Piston Slap | How To Mitigate It And Why It Occurs [HPA Q&A]

How do I mitigate piston slap? Why does it happen?

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[brendenbanks]

Had a block bored out and fitted to 3.5 thousandths clearance per CP pistons specs. The resulting slap ended up polishing the cylinder walls on both thrust surfaces from the pistons rocking in the bores. There was a polished spot on both the top and bottom of the skirt from changeover. These were un-coated pistons. I ended up re-honing (yes the bores opened up to about to 4-4.5 thou) but I sent the pistons out to be coated to take that space back up. They actually came back wider than the bore. I then sanded them down until they fit snug. The engine has been run back in and burns 0 oil. Spark plugs look pristine. I have no idea how long this coating will last (it has been a few hundred miles), but, I learned my lesson. Pay the extra for the coating. It seems to really help alleviate minor thrust issues. These coatings designed to be set up tight and "wear-in" are definitely the way to go. Let the piston self-clearance. you'll get the perfect load distribution across the skirt as high spots wear in.

[PiterStreak]

great stuff! I've learned that sometimes, the block design itself calls for a different tolerance than what even the pistons manufacturer says. my last build has pistons to wall clearance of 3 thou. Once taken apart, the wall has wear marks. This time around I set it at 4.5 thou. the piston moves a little more in the bore but I think it'll be alright.

[robmotown]

here is the best advice ever on piston I rebuilt my vq40 engine ..Nissan navara d40.. forged JE pistons from flatlander racing!!!!the only problem I had is the machining of the block... I.e to big!!!! cylinders were 1 thou bigger than the others!!!! noisy cold start....and even a little noise when at temp!!! change to valvoline xld 10w-40... ... this is a full mineral oil that costs at least half of full synthetic!! Please let everyone know that full mineral oil has a very good dampening effect on piston slap!! .... please try it!!!! It's not a joke!!!.... and this is like for like... as in 10w 40 to 10w TRY IT BEFORE HAVING A SHOT AT

[jaymanilla]

can replacing a piston stop piston slap?
if you rebore the cylinder bore do you need a larger than specification piston to avoid piston slap?
thanks.

[cetGT]

HP Academy: “if you like free stuff”

Me: 😝

[juiceman]

Hey great job as usual..
Can you give a lesson on e85

[goodfodder]

Pretty useless without examples of what piston slap sounds like