Piston slap

[crackerjack1957]

Something else....................

 

[JS4024]

Just rebuild the motor and quit trying to fix a mechanical problem with snake oil.... Piston slap is NOT normal and will not be cured by changing oils or a filter!

 

[WhiteStar]

You mean this knock at the 2:30 mark?

 

[Simpleman]

You mean this knock at the 2:30 mark?

whats that knock ? Mine is nothing like that

 

[Simpleman]

Just rebuild the motor and quit trying to fix a mechanical problem with snake oil.... Piston slap is NOT normal and will not be cured by changing oils or a filter!

Rebuild the motor ? Its quiet except for the initial start up i couldnt make it do it again if i tried and i dont think redline oil is snake oil it sure helped my tick and never had a tick again

 

[chrisbh17]

Just rebuild the motor and quit trying to fix a mechanical problem with snake oil.... Piston slap is NOT normal and will not be cured by changing oils or a filter!

True piston slap is at least partially a design issue, unless you redesign and rebuild the engine, it won't go away.

Sent from my Pixel 3 XL using Tapatalk

 

[Sherman Bird]

Oil viscosity won't fix piston slap because it is a clearance issue. That was the bad news.... The GOOD news is that piston slap will not affect longevity of your engine. Stop worrying about in and have a great holiday season!

 

[Burla]

Here's the thing, what harm does it do to try different oils and see if it helps? We are talking about an oil change, that's it. 5w30 whatever brand is up to 50% thicker at start up then 20 weight oil, and the numbers are 100 times thicker then operating temps no matter what oil you use. Guys have cured piston slap by going thinner, it is worth a shot so long as you don't leave hemi tick in the wake. If 0w20 redline keeps hemi tick away and keeps piston slap away, why not use it? @2966 is having success with this?

 

[Simpleman]

Oil viscosity won't fix piston slap because it is a clearance issue. That was the bad news.... The GOOD news is that piston slap will not affect longevity of your engine. Stop worrying about in and have a great holiday season!

Thats what burla said so im just gonna leave redline 5w30 in and drive it thanks everybody for the responses

 

[crackerjack1957]

Quote from GM engineer about piston slap:

• Quote:

Are you talking about piston slap during the first few minutes of warmup..??


If so...that is what it is. Nothing to fear or nothing really wrong...just the piston noise until the piston warms up to fill the clearance to the bore.

Pistons rock as they cross TDC where the thrust load from the rod angularity shifts from one side to the other. This makes noise. Harmless, but it is the source of piston slap in most all situations.

To prevent this, pistons are designed with long, tapered, flexible skirts so that they can be fitted very tight in the bores when the bore and piston is cold. The taper of the skirt and flexibility of the skirt then prevents scuffing when the piston is hot. Also, the piston pin in OEM production pistons is always offset to one side....it is NOT in the middle of the piston. By offsetting the pin in the piston, artificial thrust load is created to control the piston "rocking" as it crosses over TDC.

Unfortunately, all of the above control techniques, common in past model engines to the extreme, create excess piston mass, cause friction and cost power and fuel economy. With the desire to build in as much power and free-revving capability and to improve fuel economy as much as possible thru friction reduction these design features are pushed in the other direction on modern engines.

Piston pin offset has been reduced over the years to a bare minimum today to reduce the thrust load generated and reduce friction. Pistons have been lightened up considerably by shortening the skirts. This creates less rotating/reciprocating mass which is good for power, free revving capability and fuel economy. Light weight pistons are great but the skirts, by necessity, are short making it hard to make them both strong and flexible and the shorter skirts make them more prone to rocking.

Unfortunately, when the performance and fuel economy oriented pistons are run cold they are very prone to "slap" until they warm up to operating temperature.

The piston designers and development engineers are always treading the fine line between piston slap cold and friction and power/fuel economy loss when the engine is warm.

It is possible that you are hearing piston noise from an engine that is on the "high limit" for piston clearance so that it makes some noise cold. The good news is that the condition is harmless and that engine is probably a little more powerful (due to less friction) than a "quiet" counterpart. The bad news is that...it makes noise cold.

As an example of what the piston pin offset can do, it was common back in the early 70's to turn the pistons around "backwards" in the large displacement Chrysler engines to gain power. Those engines had large piston pin offsets to create thrust load to control the piston slap. So much thrust load and friction was created that just turning the pistons around in the bores was often good for 10 HP. The engines were very quiet with the pistons in correctly and they slapped like crazy, especially when cold, with the pistons reversed so as to reverse the pin offset.

Racing engines do not have the pin offset and thus the pistons slap like mad...but no one hears them over the open headers...LOL.

The noise is an annoyance but will not hurt anything and the engine is fine.

I don't remember if that engine had full floating pins or not but they can also cause some ticking just after start. Same sort of deal...the "correct" clearances in floating pins will cause clicking after startup for 30 seconds or so. To prevent the start up noise, the floating pin clearance must be kept so tight that the pins are almost press fit again.

 

[OCDTech]

Finally, something i can contribute on, and may have somewhere on the forum before, anyway My Ram has occasional Piston slap, and has quieted some with the Redline 5W-30. (started using for the tick, which it did fix.)

Also where i work we've had many of the fore mentioned chevys 05 to 13 with anywhere from 100,000 to 250,000 miles on them with varying degrees of piston slap and have never had an engine failure. Oh and i have an 01 Subaru Outback with a mild case of it as well 192,000 miles and all is well. Oh wait, Bonus info on the chevys. NEVER a transmission fluid change and weve only had one i can remember ever having to rebuild at 150,000. Mind you these are 2500 series with heavy weight being hauled.

 

[Octane]

About 20 yrs ago some chevys had bad piston slap.GM said finally that the pistons and cylinders were not sized up as before,they would not mic a piston and cylinder and match them together as was common practice before, they would just install them and go.The piston skirts were shortened also.It caused bad piston slap on startup and GM said it would not affect longevity or reliability of those engines.A cop out is what they and FCA are and have been doing for years on quality issues.All in the name of the almighty dollar

 

[Simpleman]

Quote from GM engineer about piston slap:

yes just for a few minutes on start up and after its warmed up the engine is very quiet that is a very good explanation on piston slap thank you very much

 

[2019RamInSC]

Quote from GM engineer about piston slap:

I had a 2000 Camaro SS. With a 5.7 LS1.
It was known for piston slap. Mine did it occasionally. It also ran like a scalded cat. 13.01 in the 1/4 108 mph. With a better driver much better I'm sure.

On the dyno it was 317 hp. Factory rating was 320.

My point? We don't care about piston slap lol. I agree with the above GM guy.

Your mileage may vary.

 

[Burla]

A picture worth 1,000 words, mind you this is two 5w40's (different api rating) versus a 5w30 and a 0w40!

 

[Simpleman]

A picture worth 1,000 words, mind you this is two 5w40's (different api rating) versus a 5w30 and a 0w40!

Very interesting Burla maybe I'll try the redline 0w30 what the hell everyone is trying different weight oil hope your have a happy new year btw i just took out 4 qts of the 5w30 & added 5w20 I'll see what happens

 

[2019RamInSC]

A picture worth 1,000 words, mind you this is two 5w40's (different api rating) versus a 5w30 and a 0w40!

Interesting demo. Kind of predictable result of course.

Now someone go buy four quarts of the same weight oil and do the same test at South Carolina Temperatures. Coldest Month January (47 °F avg). I don't have time I am still mowing the lawn.