rod knock quiet down when engine warms up?-video added - Chevelle Tech
Chevelle Tech join team chevelle as a supporting member  
Chevelle Parts at SS396.com      
GROUND UP & SS396.com         
Official Sponsor of Team Chevelle
     

Auto Insurance

Chevelles.com is the premier Chevrolet Chevelle Forum on the internet. Registered Users do not see the above ads.
Performance Our High Performance area

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old Mar 22nd, 11, 10:52 AM
greg_moreira greg_moreira is offline
Senior Tech Team
 
Join Date: Nov 2004
Location: Pittsburgh Pa
Posts: 2,111
Default rod knock quiet down when engine warms up?-video added

Hi Guys.

Just curious....Id think not, but will a rod knock quiet down when the engine warms up?

Earlier this winter I started the car and had some noise that resembled either lifter noise, or a rod knock. When I blip the throttle and the revs settle back down its more prononced for a brief second or two.

I was trying to find the location of the knock and I found(makeshift stethascope) that its the loudest on the trans bell on the passenger side. I though it was a converter bolt, but found nothing wrong there.

I started thinking rod knock, and I tried to investigate this past weekend. Once the water temp hits around 140 or so...the noise is entirely gone. I kind of ruled out lifter/rocker noise because I can barely hear it through the valve cover, so Im back to trans, piston noise, or rod noise(but based on the location of the noise...trans or rod "seemed" mostly likely). Would you expect rod noise to go away with heat?

I added a vid. Its only in the 40's right now, so prime time for noise. Number one..its waaay louder in the vid that real life. Number two, notice when I bring the rpm's up around 2 grand, it completely goes away. And after it warms up...its silent as well. Sorry there isnt much of a visual. This was taken down under the car by the passenger side collector(thats where its loudest).


Last edited by greg_moreira; Mar 22nd, 11 at 8:44 PM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old Mar 22nd, 11, 10:56 AM
Busted Knuckles Busted Knuckles is online now
Senior Tech Team
 
Join Date: Dec 1998
Location: Lubbock, TX
Posts: 3,460
Default Re: rod knock quiet down when engine warms up?

No, I'd think it would get worse as the oil warms up and thins out.
Sounds like piston slap, but I'm curious about what the experts say...
__________________
Gary Adrian
FCS Harmony Racing

'Cause if they catch you in the back seat trying to pick her locks,
They're gonna send you back to mother in a cardboard box...
You better run!
Reply With Quote Quick reply to this message
  #3  
Old Mar 22nd, 11, 11:03 AM
camaroman7d camaroman7d is offline
Senior Tech Team
Royce
 
Join Date: Dec 2003
Location: Vacaville, California
Posts: 1,794
Default Re: rod knock quiet down when engine warms up?

Don't overlook your harmonic damper. Could very well be loos and once heat gets into the crank it tightens up a bit. This would also transmit the sound to the area you were hearing it. Just some else to look into before getting to serious.
__________________
Royce (NO XQSSS) Bradley
www.facebook.com/driveyourjunk
Short Video w/sound Blown SBC 1961 Skylark, Borla mufflers and 3 1/2" exhaust.
http://www.youtube.com/watch?v=DSLsGgDjFXE
Reply With Quote Quick reply to this message
  #4  
Old Mar 22nd, 11, 11:07 AM
cuisinartvette cuisinartvette is offline
Senior Tech Team
Sheepster. BAH!
 
Join Date: May 2006
Location: San Fernando Valley, Ca.
Posts: 8,744
Default Re: rod knock quiet down when engine warms up?

Flexplates are known to crack around the bolt holes, could be hearing that.
__________________
Quote:
This post is a duplicate of a post that you have posted in the last five minutes.
Reply With Quote Quick reply to this message
  #5  
Old Mar 22nd, 11, 11:08 AM
jmartorana jmartorana is offline
Tech Team
 
Join Date: Sep 2008
Location: Long Island NY
Posts: 315
Default Re: rod knock quiet down when engine warms up?

Could it be a wrist pin?
__________________
1969 Nova SS
502 CID
Pro Systems
cstraub big squishy roller
AutoGear M23W
4:10
Reply With Quote Quick reply to this message
  #6  
Old Mar 22nd, 11, 11:25 AM
67chevelle406 67chevelle406 is offline
Tech Team
kevin
 
Join Date: Dec 2008
Location: cincinnati
Posts: 656
Default Re: rod knock quiet down when engine warms up?

