Piston slap, lifter knock, or ?
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
Piston slap, lifter knock, or ?
On a cold start (car sits overnight), about 5-10 seconds after the start there is a very noticeable clacking/knocking sound. This sound will continue for about 10 seconds and then go away completely.
So without actually hearing the sound, what do you think it is? My gut feel is that it's a lifter(s) as the noise doesn't start immediately when started.
It's been doing this for years and it's a little embarrassing when people are around. I don't know when it started.
I do drive it hard and afr is generally on the rich side (10.5). Carbon build up = piston slap?
Btw: car has ALL the bolt ons:
Heads,cam,intake,exhaust,supercharger, etc .
Cam is 228/232 .571/.573 112
With comp cams oem lifters.
So without actually hearing the sound, what do you think it is? My gut feel is that it's a lifter(s) as the noise doesn't start immediately when started.
It's been doing this for years and it's a little embarrassing when people are around. I don't know when it started.
I do drive it hard and afr is generally on the rich side (10.5). Carbon build up = piston slap?
Btw: car has ALL the bolt ons:
Heads,cam,intake,exhaust,supercharger, etc .
Cam is 228/232 .571/.573 112
With comp cams oem lifters.
Last edited by reactor2; May 7, 2015 at 12:36 AM.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
My guess is piston slap. That is pretty common on our cars and matches your symptoms.
I do not think it is lifters since they will clatter right away when you start the car and there is no oil pressure. As soon as there is pressure in a couple seconds, lifter clatter should stop.
$0.02
I do not think it is lifters since they will clatter right away when you start the car and there is no oil pressure. As soon as there is pressure in a couple seconds, lifter clatter should stop.
$0.02
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
My guess is piston slap. That is pretty common on our cars and matches your symptoms.
I do not think it is lifters since they will clatter right away when you start the car and there is no oil pressure. As soon as there is pressure in a couple seconds, lifter clatter should stop.
$0.02
I do not think it is lifters since they will clatter right away when you start the car and there is no oil pressure. As soon as there is pressure in a couple seconds, lifter clatter should stop.
$0.02
I'll see if I can post a video of the noise, although it may be a little hard to hear it over the normal engine noise, supercharger, and the pulley chirp that just showed up this spring (goes away when it warms up too).
I did some reading on piston slap and the cause being carbon build up. I have driven it kinda hard and for a while (learning how to tune) I was running really rich (afr 10-10.5). Now my afr is about 11.2-11.5.
Btw: I have 60k on the engine. I bought it when it had 33k. It's always made some noise on startup.
Last edited by reactor2; May 7, 2015 at 09:29 AM.
Safety Car
Joined: Jan 2014
Posts: 4,496
Likes: 856
From: Walhalla South Carolina
Has anyone tried the LUCAS oil additative, they have one for synthetic and I know from personal experience from using it on jeeps that is quietens the engine knock down which is common for certain jeep models. It is advertised to quieten and boost oil pressure. I just put a qt. in my 93 s10 truck (206,000) miles and it boosted oil pressure. My pressure was OK at speed but at idle it would drop to around 5lb and I would get the check engine light and it has helped and no light now. Directions call for putting in a qt on oil change. my 2$
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
Isn't the piston slap made worse by carbon build up in the piston skirt area? I thought I read that on the GM publication. Not related to oil pressure of course.
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
Has anyone tried the LUCAS oil additative, they have one for synthetic and I know from personal experience from using it on jeeps that is quietens the engine knock down which is common for certain jeep models. It is advertised to quieten and boost oil pressure. I just put a qt. in my 93 s10 truck (206,000) miles and it boosted oil pressure. My pressure was OK at speed but at idle it would drop to around 5lb and I would get the check engine light and it has helped and no light now. Directions call for putting in a qt on oil change. my 2$
I have used them in the past and they did exactly what they said they would do.
Last edited by reactor2; May 7, 2015 at 09:46 AM.
Advanced
Joined: Apr 2015
Posts: 84
Likes: 3
http://www.gmproblems.com/engine.htm
OR
http://ls1tech.com/forums/generation...-engineer.html
AGAIN, it's not an issue and NO magic elixir will fix it.
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Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
You could try one other thing, especially if this just started. Mine did that after a trip I took. Found out it was carbon build-up causing some cold start piston tipping. Ran through some carbon cleaner and haven't had the issue since. I too thought it was piston slap because I had it on a Pontiac I used to have, but once the carbon was removed all is well. I now run Lube Control FP60 in the fuel to help keep out carbon, last time I had the motor open is seems to work pretty well.
You might want to try a Seafoam treatment to see if that eliminates the issue. Not sure if this is your issue, but it might be worth a shot.
You might want to try a Seafoam treatment to see if that eliminates the issue. Not sure if this is your issue, but it might be worth a shot.
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
No.
http://www.gmproblems.com/engine.htm
OR
http://ls1tech.com/forums/generation...-engineer.html
AGAIN, it's not an issue and NO magic elixir will fix it.
http://www.gmproblems.com/engine.htm
OR
http://ls1tech.com/forums/generation...-engineer.html
AGAIN, it's not an issue and NO magic elixir will fix it.
It's not a rod and it's unlikely to be crank journal related as I doubt that noise would go away shortly after start up 10-15 seconds (and not start for at least 10 seconds on start up) and would unlikely take the beatings I dish out.
So we are back to the lifter(s).
Thread Starter
Drifting
Joined: Oct 2006
Posts: 1,724
Likes: 23
From: Minnesota
You could try one other thing, especially if this just started. Mine did that after a trip I took. Found out it was carbon build-up causing some cold start piston tipping. Ran through some carbon cleaner and haven't had the issue since. I too thought it was piston slap because I had it on a Pontiac I used to have, but once the carbon was removed all is well. I now run Lube Control FP60 in the fuel to help keep out carbon, last time I had the motor open is seems to work pretty well.
You might want to try a Seafoam treatment to see if that eliminates the issue. Not sure if this is your issue, but it might be worth a shot.
You might want to try a Seafoam treatment to see if that eliminates the issue. Not sure if this is your issue, but it might be worth a shot.
Advanced
Joined: Apr 2015
Posts: 84
Likes: 3
If piston slap isn't caused, or made worse by, carbon build up then this noise is not piston slap as this amount of noise has not always been present (nobody would buy a car that sounded like this on start up).
It's not a rod and it's unlikely to be crank journal related as I doubt that noise would go away shortly after start up 10-15 seconds (and not start for at least 10 seconds on start up) and would unlikely take the beatings I dish out.
So we are back to the lifter(s).
It's not a rod and it's unlikely to be crank journal related as I doubt that noise would go away shortly after start up 10-15 seconds (and not start for at least 10 seconds on start up) and would unlikely take the beatings I dish out.
So we are back to the lifter(s).
Not necessarily, As the coating on the piston skirts wear over time, the potential for slap increases.