Amsoil helped the slap

[tirefryer]

I recently switched from GC 0W30 to the new Amsoil 5W40 (Thanks Pablo)in my LS1 Camaro. The Amsoil almost totally got rid of my cold start up piston slap. It is barely noticable now. However i still get it on warm restarts, but not as long as I did with the GC. Maybe the GC just wasn't thick enough for the loose clearances in my motor. If anyone out there has piston slap in a LS based motor they should give the Amsoil 5W40 a try.

 

[Dick in Falls Church]

Have heard reports that adding an AMSOIL Pre-Oiler will also reduce/eliminate the startup slap. Of course, this is a bit pricier than just changing the oil--especially to correct something that GM says isn't a problem.

 

[Al]

Probably any 40 wt. would have helped.

 

[buster]

I agree with Al

 

[Pablo]

me too

What was the subject?

 

[tirefryer]

A 2002 Camaro Z28

 

[Steve S]

A preluber won't help .

 

[tuong]

i just put 0-30 series 2k, and it is the most difference i felt out of all the oils. i tried everything.
but it helps when i love my car so much i talk to it and she talks back to me. no really i can feel when my car happy or not, with what, and its quieter

 

[tirefryer]

Tuong, what are you running the 0W30 in?

 

[Dick in Falls Church]

>>>A preluber won't help .

Well, Steve, I guess you must know. The one who made the comment was an AMSOIL employee who had been testing the pre-luber--but what does he know?

 

[Steve S]

quote:

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Originally posted by **** in Falls Church:
>>>A preluber won't help .

Well, Steve, I guess you must know. The one who made the comment was an AMSOIL employee who had been testing the pre-luber--but what does he know?

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He knows the product must sell to get his pay check.

 

[vad]

 

[Brett Miller]

A preoiler may not help since the pistons are splash lubed by the rotating crankshaft/connecting rod assembly.

 

[Steve S]

quote:

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Originally posted by Brett Miller:
A preoiler may not help since the pistons are splash lubed by the rotating crankshaft/connecting rod assembly.

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Thanks , Brett I take for granted that people know the basics of how an engine lubes.

 

[Pablo]

Some cars use oil squirters (top/bottom) (not GM, I guess) so a preluber could possibly help start up noises (top/bottom) in those engines.

Never sold a pre-luber, so don't shoot the messenger.

 

[Big John]

I'm not doubting that the original poster's claim of reduced noise,but how does any oil of any weight fill the gap of a piston that is so loose in the cylinder that the skirts touch the wall???I would speculate that it would have to be pretty thick and of a decent flow to quell such a problem,NO?????

 

[tirefryer]

It doesn't have to fill up the gap of the skirts, just the rings. This stops the piston from rocking in the cylinder untill operating temp. are met. Once it reaches operating temps. everything has expanded enough to take up the slack. Mine never slaped once it was warmed up. The fix GM did for this on the LS2 was a floating wrist pin.

 

[tuong]

tirefryer im running it in a honda prelude 01

 

[tirefryer]

OK Tuong I just wanted to make sure in was not an LS1. The LS1 requires a heavier oil than 0W30.

 

[Mike_dup1]

Here is what a GM engineer told me on this subject..

quote:

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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 ckirts 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.

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