My previous 2000 5.3L Silverado had piston knock when it hit 120,000K.
It lasted for about 30 secs as well. It wasn't a slight tick, it actually knocked really loud! It only did this on cold mornings and only when the engine was under load. After 30 secs it went away. Though it sounded like the piston rod was loose. You could even feel the knock. Is this the same thing you guys are talking about?

Jim

I am refereing to a slight piston slap after the engine is warmed up.

When you say slap, I'm assuming you mean like a tick or slight tapping noise.
That was always an issue with LS1 truck engines. I don't think it really hurts anything from what I've read about it.
Though mine began a harsh knocking noise on cold start-ups at high mileage (120,000).
Didn't sound good. It did it for a whole year without failure, so I traded it at 145,000 miles.
I have no idea what it was. Anyone with a possibility of what it was?

Jim

thicker oil is most likely just reducing the noise- not the actual slap. Dont do that, use the oil your engine calls for.

That's just covering up the problem.

Jim

Well the way I see it, here are the options

1. Run 10w30 to reduce the slap

2. Get a remote starter and make sure the engine is warm before you get in

3. Bore the block and fit oversized pistons to tighter tolerances. (expensive, but its the only way to permanently fix the problem)

1. that doesn't fix it- it just makes it so you cant hear it. Now you are running the wrong oil and should expect other problems to result (or problems to occur prematurely)

2. Yeah, always good. You should really wait at least 30 seconds before driving it around. Just start it, hop in. Steat belt, find a radio station and count to 10 or something when its cold. Just take it really easy on the throttle for the first few minutes. Your oil is cold and thick.

3. Talk about reinventing the wheel and splitting the atom.

10w30 wont hurt anything. im willing to bet 80-90% the guys here use 10 weight instead of 5

Up until about 1 year ago I worked for an automotive repair chain for over 17 years. We used various fuel system cleaning products at different points over the years. We would always test for tailpipe emission improvements before we switched brands. There is alot of snake-oil out there. The best IV bottle induced products that go in thru a vacuum line will be ones that have an extremely high flash point, in other words if you pour a small amount in a bottle cap you won't be able to get it to burn with say a cigarette lighter. The ones that will flash easily will not make it into the cylinder before they are gone there-by eliminating the top of the piston & combustion chamber cleaning that is needed to reduce carbon buildup. On many vehicles the tolerance between the tallest part (usually the edge) of the piston and the bottom of the head is so tight that a few thousandths carbon buildup will cause a knock that many confuse with piston slap. A good IV intake induced cleaner such as Berryman or Run Rite will help lessen the carbon problem. It should be done about every 15 to 24K. The engine needs to be run at between 1500 & 2000 rpm on a V8 whilel the service is in progress to prevent puddling in the intake, this is with a slow drip IV bottle designed for the product used.

thank yu, thats what I have been trying to say.