95ONE

iTrader: (1)

I've seen people ask this question a lot in the fly cutting threads. Since I beat up my piston by accident while trying to fly cut them on the mill. Today I figured no harm in cutting it up to learn something. LS6 piston.. 2003.

this is showcasing the intake side. Most people will be cutting deepest here, or just this side. Also looking at the exhaust side, the relief is so close to the outside, that 90% of the fly cut stays well within the seriously thick part of the piston. Its the Intake side that gets near the thin stuff. The good news is, its only in a small spot where the fly cut is the deepest and the piston is the thinnest. Otherwise it's really thick on the outside of the fly cut, and the Fly cut thins out (angles up and out) where it reaches the thinnest part near the center. I cut .1 into this one. Aw crap. i forgot to measure the pistons total thickness without the flycut. I can do that tomorrow. Well, actually, some kindergarten math will tell you from the pics with the dial caliper, they are about .275-.29" thick at their thinnest spot. (Casting irregularities at play here. Check out the 5th pick down and compare the two thin spots. Not consistent, and I'm not mistaking the offset pin position/casting with that) So it seems like .100 is pretty safe. (by my own personal guidelines that is.)

I'll just post up most the pics so you can figure out what you're comfortable with if you want to fly cut yourself.

it seems there's a truckload of thickness on the farthest outer sides of the cuts. Gets thinner and thinner as you near the far side of the fly cut "crest" then gets thicker again as the cut backs out of the piston. So there's really only a very small area that even begins to get thin. I would even push it .125 if I had to. Glad I don't, but I would.

Here are the pics.

This was the first cut I made. You can see how damn thick they are on the outsides. (holds pin)





I looked underneath and had an Idea where the thinnest spot would be and I cut it there for illustration. (horizontal band saw make nice straight cuts)




And here are the rest with cheap caliper pics (digital read out easier for pics)

3rdCoastPowerSports

iTrader: (5)

cool pics... im curious as to the answer

95ONE

iTrader: (1)

I guess I never really gave a definitive one. You'll find I do not like to say "can't" Too many people have said that to me and saw a bunch of "can". Or it just ends up in pointless arguing.

But I think what I did here. .1" deep is about it. It is all a personal preference. So I didn't really give a number because it's between you and what you're comfortable with. I can see someone going .12" deep on an N/A build. I personally wouldn't want to. But, this should give you a very clear idea how thick the piston actually is in its' thinnest part to guide your decision on how deep you are willing to risk it.

chrisfrost

iTrader: (8)

My opinion is that the flycut piston is plenty strong to take at least 450-500rwhp but where I see any possible problems not necessarily with that depth a flycut but heat build up can melt a thin part of a piston . But like I said I don't think that cut would cause any problems to a point anyway .

JPH

iTrader: (2)

Depth I would not cut any deeper then .110 myself(.125 max), but radial clearance is always the other problem with big valves and milled heads.