sources of engine knock? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

robert2323 · 02-12-2010, 02:38 PM

1969 Chevy C20 with GM Goodwrench 350. Frustrating situation. Bought a remaned distributor, installed it and when I fired it I had an extremely loud engine noise. Sounded like a sledge hammer banging against steel. Diagnostics being my weak suit, I assumed rod knock. Pulled pan and checked my bearings. No metal flakes anywhere, found one bearing with the slightest of play. The bearing had a wear spot in it, so repaced it. I installed everything back togheter, new oil (10w30) and filter and fired again. Still loud knock. The parts guy at Kragen said there was no way that distributor would make a loud knock. Being baffled, I've pulled heads to look for broken piston, but nothing obvious there either. I have a friend giving me a chevy 350 distributor today (after buying a head set and reinstalling top end). Any advice would be graciously welcome, because I'm at a loss, feeling like a jackass taking apart a perfectly good long block.

cableguy0 · 02-12-2010, 02:59 PM

Things can resonate through the engine. If the distributor has a bunch of play or a loose gears it can knock and will carry right through the engine. you need to locate the source of the knock. get a long screwdriver or a piece of heater hose and listen to the engine to find where the noise is loudest and at least you will have a general area to look in. Most of the parts in the engine can create a knocking noise under the right conditions. Just so im straight the engine was quiet before? You replaced the distributor and the knock started? Obviously you wanna go for the part that was changed first as the source. Most parts guys are selling parts because they cant hack it spinning wrenches. Most of the advice that comes from behind the counter should definately be taken with a grain of salt. The water pump,balancer, power steering pump can all knock as well. A Loose timing chain will also cause a knock. Loose wrist pin,broken piston skirt. cracked piston,rod& main bearings. flexplate/torque converter.

cdowns · 02-12-2010, 03:30 PM

was the engine running without knock prior to dizzy installation?

MacAttack · 02-12-2010, 03:53 PM

Quote:

Originally Posted by cableguy0

Most parts guys are selling parts because they cant hack it spinning wrenches. Most of the advice that comes from behind the counter should definately be taken with a grain of salt.

Truer words have never been spoken.

02-12-2010, 02:38 PM	#1
robert2323 Registered User Join Date: Nov 2009 Location: Redding, CA Posts: 1	sources of engine knock? 1969 Chevy C20 with GM Goodwrench 350. Frustrating situation. Bought a remaned distributor, installed it and when I fired it I had an extremely loud engine noise. Sounded like a sledge hammer banging against steel. Diagnostics being my weak suit, I assumed rod knock. Pulled pan and checked my bearings. No metal flakes anywhere, found one bearing with the slightest of play. The bearing had a wear spot in it, so repaced it. I installed everything back togheter, new oil (10w30) and filter and fired again. Still loud knock. The parts guy at Kragen said there was no way that distributor would make a loud knock. Being baffled, I've pulled heads to look for broken piston, but nothing obvious there either. I have a friend giving me a chevy 350 distributor today (after buying a head set and reinstalling top end). Any advice would be graciously welcome, because I'm at a loss, feeling like a jackass taking apart a perfectly good long block.

02-12-2010, 02:59 PM	#2
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: sources of engine knock? Things can resonate through the engine. If the distributor has a bunch of play or a loose gears it can knock and will carry right through the engine. you need to locate the source of the knock. get a long screwdriver or a piece of heater hose and listen to the engine to find where the noise is loudest and at least you will have a general area to look in. Most of the parts in the engine can create a knocking noise under the right conditions. Just so im straight the engine was quiet before? You replaced the distributor and the knock started? Obviously you wanna go for the part that was changed first as the source. Most parts guys are selling parts because they cant hack it spinning wrenches. Most of the advice that comes from behind the counter should definately be taken with a grain of salt. The water pump,balancer, power steering pump can all knock as well. A Loose timing chain will also cause a knock. Loose wrist pin,broken piston skirt. cracked piston,rod& main bearings. flexplate/torque converter. __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

02-12-2010, 03:30 PM	#3
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: sources of engine knock? was the engine running without knock prior to dizzy installation? __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY



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