RT2SJB

my 07 z51 has been diagonsed with piston slap. Has anyone reduced the noise this condition causees by changing the viscosity/type of oil? I am in south Texas in extreme heat.

R&L's C6

If it is truly piston slap I don't see how the viscosity of any oil could help.
The theory behind piston slap is the bore is to large until the piston heats up and expands. I don't know how any oil could play a part in fixing that.

N8sFavToy

My truck does it anytime it's below 40 degrees. I wondered the same thing, but didnt think it would help.

RED HUSKY

Its GM's engine design. They claim it does't hurt the engine in any way but it's hard to belive that.

Gman in NC

My Jeep Wrangler is the same way. They've always claimed to have piston slap on the I6. Mine has been doing it for 111,000 miles now. No problems. Haven't noticed it in the Vette though.

Gearhead Jim

Our 2001 had noticable piston slap when cold, but neither our 2006 nor our current 2009 have any that I can hear. Usually, it's harmless.

RT2SJB

harmless yes it goes away after it reaches *160. Just wondering if anyone has been able to reduce the noise. The dealer told me not to worry about it, it runs fine.

Mike's LS3

Piston slap can develop from excess carbon build up on the piston ring-lands. I experienced piston slap at cold start up and it was less audible as the engine warmed up. I performed two treatments of BG44K power enhancement, one treatment per 12 gallons of gas. After the first treatment about 80% of the noise was gone and 100% after the second. If you have piston slap from loose tolerances, BG44K will not help.

BTW: I had about 23k miles when I first developed the piston slap at cold start up. The GM tech verified the noise as piston slap and said they could do nothing. At the time, I had an aftermarket air intake with the stock tune. I am speculating, the aftermarket air intake with the stock tune caused an overly rich condition in the power enrichment mode. This rich condition over time caused excess carbon build up on my piston ring-lands. Since then, I installed my oem LS3 air intake, preformed two treatments of BG44k, changed my spark plugs and oil. My car runs great and no more piston slap.

RT2SJB

I did one treatment of 44k and it seemed to help. It turned the oil black so I had it changed today. Will the second treatment damage the oil? Since it made some of the noise go away i am considering another treatment. This week-end i took it on a long 200 mile trip and thought that would clear out any remaining carben, but the trip made no difference. The knock only lasts for about two minutes and its gone.

Mike's LS3

Wow, oil turned black probably due to the carbon burning off the pistons and ring-lands. I would do another treatment of BG44K and see if there is further improvement. If the oil turns black again, as a precaution, I would change it. You want to eliminate any chance of oil contamination. Do you have any mods on your car? Is your car running rich?

RT2SJB

Yes i have about the same air intake as the post above and the exhaust tips seem to be black. I will try another treatment and i agree that should fix it. To me the sound is similar to a injector knock on a diesel engine if you have ever heard that.

Raazor