I was thinking wrist pin I had one that made noise when cold but quit when it was warm. I also had a skirt broke off a piston once that done the same thing. Is the noise slow or fast usually valve train noise is faster paced.
__________________
67 chevelle 406 10-1 200cc dart iron heads lunati hyd flatt tappet 480 230 cam perf rpm 750 holley vac sec. 3200 edge stall 3.73 gears 12.23@109 1.74 60ft ***SOLD***

1968 Camaro in progress stock 5.3 with a 75mm turbo for the wifes driver.

1972 Nova 427 BBC ,TH400,3500 stall,9"rear 3.55s track times soon to come.
Reply With Quote Quick reply to this message
  #7  
Old Mar 22nd, 11, 11:32 AM
crazydavey crazydavey is offline
Lifetime Premium Member
Davey
 
Join Date: Feb 2010
Location: Lafayette, Or.
Posts: 6,655
Default Re: rod knock quiet down when engine warms up?

what kind of pistons do you have Greg? A forged piston with clearances on the fat side will typically slap (knock) when cold....if the noise goes away when it heats up expansion is "fixing" the noise so look at things that expand...Dave
__________________
Chevelle
http://www.firstgenmc.com/photopost/...um/david_4.jpg

SloMo...
https://www.youtube.com/watch?v=Fa13syTsA0E

'67 Chevelle 509 hyd roller
3.89's
9.44 best mph 141.30
5.97 best mph 114.44
3520 lbs
Straub/Foxwell
prepared by:
Nassimbene
&
Trubey

E-Store at
crazydaveyracing.com


Davey..
TC Gold Level Know it All
Reply With Quote Quick reply to this message
  #8  
Old Mar 22nd, 11, 12:02 PM
greg_moreira greg_moreira is offline
Senior Tech Team
 
Join Date: Nov 2004
Location: Pittsburgh Pa
Posts: 2,111
Default Re: rod knock quiet down when engine warms up?

It is a pretty fast paced noise. reminded me of valvetrain noise...but the origin is whats throwing me(not being able to hear thru the valve covers).

I thought piston slap, and they are forged. If thats the case though...its only one piston, and it never happened once in warm summer weather. Just in the 50ish degree weather of now.

Maybe the 30 degree outside air temp difference literally is enough to keep these pistons "tight" in the summer, but let them loose enough to be noisy this time of year?

As you can tell....Im tryin to talk this issue out of being a problem with the bottom end, and I hope its listening! First things first is I suppose just gotta look closer at the flexplate, and if I have to...yank the trans and get the whole trans/converter out of the mix and see what the noise does.

best case scenario would actually be flexplate, or valvetrain. Its still got the flat tappet in it, but Ive got a whole new roller valvetrain going in. Rockers are on backorder, so I cant start yet...but yeah, everything must go. Problem solved. I guess a little piston slap when cold isnt the end of the world either as long as clearance isnt ridiculous.
Reply With Quote Quick reply to this message
  #9  
Old Mar 22nd, 11, 12:06 PM
67chevelle406 67chevelle406 is offline
Tech Team
kevin
 
Join Date: Dec 2008
Location: cincinnati
Posts: 656
Default Re: rod knock quiet down when engine warms up?

Don't know your setup but I have heard fuel pump rods make noise to.
__________________
67 chevelle 406 10-1 200cc dart iron heads lunati hyd flatt tappet 480 230 cam perf rpm 750 holley vac sec. 3200 edge stall 3.73 gears 12.23@109 1.74 60ft ***SOLD***

1968 Camaro in progress stock 5.3 with a 75mm turbo for the wifes driver.

1972 Nova 427 BBC ,TH400,3500 stall,9"rear 3.55s track times soon to come.
Reply With Quote Quick reply to this message
  #10  
Old Mar 22nd, 11, 12:22 PM
stroud6 stroud6 is offline
Tech Team
mark
 
Join Date: Jul 2009
Location: polk county mo
Posts: 147
Default Re: rod knock quiet down when engine warms up?

from your description and forged pistons I agree with piston slap. mark
Reply With Quote Quick reply to this message
  #11  
Old Mar 22nd, 11, 1:23 PM
grovey grovey is offline
Senior Tech Team
Tim
 
Join Date: Jul 2005
Location: pa
Posts: 1,363
Default Re: rod knock quiet down when engine warms up?

my guess is main bearings.
Reply With Quote Quick reply to this message
  #12  
Old Mar 22nd, 11, 2:10 PM
bracketchev1221 bracketchev1221 is offline
Senior Tech Team
 
Join Date: Dec 2005
Location: Lancaster, PA
Posts: 9,086
Default Re: rod knock quiet down when engine warms up?

