383 Engine knock?
Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
Likes: 7
From: Ft Wayne IN
383 Engine knock?
My new 383 with about 500 miles on the motor started making a slight knocking sound under the front of the motor. I don't get it until the motor is warm and is only noticable at idle. Are stroked motors with forged pistons known for any piston slap? I have plenty of rod and piston clearance on the block. Also it only seams to be coming from the very front and also seems to be coming from the bottom of the motor. Any thoughts? I just got this thing running good to, this is realy got me worried
Team Owner
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From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
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Tell us about the timing chain
If you installed the double roller, did you installed the new water pump gear set?
If you installed the double roller, did you installed the new water pump gear set?
Safety Car
Joined: Apr 2011
Posts: 3,660
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My new 383 with about 500 miles on the motor started making a slight knocking sound under the front of the motor. I don't get it until the motor is warm and is only noticable at idle. Are stroked motors with forged pistons known for any piston slap? I have plenty of rod and piston clearance on the block. Also it only seams to be coming from the very front and also seems to be coming from the bottom of the motor. Any thoughts? I just got this thing running good to, this is realy got me worried
Mine also has a noise thats not a knock, more like a rubbing or bumping that comes and goes...in the bottom, except toward the rear. Can;t hear it under the hood, mostly in the cabin at idle. Gone the next day, and cannot pin it down.
My thoughts are crank run-out. I can;t prove it without pulling it apart, but thats the only thing that makes any sense...the crank floating back & forth in the bearings and main seals . Its so mild and intermittent that its hard to justify deeper examination.
Is this possible with your new build? Crank run-out gets overlooked sometimes.
Last edited by leesvet; Apr 29, 2011 at 06:59 PM.
Race Director
Joined: Apr 2003
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From: moraga ca
Piston slap usually happends when the motor is cold and the piston to cylinder wall clearance is at it's greatest. Knocking when warm can be bearing noise when oil viscosity decreases. Stroker motors shouldn't be any noisier than standard stroke motors unless the block wasn't clearanced and the rods are contacting the block or if there is an internal mechanical problem.
Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
Likes: 7
From: Ft Wayne IN
Yes I have a double row that had lots of clearance issues but I couldn't feel any issues when turning it over by hand after I and cleaned up the bad spots. I have a 92 block with upgraded distributor and an electric water pump. If it was a bad bearing wouldn't it do it all the time i.e. when cold?
Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
Likes: 7
From: Ft Wayne IN
Yes I have a double row that had lots of clearance issues but I couldn't feel any issues when turning it over by hand after I and cleaned up the bad spots. I have a 92 block with upgraded distributor and an electric water pump. If it was a bad bearing wouldn't it do it all the time i.e. when cold?
Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
Likes: 7
From: Ft Wayne IN
Ok I just did the old wooden dowl rod as a listening device and it's definately coming from the bottom of the chain case cover and within. I hope it's only a timming chain clearance issue, the only problem is I would think if the chain was hitting it would be a more continues noise wouldn't it? This noise has the timming of the crank revolution "if that makes sense".
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
Use the search, there are plenty of threads on how to shave the timing chain cover using a carbide bit.
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Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
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From: Ft Wayne IN
If bearing clearances were good on install what would be causing this? I have great oil pressure but I noticed at idle there doesn't seem to be any oil laying in the heads or valve covers until the rpm's are brought up?
Would the metal in the filter have a certain look compared to metal from the timming chain rubbing or somthing?
Would the metal in the filter have a certain look compared to metal from the timming chain rubbing or somthing?
Last edited by C4vettrn; Apr 30, 2011 at 01:26 PM. Reason: add
Thread Starter
Burning Brakes
Joined: May 2009
Posts: 1,014
Likes: 7
From: Ft Wayne IN
Ok I changed the oil and opened the old filter. What is the telltale sign of a bearing failure? I don't see anything gleaming, there are some small slivers that seem almost like aluminum other than they are whitish in colore and don't seem magnetic either, could this be a coating on the bearing?
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
my left catalytic converter brick fell apart when I high centered, The brick pieces are in the muffler, and it sounds like a diesel. Only inside. outside, it sounds like a little guy with a precisely timed hammer.
BTW, the right brick bounced around enough that it was like sand. The cat housing was empty. nothing but the air pipe.
I just had bullet cats put on it Wed.
and it's a 383 that sounds like there's noise coming from just under the plenum.
Been there since I first fired it up on the run stand, and I took the entire intake off, and checked everything out, but couldn't find anything.
BTW, the right brick bounced around enough that it was like sand. The cat housing was empty. nothing but the air pipe.
I just had bullet cats put on it Wed.
and it's a 383 that sounds like there's noise coming from just under the plenum.
Been there since I first fired it up on the run stand, and I took the entire intake off, and checked everything out, but couldn't find anything.
