Piston Slap Cold????
Thread Starter
Instructor
Joined: Mar 2004
Posts: 125
Likes: 0
From: CONCORD NC
Piston Slap Cold????
just wondering if anybody here has done the recomended gm fix for this and replaced the pistons starting with the biggest piston in the #8 cylinder and so forth????....if so how muh did it end up costing to get it done and did it fix the problem?...thanks 
Melting Slicks
Joined: Nov 2003
Posts: 3,396
Likes: 2
From: North Manchester Indiana
I dont get this at all, what you mean by biggest piston??? there is only one in a cylinder....if you are going to tear into the car to fix the slap issue, you might as well do ALL the pistons......
as for oil filter, it will not help piston slap..
oil filters may help valve train noise.
the best way to stop piston slap is to never let your car cool off, keeping the pistons expanded ...
as for oil filter, it will not help piston slap..
oil filters may help valve train noise.
the best way to stop piston slap is to never let your car cool off, keeping the pistons expanded ...
Melting Slicks
Joined: Feb 2001
Posts: 2,804
Likes: 358
From: Northville, MI
When you start a cold engine, the oil takes some time to get past the oil filter bypass. A few oil filters are made for low pressures to get more oil into the engine at startup. IF you regularly change engine oil, it is the preferred filter. If you change every 7-15000 miles or more then keep the conventional filters.
Another problem is sometimes caused by carbon buildup--use seafoam or top engine cleaner before your next oil change.
Another problem is sometimes caused by carbon buildup--use seafoam or top engine cleaner before your next oil change.
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
Originally Posted by JHALL8569
thats interesting....how does a low oil pressure oil filter stop the piston slap when it's cold? 
Look at it in an extreme sense and I think you'll get the picture: Pretend you replaced all your oil with molasses. This would be akin to starving your engine of free-flowing lubricant, no? A free-flowing oil filter like the K&N speeds the flow through your engine's internals, allowing that slap-preventing film of oil to get to critical areas faster.
Race Director
Joined: Mar 2005
Posts: 10,078
Likes: 17
Originally Posted by Gordy M
When you start a cold engine, the oil takes some time to get past the oil filter bypass. A few oil filters are made for low pressures to get more oil into the engine at startup. IF you regularly change engine oil, it is the preferred filter. If you change every 7-15000 miles or more then keep the conventional filters.
Another problem is sometimes caused by carbon buildup--use seafoam or top engine cleaner before your next oil change.
Another problem is sometimes caused by carbon buildup--use seafoam or top engine cleaner before your next oil change.
I'll let you get 'im on this post EB....
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Melting Slicks
Joined: Nov 2001
Posts: 3,088
Likes: 1
From: NC
Originally Posted by wrustywrench
as for oil filter, it will not help piston slap..
oil filters may help valve train noise.
oil filters may help valve train noise.
Oil viscosity has nothing to do with the inherent C5/LS1 piston slap.
The main culprit is expansion as stated as the piston skirt is
actually making some contact with the cylinder wall until it
expands enough to keep from rocking.
Unless a motor hasn't run for quite a while, there is always some
amount of residual lubricant on the cylinder walls and unless the
oil is the consistency of molassis (which it isn't), then it flows very
quickly. Certainly more quickly than the 5 - 7 minutes or so needed to
heat up and expand the pistons.
Even so, this noise would be vlave train noise and not piston slap.
As far as carbon deposits go, two things happen that can sound like
piston slap. Enough carbon can build up on the piston top/valves to either imbalance the piston enough to rock abnormally and/or make contact with the valves which sounds like a longer term slap noise.
There will most likely be some pinging involved with this situation.
The culprit here is the infamous oil ring which needed to be redesigned
and replaced for the late 2000 and 2001 model years.
GM supposedly fixed the slap situation by changing the skirt length and
by using a polymer coating to reduce the slap noise.
...George
Race Director
Joined: Dec 2000
Posts: 19,304
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From: San Diego CA
I have to go by actual experience when I tell others that using a high-flow (low pressure drop) oil filter tames the cold-start tapping. Installing a K&N oil filter significantly reduced this tapping (oil viscosity range was not changed) in my LS1. In fact a neighbor had a very similar tapping noise which was eliminated after he installed a K&N oil filter and changed oil viscosity from 20W-50 to 10W-30. I can't say that I know exactly why - I can only surmise, but I do know that more low flow=more noise.