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Old 02-14-2004, 09:56 AM
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engine knocking

I own a chevy impala with a 283 powerglide setup w/2 barrel carb. The engine is making a very loud knocking noise coming from or around the #8 piston area. This noise is very evident around 500 rpm and goes away little by little until bout 1100 1200 rpm where the noise is gone completly. I tried adjusting the valves at the #8 cylinder and (engine at about 700 rpm, noise still very evident) the noise got louder a little and backed it back off where it was and went back to the original loud noise. I don't know if the timing chain skipped a tooth or the cam and or lifters are getting bad? oh yeah this 283 has about 102,000 original miles on it.

Thanks for all the input.

Nick

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Old 02-14-2004, 10:36 AM
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Does the noise go away at all as the engine warms up?

Try pulling off spark plug wires one at a time until the noise goes away. What this does is take the load off the piston.
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Old 02-14-2004, 10:52 AM
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Are you sure you don't have a broken rocker arm or a bent pushrod?
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Old 02-14-2004, 05:30 PM
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What about a bad rod or main bearing?
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Old 02-14-2004, 06:01 PM
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Hi,
I also have the 283 in the other post about gas mileage. My engine has knocked bad for years. The only way to quiet it down is to put 20W-50 oil in it and then add two or even 3 cans of Bardall 2 (the really thick gooey stuff). This makes it quiet. And its worked for nearly 5 years and 40,000 miles that way. But now my engine is finished (probably has 150,000 miles on a mediocre rebuild). Short of taking it all apart its the only thing to do...
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Old 02-14-2004, 06:09 PM
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Marvel Mystery oil can help in those situations too.
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Old 02-14-2004, 09:03 PM
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Maybe a stuck/collasped lifter? Since adjusting the rocker arm changed the sound it would seem it is valve train related. Is it a knock or a tap?

If you do what lluciano77 suggested (remove 1 wire at a time) and the noise does not go away it could be a lift or something like that. If the noise does go away you probably have a bad bearing, or wrist pin/bore.

Royce
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Old 02-14-2004, 09:19 PM
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If it is a bearing or rod nock the noise won't quiet down as the engine warms up. If it does quiet down it is a collapsed piston.
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Old 02-15-2004, 08:02 AM
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You could also have a broken skirt on the piston. If you get ambitious pull the pan and see if anything is laying in it.
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Old 02-17-2004, 10:05 PM
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Well after minor dismantling I moved the crank pulley back and forth and noticed there was some slack at the flywheel. The torque converter bolts were looser than a...well you know.
Its funny the sound of loose converter bolts are very similar to a rod or main bearing going out.

Thanks for all of your input I appreciated it.
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Old 02-17-2004, 10:37 PM
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Cool! I'm glad it was an easy fix.

I had a collapsed piston recently that wasn't quite and easy fix. It involved a complete tear down and replacement of one piston. That sucked!
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