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The piston skirt is never the same shape as the bore, leading to higher contact pressure and thus greater wear at specific areas of the skirt, typically a vertical band right down the center. The coating is applied to make clearance deliberately tight, then wears away to the point that contact pressure is even across the entire skirt. Once that condition is achieved, the contact pressure, even on the major thrust side of the piston, is so low that the coating stops wearing and the piston is a perfect fit. So the coating fits the piston perfectly and eliminates skirt wear. I'm not sure if it affects bore wear significantly, as a high performance engine is probably getting more bore wear from the rings than from the skirts, but lower contact pressure is easier on the skirts as well.

You could be their spokesperson

yes to all that, but I'm not sure when it starts to actually matter is all I meant. For sure it stops rattling pistons that are fit loose in the bore which is what I'm after, any other benefit would be gravy.

I'm re-doing my honing setup before continuing. I ordered a chunk of aluminum and will use it to make a holder that matches the block so the cylinder is fully supported. Then that will get mounted on the coolant pump/tank setup from the my saw that that I haven't used in years to keep the stones are clean as possible and everything as cool as possible and maybe add a bucket as a spray guard to keep me and the shop floor as clean as possible. I'll be back to honing in a couple days.

Still working on the honing fixture but look what showed up today, Tach stickers!  and they look really good, seem to fit right, they sent 2 full sets plus extras of the white and more extras of the tiny white stuff.  

The stickers are cool. Glad the hone arrived in time for some weekend honing.
There are several different grit of stones. Start with a medium and see how the sleeve feels. You will feel the out of round and or taper. If you have taper, just dwell a bit and then make a pass or two and check the feel. This can be done while you are working on out of round as well. I usually try and get the taper fixed first,then work the out of round. Once I am happy, measure it and see what you need to do to hit the target number.
You can make a bottom stop on your fixture. The hone has a flat bottom circle that can touch and go.

_________________
Wade Williams
Master Ferrari Tech
Restoration Tech
Engine Machinist
Fabricator
Racecar Driver

Thanks Wade!

Spent basically all day making a way to complicated honing fixture....honing will resume tomorrow.

Turned on the pump this morning and spray oil everywhere....added a bucket but there wasn't any good way to handle the bottom so it dribbled all over the floor....eventually put the whole setup inside a bin. Oil contained.

I started with a scrap cylinder and spent all morning chasing out of round before realizing it was the clamping nuts on the fixture, hand tight is fine, touching it with a wrench is not! That means there is a delicate balance off holding the cylinder vs spinning the cylinder with the hone, but second attempted cylinder is within about .0005 total runout right now and looking pretty good. This was the one that needed to most metal removed so small mistakes wouldn't matter and right now it needs about another 1.5 thou to get to where the others will likely clean up.

I'm not going to post a pic of me quickly removing out of round with a drum sander because doing anything like that would be wrong and likely incur Wade's wrath so shhhhhhh.......but I hear you can remove 2-3 thou of out of round from 1 end of a cylinder in less than a minute that way

Now I am just an armchair commenter but wouldn’t you want to do this in the block with a torque plate installed? Was this what the shop was supposed to do?

Hey hey, let's not muddy the waters with details. He is getting the cylinders honed (or drum sanded ). They will be great.

(yes, in the block, torque plated would be best, but we are not telling Mark that now. )

Shhhhhh.

_________________
Wade Williams
Master Ferrari Tech
Restoration Tech
Engine Machinist
Fabricator
Racecar Driver

Because that would be complicated, time consuming and awkward...