Engine knock, HELP! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Ericram · 08-14-2011, 04:19 PM

bad knocking sound coming from inside block it seems. I thought was a loose vavle/rocker at first but def not after removing both valve covers. truck actually runs fine as in not missing or loping however is a really bad knock almost clacking sound. if would be a piston issue wouldnt truck be missing a little? Any sugestions would be greatly appreciated. Tomorrow i will be taking it to my uncles mech shop to get further into issue.
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GASoline71 · 08-14-2011, 04:23 PM

Rod knock is on the big end of the rod at the crank. Spun bearing. The longer you run it, the more damage is being done. A rod knock will dissappear slightly under power, and then get very loud as you come off the pedal. Will also be a constant at idle.

Gary

Ericram · 08-14-2011, 04:41 PM

Thanks for the quick reply, the knock seems to be very inconsistant. not very loud at idle but def can hear it and when you press on gas it gets louder. Spun bearing would cause this type of issue? i hope it is that b/c i dont imagine that hurting my wallet too much as far as parts right?
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GASoline71 · 08-14-2011, 04:44 PM

A spun bearing is a complete engine teardown and rebuild... so it hits the wallet pretty hard.

So it does it when the engine is under power?

Gary

Ericram · 08-14-2011, 04:51 PM

Yes, the knock/clack gets much louder under power. what really throws me off is it starts n idles fine minus he very loud knock.i literally thought there was a loose bolt or something just being knocked around when the sound started. I will see if i can fgr out how to post a quick video in hopes of you being able to hear it. I really appreciate your help so far.
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rsavage · 08-14-2011, 05:00 PM

If it is a spun bearing, you will need to rebuild the bottom end, more than likely requiring machining of the crank (engine pulled from truck). Not an inexpensive fix. If you are going to do that and the rings, pistons and bores are okay, you might as well change the cam, timing gears, chain, oil pump and lifters unless they are realatively new. Cam, lifters, timing set, oil pump, install lube, cam break in lube, full felpro gasket set can be had from Summit for about $200 if you use their brand. Bearings an machine work on the crank will be more. You will have to see how much the crank has to be cut to know what size bearings you will need. Good learning experience for you if your Uncle can assist you.

Ericram · 08-14-2011, 05:34 PM

85 chevy 350 engine knock - YouTube

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eightbanger · 08-14-2011, 05:55 PM

Would a lobe have gone on the cam, or maybe a stuck lifter?
Or damaged push rod.

It doesn't sound like bottom end noise.

BIGKEV · 08-14-2011, 06:25 PM

Check your torque converter bolts!

**JDL** · 08-14-2011, 07:09 PM

Looks like it is internal there is no oil come from the push rods

Phorbes · 10-15-2017, 12:16 PM

Did you ever find out what the problem was? I have a similar sound where it’s inconsistent but it goes away under load.

08-14-2011, 04:19 PM	#1
Ericram Registered User Join Date: Dec 2009 Location: Fort Worth , Texas Posts: 27	Engine knock, HELP! bad knocking sound coming from inside block it seems. I thought was a loose vavle/rocker at first but def not after removing both valve covers. truck actually runs fine as in not missing or loping however is a really bad knock almost clacking sound. if would be a piston issue wouldnt truck be missing a little? Any sugestions would be greatly appreciated. Tomorrow i will be taking it to my uncles mech shop to get further into issue. Posted via Mobile Device

08-14-2011, 04:41 PM	#3
Ericram Registered User Join Date: Dec 2009 Location: Fort Worth , Texas Posts: 27	Re: Engine knock, HELP! Thanks for the quick reply, the knock seems to be very inconsistant. not very loud at idle but def can hear it and when you press on gas it gets louder. Spun bearing would cause this type of issue? i hope it is that b/c i dont imagine that hurting my wallet too much as far as parts right? Posted via Mobile Device

08-14-2011, 04:51 PM	#5
Ericram Registered User Join Date: Dec 2009 Location: Fort Worth , Texas Posts: 27	Re: Engine knock, HELP! Yes, the knock/clack gets much louder under power. what really throws me off is it starts n idles fine minus he very loud knock.i literally thought there was a loose bolt or something just being knocked around when the sound started. I will see if i can fgr out how to post a quick video in hopes of you being able to hear it. I really appreciate your help so far. Posted via Mobile Device

08-14-2011, 05:00 PM	#6
rsavage Registered User Join Date: Aug 2009 Location: Alden NY Posts: 2,705	Re: Engine knock, HELP! If it is a spun bearing, you will need to rebuild the bottom end, more than likely requiring machining of the crank (engine pulled from truck). Not an inexpensive fix. If you are going to do that and the rings, pistons and bores are okay, you might as well change the cam, timing gears, chain, oil pump and lifters unless they are realatively new. Cam, lifters, timing set, oil pump, install lube, cam break in lube, full felpro gasket set can be had from Summit for about $200 if you use their brand. Bearings an machine work on the crank will be more. You will have to see how much the crank has to be cut to know what size bearings you will need. Good learning experience for you if your Uncle can assist you. __________________ 1961 C1 Corvette 1959 El Camino 350 TPI, 9" 4 w disc 69 Blazer K5 - sold July '20 2021 Durango RT 5.7

08-14-2011, 05:55 PM	#8
eightbanger 454 MAKES IT ROAR Join Date: Jan 2008 Location: Essex, U.K Posts: 2,701	Re: Engine knock, HELP! Would a lobe have gone on the cam, or maybe a stuck lifter? Or damaged push rod. It doesn't sound like bottom end noise. __________________ Nigel. An American living in a British body. 1971 Chevy Cheyenne 10 454 "In a time of universal deceit, telling the truth becomes a revolutionary act." - George Orwell "When injustice becomes law, resistance becomes duty" - Thomas Jefferson No more pain. 03.12.60 -- 12.28.10 http://www.youtube.com/Eightbanger Last edited by eightbanger; 08-14-2011 at 06:03 PM.

08-14-2011, 06:25 PM	#9
BIGKEV Registered User Join Date: Jan 2011 Location: Prescott AZ Posts: 112	Re: Engine knock, HELP! Check your torque converter bolts!

08-14-2011, 07:09 PM	#10
JDL Senior Member Join Date: Sep 2000 Location: Agency IA. Posts: 1,848	Re: Engine knock, HELP! Looks like it is internal there is no oil come from the push rods __________________ 72 Chevy short step side with 454 air and tilt. 72 nova project car 63 chevy II drag car Agency Iowa

10-15-2017, 12:16 PM	#11
Phorbes Registered User Join Date: Jun 2017 Location: Austin TX Posts: 12	Re: Engine knock, HELP! Did you ever find out what the problem was? I have a similar sound where it’s inconsistent but it goes away under load.



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