Mis labeled pistons?

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standup303

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Just finished disassembling my 440. Tops of pistons are all stamped .030 I pulled the measurements below. Are the pistons mis labeled?

Cylinder Piston
#1 4.336” 4.326”
#2 4.329” N/a still installed
#3 4.336” 4.322”
#4 4.333” 4.321”
#5 4.335” 4.321”
#6 4.339” 4.324”
#7 4.335” 4.324”
#8 4.335” 4.322”
 
Well, nothing there, pistons or bores, are .030 over. And they aren't .030 over 426 wedge either.
Ten to fourteen thou piston to wall, you have a MESS there.
 
The BORE is what is .030 over size. The piston has to be smaller for clearance.
 
Where are you measuring the pistons?
Those were at the top before the first ring. I just measured mid piston and they were all 4.345-4.348.

I can only measure about 1/2” down inside the cylinder with the caliper I have and that’s where those measurements are from.
 
Those were at the top before the first ring. I just measured mid piston and they were all 4.345-4.348.

I can only measure about 1/2” down inside the cylinder with the caliper I have and that’s where those measurements are from.
You measure at the skirt.
 
The pistons are pretty close to 4.350. Thinking this caliper doesn’t have long enough arms to get down in the bore for a better measurement.
 
The pistons are pretty close to 4.350. Thinking this caliper doesn’t have long enough arms to get down in the bore for a better measurement.
Calipers are good for quick close measurements.
 
Do you have the new.030 rings? old rings?
You could stick them in the bore in various spots starting from an inch down and measure the end gaps.
It would give you some kind of idea what your working with.
 
Caliper is not accurate enough for this, especially digital or dial calipers. A micrometer is needed & I would doubt once measured properly that there would be 0.003" difference [ assuming no wear.
 
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