Honda D Series Forum banner

1 - 11 of 11 Posts

·
DIY Guru
96 Ranger-stock
Joined
·
637 Posts
Discussion Starter #1
How to Measure, Mic, a Piston

Supertech PN# P4-MA835-N4

Factory supplied spec sheet.



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,


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



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



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


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



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.
Products - supertechperformance.com
 

·
Registered
95 ej2
Joined
·
731 Posts
So here's the grand of all questions you have heard before im sure lol. I have a set of vitaras is it worth it to buy a HF digital vernier caliper to check to make sure they are round? Or dont waste my $8.
 

·
DIY Guru
96 Ranger-stock
Joined
·
637 Posts
Discussion Starter #8
So here's the grand of all questions you have heard before im sure lol. I have a set of vitaras is it worth it to buy a HF digital vernier caliper to check to make sure they are round? Or dont waste my $8.
I would not buy the plastic ones, spend the extra and get the metal ones, they are handy to have around to do quick checks.
 

·
Registered
95 ej2
Joined
·
731 Posts
Ive never seen the plastic ones but you would say the typical metal digital ones are adequate enough?
 

·
Registered
1991 Honda CRX
Joined
·
3,714 Posts
You should also note that each piston manufacturer is unique where they have you measure piston size for P2W. They usually have a measurement to a certain place on the skirt (in this case it's "A" in the diagram). This is very important or else it's all for nothing.
 

·
Registered
Chevy Silverado
Joined
·
1 Posts
To measure the cylinder bore you will need a set of telescoping inside "snap gauges". These are spring loaded machined pieces the expand outward to touch the cylinder Boeing, then are locked at that point. You then measure them with a micrometer to get the inside diameter of the cylinder.
By doing this in 8 places, top of ring travel perpendicular to piston pin ( a ), aligned with pin ( b ), bottom of bore perpendicular ( c ), aligned w/ pin ( d ).
Do some simple math, a-b, c-d tells you if bore is out of round and by how much, a-c and b-d will tell you how much taper ( wear) the bore has.
a - piston diameter determined as outlined in OP will give you piston to cylinder clearance.
 
1 - 11 of 11 Posts
Top