Knocking when the car warms up?
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,078
Likes: 0
From: Santee CA
Knocking when the car warms up?
I've started noticing a knocking sound when the car warms up, coming from the passenger side of the engine.
I seriously doubt it's bad plugs, or plug wires, because those have just been replaced.
I've got 91 octane gas running through it right now, and the car didn't have this problem the last few times I drove it. I DID kind of play with the fuel mixture a bit before the knocking started because I'm still having problems with the car not having any power. However, I don't get why it would just start knocking on the right side only, and only do it when the car warms up...I don't know what would be causing the knock, exactly. I'm going to try to do some timing on it this weekend, along with carb adjustment per Lars' Q-Jet tuning paper.
Anyone have any thoughts?
I seriously doubt it's bad plugs, or plug wires, because those have just been replaced.
I've got 91 octane gas running through it right now, and the car didn't have this problem the last few times I drove it. I DID kind of play with the fuel mixture a bit before the knocking started because I'm still having problems with the car not having any power. However, I don't get why it would just start knocking on the right side only, and only do it when the car warms up...I don't know what would be causing the knock, exactly. I'm going to try to do some timing on it this weekend, along with carb adjustment per Lars' Q-Jet tuning paper.
Anyone have any thoughts?
Melting Slicks
Joined: Sep 2004
Posts: 2,412
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Melting Slicks
Joined: Nov 2000
Posts: 2,663
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From: Palm Harbor FL
I would seriously check your valve/lifter/rocker arm/cam lobe on that side. With it only being on the one side, it's unlikely it is fuel/mixture related. Could be a sticking valve, a rocker arm adjustment, a failing hydraulic lifter or worst case scenario, a worn cam lobe.
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,078
Likes: 0
From: Santee CA
Originally Posted by 79MakoL82
I would seriously check your valve/lifter/rocker arm/cam lobe on that side. With it only being on the one side, it's unlikely it is fuel/mixture related. Could be a sticking valve, a rocker arm adjustment, a failing hydraulic lifter or worst case scenario, a worn cam lobe.
I'm hoping it's just rocker arm adjustment that needs to be done...The previous owner blew a head gasket before we got the car, and left it sitting. My dad said he adjusted the rocker arms before the car was ever started, but now I'm not so sure.
Drifting
Joined: Jul 2005
Posts: 1,562
Likes: 2
From: Spring Texas
Originally Posted by Sprzout
I seriously doubt it's bad plugs, or plug wires, because those have just been replaced.
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Before you do anything make sure its the engine that's making the noise. You may have something as simple as an exhaust pipe banging against the crossmenber. Get a piece of aluminum or steel tubing about 1/8 inch by 12 inches. Put a vacuum hose on it and use it as a stethescope. You'll soon find exactly where the noise is coming from. Good luck.
Instructor
Joined: Mar 2006
Posts: 242
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From: Cumming GA
I dont know if this applies to yours. But isn't the passenger side where the warmup valve assembly is (between exhaust manifold and downpipe), and when they get a bit weak, they kinda flap around and are noisy until the engine warms up enough to keep it full open and tight?
Last edited by kaamacat; Apr 6, 2006 at 05:43 PM.
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Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,078
Likes: 0
From: Santee CA
Originally Posted by kaamacat
I dont know if this applies to yours. But isn't the passenger side where the warmup valve assembly is (between exhaust manifold and downpipe), and when they get a bit weak, they kinda flap around and are noisy until the engine warms up enough to keep it full open and tight?
That happened to my 80 ,10 days after I got her,hope it's not the same problem,but mine was bad main bearings,had the motor rebuilt!
Pro
Joined: Dec 2005
Posts: 675
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From: Kinzers. PA
Ummm if you havnt fixed it yet... Check your heat riser valve, it mite of broke and is just flapping now. Then once it warms up it starts to bang around instead of sit there open.....
Its just my guess Try it and let me know.... Its the passanger side, and knocks check it cant hurt you.
Its just my guess Try it and let me know.... Its the passanger side, and knocks check it cant hurt you.
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,078
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From: Santee CA
Originally Posted by frostbitten09
Ummm if you havnt fixed it yet... Check your heat riser valve, it mite of broke and is just flapping now. Then once it warms up it starts to bang around instead of sit there open..... Its just my guess Try it and let me know.... Its the passanger side, and knocks check it cant hurt you.
Its just my guess Try it and let me know.... Its the passanger side, and knocks check it cant hurt you.Already replaced it...
Burning Brakes
Joined: Aug 2005
Posts: 1,126
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From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by vettfixr
Before you do anything make sure its the engine that's making the noise. You may have something as simple as an exhaust pipe banging against the crossmenber. Get a piece of aluminum or steel tubing about 1/8 inch by 12 inches. Put a vacuum hose on it and use it as a stethescope. You'll soon find exactly where the noise is coming from. Good luck.
Last edited by kb2fzq; Apr 7, 2006 at 06:15 AM.
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,078
Likes: 0
From: Santee CA
I found the problem.
It's a worst case scenario deal; the valves are knocking, and there's piston slap going on in the block.
So much for driving the Vette this summer...It's gonna need an engine rebuild, as it's just gonna get worse. Apparently, the valves are knocking and there's also a rod bearing that's bad, from what my dad can surmise...
It's a worst case scenario deal; the valves are knocking, and there's piston slap going on in the block.
So much for driving the Vette this summer...It's gonna need an engine rebuild, as it's just gonna get worse. Apparently, the valves are knocking and there's also a rod bearing that's bad, from what my dad can surmise...