Valves knocking like crazy, what causes?
Thread Starter
Former Vendor
Joined: Feb 2002
Posts: 7,812
Likes: 3
From: DFW, TX www.vettestripes.com
St. Jude Donor '03-'04-'05-'06-'07-'08
Valves knocking like crazy, what causes?
I got the car tuned in Winter so I did not run the car with AC on.
Now in summer, when I turn on AC, the valves're knocking really loud when run under 2200 RPM.
That brings me more attention so I also notice the valves are also knocking w/o AC turned on as well but just not as loud and bad when AC's on.
What might cause it? Bent valves? Bad tune?
My car is MN6 with G5X-2 cam.
Thanks in advance for your help.
-Mike
Now in summer, when I turn on AC, the valves're knocking really loud when run under 2200 RPM.
That brings me more attention so I also notice the valves are also knocking w/o AC turned on as well but just not as loud and bad when AC's on.
What might cause it? Bent valves? Bad tune?
My car is MN6 with G5X-2 cam.
Thanks in advance for your help.
-Mike
Le Mans Master
Joined: Nov 2002
Posts: 7,179
Likes: 2
From: Charlotte, NC
Originally Posted by mike76002
I got the car tuned in Winter so I did not run the car with AC on.
Now in summer, when I turn on AC, the valves're knocking really loud when run under 2200 RPM.
That brings me more attention so I also notice the valves are also knocking w/o AC turned on as well but just not as loud and bad when AC's on.
What might cause it? Bent valves? Bad tune?
My car is MN6 with G5X-2 cam.
Thanks in advance for your help.
-Mike
Now in summer, when I turn on AC, the valves're knocking really loud when run under 2200 RPM.
That brings me more attention so I also notice the valves are also knocking w/o AC turned on as well but just not as loud and bad when AC's on.
What might cause it? Bent valves? Bad tune?
My car is MN6 with G5X-2 cam.
Thanks in advance for your help.
-Mike
Just curious how did you determine it was the valves?
w/ bent valves you would have a loss of power.. because the valves would not seat correctly.. bad tune maybe.. could it be spark knock? or detination brought on by timing being to far advanced perhaps.. thats my guess or thoughts without hearing it for myself or experianceing the problem without doing any diagnosis..
-Rick
Race Director
Joined: Apr 2001
Posts: 19,329
Likes: 16
From: Saint Augustine, FL
Mid-TN Events Coordinator
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16
Originally Posted by VetteTech81
Just curious how did you determine it was the valves?
w/ bent valves you would have a loss of power.. because the valves would not seat correctly.. bad tune maybe.. could it be spark knock? or detination brought on by timing being to far advanced perhaps.. thats my guess or thoughts without hearing it for myself or experianceing the problem without doing any diagnosis..
-Rick
w/ bent valves you would have a loss of power.. because the valves would not seat correctly.. bad tune maybe.. could it be spark knock? or detination brought on by timing being to far advanced perhaps.. thats my guess or thoughts without hearing it for myself or experianceing the problem without doing any diagnosis..
-Rick
It could also be a bad idler pulley, or a bad AC compressor. Get a stethiscope to find out for sure if you haven't already.
Thread Starter
Former Vendor
Joined: Feb 2002
Posts: 7,812
Likes: 3
From: DFW, TX www.vettestripes.com
St. Jude Donor '03-'04-'05-'06-'07-'08
Originally Posted by JR_VETTE
It could also be a bad idler pulley, or a bad AC compressor. Get a stethiscope to find out for sure if you haven't already.Thanks,
-Mike
Burning Brakes
Joined: Jul 2003
Posts: 1,104
Likes: 0
From: "In a van down by the river" CO
Valves don't knock. Rods and pistons knock. It may be detonation or pre-ignition at the stated RPM if under part to full throttle.
If you're sure the valves are the root of the noise, then it's probably just increased valvetrain noise after the cam install.
If it's detonation, take it to your tuner.
If it's the familiar sewing machine noise inside the cabin, and your cam install is correct, then you'll most likely have to live with it. Chris
If you're sure the valves are the root of the noise, then it's probably just increased valvetrain noise after the cam install.
If it's detonation, take it to your tuner.
If it's the familiar sewing machine noise inside the cabin, and your cam install is correct, then you'll most likely have to live with it. Chris
Thread Starter
Former Vendor
Joined: Feb 2002
Posts: 7,812
Likes: 3
From: DFW, TX www.vettestripes.com
St. Jude Donor '03-'04-'05-'06-'07-'08
Originally Posted by lowdowndirty
Valves don't knock. Rods and pistons knock. It may be detonation or pre-ignition at the stated RPM if under part to full throttle.
If you're sure the valves are the root of the noise, then it's probably just increased valvetrain noise after the cam install.
If it's detonation, take it to your tuner.
If it's the familiar sewing machine noise inside the cabin, and your cam install is correct, then you'll most likely have to live with it. Chris
If you're sure the valves are the root of the noise, then it's probably just increased valvetrain noise after the cam install.
If it's detonation, take it to your tuner.
If it's the familiar sewing machine noise inside the cabin, and your cam install is correct, then you'll most likely have to live with it. Chris
But the knocking is a different story.
I will have someone look at it but not the shop that tuned my car
never come back there again
Last edited by Vette Stripes; Jul 17, 2004 at 09:54 AM.
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