My "guess" is Piston Slap. I just took apart my 350 that was REALLY loud when cold and noisy when warm. Could never tell exactly where the noise was from. But when I took it apart, I could move the pistons side to side in the bores. These were Hypereutectic pistons as well so they should have been tight. The short was reassembled with forged pistons and it visibly has less clearance than it did then.
__________________
Ray

http://s30.photobucket.com/albums/c3...t=DSC01615.jpg
Best pass so far 9.039 at 148.10, 1.266 60'
Reply With Quote Quick reply to this message
  #13  
Old Mar 22nd, 11, 5:45 PM
Camaro_fever68 Camaro_fever68 is offline
Senior Tech Team
Ray
 
Join Date: Nov 2005
Location: Baton Rouge, La
Posts: 2,039
Default Re: rod knock quiet down when engine warms up?

I say piston slap. I have an older engine that has severe piston slap in cold weather that lasts for about a minute. Once it warms up, it's completely quiet.
__________________
Ray
Reply With Quote Quick reply to this message
  #14  
Old Mar 22nd, 11, 6:19 PM
matt's66 matt's66 is offline
Senior Tech Team
Matt
 
Join Date: Jun 2009
Location: CT
Posts: 1,260
Default Re: rod knock quiet down when engine warms up?

An old timer once told me that if it gets louder as the engine warms up, it's bad. If it gets quieter as it warms up, no worries. I'm going with piston slap or wrist pin/s. My tired ol' 396 has an ever so slight cold knock when the ambient temp is below 45 degrees and only for a min. During the summer it's quiet as a church mouse. But, if you're gonna tear into it anyway for upgrades, might as well rule out the balancer and flexplate just for peace of mind.
__________________
1966 Chevy Caprice 2 door sport coupe
396 325 h.p. 95% original, matching #'s
Th400, 2:73 12 bolt
Original dealer invoice, title from orig. owner, Protecto-plate
Mods:
Dual flowmasters
Edelbrock 1406 600 cfm carb
Pertronix points eliminator
Adjustable vac can and re-curve
Open element aircleaner with 3" K&N
2000 rpm stall
Trans-Go shift kit
Reply With Quote Quick reply to this message
  #15  
Old Mar 22nd, 11, 7:44 PM
BillyGman BillyGman is offline
Lifetime Premium Member
 
Join Date: Oct 2005
Location: CT,USA
Posts: 11,345
Default Re: rod knock quiet down when engine warms up?

Quote:
Originally Posted by greg_moreira View Post
Hi Guys.

Just curious....Id think not, but will a rod knock quiet down when the engine warms up?

Earlier this winter I started the car and had some noise that resembled either lifter noise, or a rod knock. When I blip the throttle and the revs settle back down its more prononced for a brief second or two.

I was trying to find the location of the knock and I found(makeshift stethascope) that its the loudest on the trans bell on the passenger side. I though it was a converter bolt, but found nothing wrong there.

I started thinking rod knock, and I tried to investigate this past weekend. Once the water temp hits around 140 or so...the noise is entirely gone. I kind of ruled out lifter/rocker noise because I can barely hear it through the valve cover, so Im back to trans, piston noise, or rod noise(but based on the location of the noise...trans or rod "seemed" mostly likely). Would you expect rod noise to go away with heat?
Greg, I've had a rod knock in one of my previous cars, so I've been through that before. There's a very simply and sure way to find out for certain whether it's a rod knock or not:

Get a pair of rubber gloves, and/or a pair of sparkplug boot pliers or atleast regular pliers with rubber coated handles. Start the engine up, and while it's running and making the knocking noise,(in your case, when it's stone cold) pull one of the sparkplug boots off to see if the knocking noise stops. If it does, then push the boot back onto the plug while the engine is still running, and the noise will immediately return as soon as you do (if it's a rod knock in that corresponding cylinder). If that doesn't eliminate the knock, then go to the next boot, and pull that one off and put it back on again with the engine running. Do this with all 8 of the boots one at a time. If it's a rod knock, you will immediately hear the difference by ear beyond any shaddow of doubt just as soon as you tug off the boot, and the noise will immediately return the second you push the boot back onto it's spark plug.

If you go through all 8 boots, and it doesn't change the knocking noise, then it isn't a rod bearing that's knocking, and you've ruled out that possibility. this is a simple and effective diagnosis procedure. If it's anything in the valvetrain, the noice will not stop regardless of which sparkplug boot(s) you remove.
__________________
70 Chevelle SS clone (632 CI powered).
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply
Chevelle Tech > General Tech Area > Performance      Current Topic: rod knock quiet down when engine warms up?-video added
Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 12:12 AM.


Is there a site like this for?    El Caminos Camaros Novas Impalas GTO Chevy Punch All Chevys

2009 Team Chevelle - AutoForums