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02-23-2003, 02:03 AM
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#1 |
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Garage Queen Material
Join Date: Oct 2002
Location: USA
Posts: 4,129
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knocking sound?
whenever my truck is cold and i just start it and let it warm up, i have to keep my foot on the gas for a minute to make sure it doesnt die. well whenever i blip the gas softly when its cold like that(never going above 1500 rpm's) the engine makes a loud knocking sound that i do not know what it is.
hopefully its a rod trying to push its way through the side of the block  it wants to be replaced by new faster engine |
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02-23-2003, 11:03 AM
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#2 |
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Genuine Chevrolet
Join Date: Feb 2003
Location: South West Pennsylvania.
Posts: 582
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You might be getting your wish (hoping rod trying to push it's way through side of block), but because it goes away as it warms up I would go with your headers leaking a bit. As the metal heats, it expands and after a short while the leak seals and the knock goes away. I beleive a rod would knock more as the oil warms up and gets thinner.
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George 82 Silverado LWB 4x4 350 SM465 NP208 77 Chevrolet Blazer Chalet 400 TH350 NP203 |
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02-23-2003, 01:31 PM
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#3 |
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Garage Queen Material
Join Date: Oct 2002
Location: USA
Posts: 4,129
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headers should not be leaking. and the sound is coming from the bottom of the engine, and i know its not the collectors because i replaced the gaskets about 2 weeks ago.
i do not know if it has anything to do with my cracked flexplate though. |
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02-23-2003, 01:43 PM
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#4 |
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Registered User
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 22,066
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ocbaud, I've got the same thing going on w/my 74's 350. Sounds like a diesel when I first start-up on cold am's but after warm-up it goes away (or @ least it's undetectable). It's odd that it goes away so I'm debating whether or not to tear into it.
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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02-23-2003, 03:07 PM
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#5 |
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~THE SILVER BULLET~
Join Date: Oct 2002
Location: WYOMING
Posts: 285
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the reason it goes away when it warms up is because metal expands as it gets hotter. you possibly have a piston slapping against the side of the cylinder walls(i think that is the problem on the new chevys) but as it warms up clearances get tighter and there is no room for it to wobble around. possibly worn rings? just my thoughts...
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~1980 c10 chevy scottsdale~ ~2.5/4 drop 305/th350c~ |
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02-23-2003, 05:37 PM
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#6 |
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Registered User
Join Date: Feb 2003
Location: Edmond, Oklahoma
Posts: 425
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THIS SEEMS TO BE A PROBLEM WITH ALL OLD HIGH MILAGE ENGINES. WHEN I HAD MY 305 IT WOULD ALWAYS DO THAT IT WAS REALY ANNOYING. IT'S JUST SOMETHING YOUR GUNNA HAVE TO DEAL WITH TILL YOU GET SOME MONEY FOR A NEW ENGINE.
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84 Chevy Stepside, 350, TH350, 268h Comp cam, Hooker headers, MSD Pro Billet, Edelbrock Performer manifold and 1604 carb, 40 Series Flowmasters dumped, and Western Chassis 3/5 drop w/ c notch. New 3:73 Eaton Posi |
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02-23-2003, 06:04 PM
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#7 |
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Registered User
Join Date: Apr 2001
Location: DALLAS,TX
Posts: 22,066
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I thought it was prob the rings but when I did a compression test it had between 155-165 psi on all 8cyl. so that's what what was weird. I would think one cyl @ least would have lower psi than the others or all of them would be lower psi than a 160psi average (from what I've heard, 160 is pretty good).
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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02-23-2003, 11:14 PM
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#8 |
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LED King
Join Date: Jan 2003
Location: Sacramento, CA
Posts: 2,087
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My 305 does the same, but it might just be my muffler w/ a hole in it. It wants to be replaced with a flowmaster! (I just want sound ok) Whenever I get the money... and remember what to spend it on... WHAT IS IT WITH PEOPLE AND CAPS???
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Tyler 1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles 2006 Ford Focus ZX3 5-speed Stick 2016 Chevy Spark EV Gone: 2002.5 VW GTI 24v VR6 Gone: 2008 VW R32 |
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02-24-2003, 02:05 AM
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#9 |
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Account Suspended
Join Date: Oct 2002
Location: Elkhart, IN
Posts: 6,399
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Eric, you have a known cracked flexplate, correct? if so, that is probably your knocking sound. replace it, and it should go away.
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02-24-2003, 05:54 PM
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#10 |
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~THE SILVER BULLET~
Join Date: Oct 2002
Location: WYOMING
Posts: 285
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scoti, was the engine hot or cold when you did the compression test? if it was warm then the metal was expanded, thus solving the problem. try it cold
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~1980 c10 chevy scottsdale~ ~2.5/4 drop 305/th350c~ |
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02-24-2003, 08:27 PM
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#11 |
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BeWarE tHe eViL CrAnkTOe!
Join Date: Oct 2002
Location: Yukon, OK
Posts: 3,605
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hope you get it fixed soon.
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~Dave~ You can call me Mike, Mike Oxlong - 1986 Chevy SWB - Stock for now - 1986 Chevy Custom SWB *Stolen 6/26/05* - 1985 Chevy SWB SOLD - 1999 T/A Some mods  www.cardomain.com/id/ramairdave AIM Screenname - Jester84 |
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02-24-2003, 08:31 PM
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#12 | |
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Garage Queen Material
Join Date: Oct 2002
Location: USA
Posts: 4,129
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