Knocking!
Tech Contributor
Joined: Mar 1999
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From: Northern VA
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Remove the belts and start it......if the noise goes away....it is the main bearings.
If not...it is either piston related, rod related or valvetrain.
Pull valve covers and check for broken rocker.
Pull oil pan to verify rods of course.
Good luck to you.....never a good scene when something is knocking.
Jebby
If not...it is either piston related, rod related or valvetrain.
Pull valve covers and check for broken rocker.
Pull oil pan to verify rods of course.
Good luck to you.....never a good scene when something is knocking.
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
On the mains....belt tension on a loose main journal can amplify noise....
If you determine the bearings are bad.....then you need to remove it and repair or replace.....
I hope that clears it up a bit.
Jebby
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You or somebody needs to wiggle each rod on its journal for slop. If there is....that is the noise.
On the mains....belt tension on a loose main journal can amplify noise....
If you determine the bearings are bad.....then you need to remove it and repair or replace.....
I hope that clears it up a bit.
Jebby
On the mains....belt tension on a loose main journal can amplify noise....
If you determine the bearings are bad.....then you need to remove it and repair or replace.....
I hope that clears it up a bit.
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
One of the best pieces of print known to Chevy-dom:
http://www.amazon.com/How-Rebuild-Your-Small-Block-Chevy/dp/1557880298
Get this and read it.....my father bought me a copy when I was 11-12 years old
It will tell you pretty much what you need to know so you can tackle your problem armed with knowledge.
Jebby
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Burning Brakes
Joined: Nov 2005
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From: Cartersville GA
You could use an old trick, get a piece of garden hose or similar (heater hose) and with the engine running hold one end to your ear and place the other on the valve covers moving front to back. If one of the rockers is knocking, you should be able to get close to it without pulling the covers. If you hear the knock, move to the intake runner on the side with the knock and using the hose set it on each intake runner. If one is louder, check the rockers on that piston. It also could be a stuck lifter, or fuel pump push rod. Does it knock once per engine revolution or more?
Melting Slicks
Joined: Apr 2009
Posts: 2,632
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From: Great Plains Iowa
You could use an old trick, get a piece of garden hose or similar (heater hose) and with the engine running hold one end to your ear and place the other on the valve covers moving front to back. If one of the rockers is knocking, you should be able to get close to it without pulling the covers. If you hear the knock, move to the intake runner on the side with the knock and using the hose set it on each intake runner. If one is louder, check the rockers on that piston. It also could be a stuck lifter, or fuel pump push rod. Does it knock once per engine revolution or more?
I keep a 6 foot length of 1/2" low pressure hydraulic hose for siphoning fuel and for listening for the source of noises. When it comes to finding the source of a noise NOTHING beats a hose held up to your ear and I've been using one for 50 years.
Drifting
Joined: Jun 2005
Posts: 1,950
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From: Chino Hills CA
I've been using a large screwdriver with the handle end as the earpiece. That being said, rod knocks are rare on small block Chevy's and main bearing knocks are even rarer. Valve train noises are much more common. Worn main bearings are a very deep and thudding type sound, rod knocks are crisper and get louder when you take your foot off the gas, no load. Piston slap, (worn rod small ends and wrist pins) are tinnier. But a more likely suspect is a bad lifter, valve, guide, rocker, or bent pushrod. Just my $.02 cents.
Melting Slicks
Joined: Jun 2006
Posts: 2,071
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From: S Nevada
I have to laugh, I recall carpooling with a kid from A&P school some 30 odd yrs ago. We heard a knocking sound, hmm whats that, then a major ugly loud bang. That was the rod coming out the side of the block.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Main bearings are more of a deep rumbling noise.
Rod bearings are a knock knock consistent with the RPM.
Valve train is more of a sharp clack clack or clickity clack noise.
Any of those sound familiar?
Rod bearings are a knock knock consistent with the RPM.
Valve train is more of a sharp clack clack or clickity clack noise.
Any of those sound familiar?
Race Director
Joined: Jul 2015
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From: SW Florida.
do not attempt this alone. everybody's first attempt at self-taught crank work ends in noisy disaster. you may get away with replacing rods and mains, but these aren't cars we drive around at low throttle. they won't last. you need an engine. or a rebuild.
Thread Starter
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ok sorry it took me a while to respond. the oil level is fine just recently replaced it. the old oil was smooth didnt have any grit too it. like i said just had the transmission worked on so i will check for loose bolts. i did pull off spark wires and the noise did not go away. also the noise is most loud near the rear of the engine.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
ok sorry it took me a while to respond. the oil level is fine just recently replaced it. the old oil was smooth didnt have any grit too it. like i said just had the transmission worked on so i will check for loose bolts. i did pull off spark wires and the noise did not go away. also the noise is most loud near the rear of the engine.
Jebby