piston to cylinder wall gap

[jan arnett (2)]

What is the required gap between a cast iron piston and the cylinder wall.  The rings are also cast iron for a low RPM engine,  The engine is for a 1923 Moon.

[edinmass]

Bore and stroke please. 

[jan arnett (2)]

On 3/28/2021 at 8:40 PM, edinmass said:

Bore and stroke please. 

Bore 3", stroke 4.5.

 

[Oldtech]

Dykes says .001 for each inch diameter so .003  ( 3 thousandths).  Cast iron pistons can be fairly tight as they don't expand a lot, so .003 would be plenty IMHO. 

[edinmass]

4 minutes ago, Oldtech said:

Dykes says .001 for each inch diameter so .003  ( 3 thousandths).  Cast iron pistons can be fairly tight as they don't expand a lot, so .003 would be plenty IMHO. 

 

I agree........3-4 for cast iron pistons. Modern pistons with modern ring packages and materials may call for something different.

Edited March 31, 2021 by edinmass (see edit history)

[nickelroadster]

Are you trying to reuse the old pistons?  Modern aluminum pistons would probably have just a little more clearance and would probably work  a litle better.

[jan arnett (2)]

I am replacing one piston which had a failed skirt with another original piston.  Thanks for the help.

Jan