The Ford Barn - View Single Post - Piston and cylinder clearance / measurement???

johnneilson · 01-24-2021, 10:39 AM

The Model A engine still has the physics of material thermal expansion.
The original pistons have a "split skirt" this means that the piston has a cut that allows the skirt to compress or expand. This type of piston can survive with the 0.0015 in. clearance.

Modern pistons are made without the relief cut and require more clearance.
There are quite a few variables but, typical clearances are 0.001 to .002 per inch of bore size.

The only advice I can offer is to follow the directions for clearance that the pistons come with.

John

01-24-2021, 10:39 AM	#7
johnneilson Senior Member Join Date: Jun 2010 Location: 34.22 N 118.36 W Posts: 1,054	Re: Piston and cylinder clearance / measurement??? The Model A engine still has the physics of material thermal expansion. The original pistons have a "split skirt" this means that the piston has a cut that allows the skirt to compress or expand. This type of piston can survive with the 0.0015 in. clearance. Modern pistons are made without the relief cut and require more clearance. There are quite a few variables but, typical clearances are 0.001 to .002 per inch of bore size. The only advice I can offer is to follow the directions for clearance that the pistons come with. John __________________ As Carroll Smith wrote; All Failures are Human in Origin.