LS3 piston slap??
05-05-2014, 08:45 PM
#1
Staging Lane
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LS3 piston slap?? A 416 build with Mahle pistons and .0031 to .0042 piston to bore gap over all 8. Just about 10K miles on the build.
Made noise since the first crank but is a bit worse now.
Vr1 10W-30
two videos.
Cold.... under 100 degrees oil temp.
Hot.... 210 degrees oil temp
Made noise since the first crank but is a bit worse now.
Vr1 10W-30
two videos.
Cold.... under 100 degrees oil temp.
Hot.... 210 degrees oil temp
Last edited by Cruz Lo; 05-05-2014 at 08:54 PM.
05-05-2014, 09:49 PM
#2
It definitely gets more quiet after heating up. Couple of things going on here.
First the piston to bore clearance which is more than double...almost triple of the factory hypereutectic slugs. Forged needs room to expand when hot.
Second aftermarket pistons have centered wrist pins (factory are offset towards the lifter valley). The reason the factory does this is to slightly change the rod angularity @/near directional change for quieter operation.
Thirdly the thin low tension/low friction piston rings are meant to be used with a thinner oil. They can't pull a thicker/heavier oil up the bore when cold starting and the bores get a minimal spraying off the rods at low engine speeds(idle).
Lastly the four inch stroke crank does place a bit more skirt thrust on the walls as the rod to stroke ratio worsens.
The Mahle pistons do have the teflon skirt coating or else it may even be louder.
If you have a quality oil pump I'd try either a 5w or even an 0w synthetic like the Mobil 1 Ow40 and see if it gets a bit better. Probably won't notice a whole bunch different but perhaps some.
First the piston to bore clearance which is more than double...almost triple of the factory hypereutectic slugs. Forged needs room to expand when hot.
Second aftermarket pistons have centered wrist pins (factory are offset towards the lifter valley). The reason the factory does this is to slightly change the rod angularity @/near directional change for quieter operation.
Thirdly the thin low tension/low friction piston rings are meant to be used with a thinner oil. They can't pull a thicker/heavier oil up the bore when cold starting and the bores get a minimal spraying off the rods at low engine speeds(idle).
Lastly the four inch stroke crank does place a bit more skirt thrust on the walls as the rod to stroke ratio worsens.
The Mahle pistons do have the teflon skirt coating or else it may even be louder.
If you have a quality oil pump I'd try either a 5w or even an 0w synthetic like the Mobil 1 Ow40 and see if it gets a bit better. Probably won't notice a whole bunch different but perhaps some.
05-05-2014, 09:59 PM
#3
Staging Lane
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Join Date: Sep 2006
Location: Northern KY
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It definitely gets more quiet after heating up. Couple of things going on here.
First the piston to bore clearance which is more than double...almost triple of the factory hypereutectic slugs. Forged needs room to expand when hot.
Second aftermarket pistons have centered wrist pins (factory are offset towards the lifter valley). The reason the factory does this is to slightly change the rod angularity @/near directional change for quieter operation.
Thirdly the thin low tension/low friction piston rings are meant to be used with a thinner oil. They can't pull a thicker/heavier oil up the bore when cold starting and the bores get a minimal spraying off the rods at low engine speeds(idle).
Lastly the four inch stroke crank does place a bit more skirt thrust on the walls as the rod to stroke ratio worsens.
The Mahle pistons do have the teflon skirt coating or else it may even be louder.
If you have a quality oil pump I'd try either a 5w or even an 0w synthetic like the Mobil 1 Ow40 and see if it gets a bit better. Probably won't notice a whole bunch different but perhaps some.
First the piston to bore clearance which is more than double...almost triple of the factory hypereutectic slugs. Forged needs room to expand when hot.
Second aftermarket pistons have centered wrist pins (factory are offset towards the lifter valley). The reason the factory does this is to slightly change the rod angularity @/near directional change for quieter operation.
Thirdly the thin low tension/low friction piston rings are meant to be used with a thinner oil. They can't pull a thicker/heavier oil up the bore when cold starting and the bores get a minimal spraying off the rods at low engine speeds(idle).
Lastly the four inch stroke crank does place a bit more skirt thrust on the walls as the rod to stroke ratio worsens.
The Mahle pistons do have the teflon skirt coating or else it may even be louder.
If you have a quality oil pump I'd try either a 5w or even an 0w synthetic like the Mobil 1 Ow40 and see if it gets a bit better. Probably won't notice a whole bunch different but perhaps some.
I agree with you and will try a 5W-30 next time I change the oil. It did get a little bit worse this past winter. First winter driving this engine btw... With the knock hanging on longer than before. I drove it with the 10W in the 20's but not much below that.
Motor uses almost no oil at all. I run about a 1/2 quart low due to the lower valley pan.
05-05-2014, 10:39 PM
#4
Thank you. For the 4.070 pistons I have mahle says .0025 to .0035. I followed recomendations and was given a little looser clearance by the machine shop.
I agree with you and will try a 5W-30 next time I change the oil. It did get a little bit worse this past winter. First winter driving this engine btw... With the knock hanging on longer than before. I drove it with the 10W in the 20's but not much below that.
Motor uses almost no oil at all. I run about a 1/2 quart low due to the lower valley pan.
I agree with you and will try a 5W-30 next time I change the oil. It did get a little bit worse this past winter. First winter driving this engine btw... With the knock hanging on longer than before. I drove it with the 10W in the 20's but not much below that.
Motor uses almost no oil at all. I run about a 1/2 quart low due to the lower valley pan.
Sounds healthy; I bet that car scoots real well !!!
05-06-2014, 07:07 AM
#5
Idk why but that PTB clearance sounds huge for 4032 forged pistons. That around 0.004 is 2618 piston territory, you should be able to get well under that with those Mahles. That's the whole point of going with a more brittle piston that expands less.
Basically what you have here is forged piston knock that goes away once they warm up and expand. Just didn't think that was necessary with a 4032 forging. I've heard Mahles in other engines and they are dead quiet at startup, but they were put on with much tighter clearances.
Basically what you have here is forged piston knock that goes away once they warm up and expand. Just didn't think that was necessary with a 4032 forging. I've heard Mahles in other engines and they are dead quiet at startup, but they were put on with much tighter clearances.