. it use to occur only at 2000 rpm and above but never at idle or below 2k rpm. over time it also started to slowly progess lower to starting at 1700 rpm. it went away for a couple days but now its back and it moved, it now taps at 2500 and above. it is definately an aluminum knock. would jumped timing cause this? jumped a tooth or something? computer not adjusting correctly? i am totally at a loss. any help would be appreciated.
 

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Madd Tyte JDM yo ®
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7,014 Posts
well, try to verify if it comes from the bottom end or closer to the top end. its possible that there is a worn valve guide or that the shims are out of spec and too loose. if its a LIGHT knock like someone is tapping on the intake manifold w/ a screwdriver, its most likely top end noise. if its a louder deeper tapping like tapping a socket wrench or hammer on the block, its bottom end noise like rod knock.
 

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(╯°□°)╯︵ ┻━┻
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tapping, jumping timing..... sounds like you've got a bad crank keyway.

take off the harmonic balancer and timing gear and see if the keyways are wiped out, along with the crank snout and gear...
 

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Not ur jizz, not ur bizz
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Tanya said:
tapping, jumping timing..... sounds like you've got a bad crank keyway.

take off the harmonic balancer and timing gear and see if the keyways are wiped out, along with the crank snout and gear...
yeppers..either that or loose cank pulley.
 

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Verrrry nice!
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302 Posts
He didn't say it jumped timing, hes asking if jumped timing could cause the noise, i wouldnt pull the balancer. Easy enough to pull the top cover and check timing though. Mine was doing the same thing at one time after drag racing , come and go, diff rpms etc, turned out i had 2 valve seats popped out! Check your valve clearances and look at the vales with a boroscope.
 

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Boost is my drug!
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1,319 Posts
definitely a valve lash misadjustment or loose.


I had the same sistuation before when it was tapping real bad in the back end of the head and after i had my head done, i realized that I had mixed the valve seats or lashes as u call them, i had to use caliper and measure to find which is intake and exhaust then after that I measured each lashes to find the difference in each valves and found my way around it and set it back in and it went away. very smooth and light tapping on front as typical situatiions occur like that and usually it comes from the injector clicking noises.

just my .02
 
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