How to Measure, Mic, a Piston
 

How to Measure, Mic, a Piston

Supertech PN# P4-MA835-N4

Factory supplied spec sheet.

Attachment 4679

They ask for a bore spec 3.287/83.50 mm, This what is your recommend bore size.


Tools needed for the procedure, Outside micrometers 3-4 inch,
Attachment 4680

But in a pinch, venire calipers will “Get you close” if just doing a quick check

Attachment 4681

A machinist standard is handy to have, so you can zero your measuring tools.

Attachment 4682

The points you want to measure 90* to the wrist pin centerline

Attachment 4683
A view of the appox pot to measure from, with venire caliper.


Attachment 4684
All 4 pistons in the box measured 3.2845

This is going to be Piston to Wall clearance, PTW, in theory. Your actual PTW will vary due to cylinder block finish.

The factory spec sheet says 3.287”/83.50 mm

The formula for converting mm to inches is

Mm x .03937 =Inches

83.50 x .03937 = 3.287395


Now to figure PTW (Theory)

3.287 – 3.2845 = .0025 PTW clearance


I am more accustomed to seeing .0035, but that is on a 85mm piston, and other brands of forged pistons.

That also could be in part due to the “Phosphate dry lubricant”


From the super tech website
SURFACE FINISH:
Finally our "phosphate dry lubricant" coating is applied to protect the rings against "micro welding" and enhance lubrication on the skirt/cylinder area.
Piston Rings are manufactured in Japan with the latest technology for high performance applications.

Quality Control: Performed after every step of the manufacturing process in climate controlled environments to ensure reliability of dimensions.
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