Piston Ring Clearance
 

I am rebuilding an engine with a set of NORS pistons and notice that the ring grooves were not as deep as the previous set. These are 0.0175 inches deep on the top two grooves and most of the pistons I have around here are 0.195 to 0.210 inches deep. I have also notices some variation in the cross section thickness of the various rings, everything from 0.175 down to 0.155 inches thick, some with 0.020 thick expanders behind a 0.140 thick oil control ring. All of these were designed for the 28-34 A/B engines.

Any thoughts about how much of a gap there should be between the inner surface of the ring and the inner radius of the groove? Thanks much.

Re: Piston Ring Clearance
 

A general rule of thumb is .002" for each inch of bore size. As to the depth of the piston grooves, as long as you can completely close your ring compressor on the piston with rings installed, you know the grooves are deep enough.

Re: Piston Ring Clearance
 

Just so long as the ring will go flush with the side of the piston, when in the groove,
it can't stand out of the groove.

Russ...004 per inch of bore, unless it's a hyerutectic (SP)

Dudley

Re: Piston Ring Clearance
 

Flip the ring over and put it in the groove it will be flush or lower you won't have deep groove ring in a shallow groove piston in that application.The measurement you are taking on the ring is referred to as radial wall thickness. Where you can have trouble is a deep groove ring in a shallow groove piston but that is not your application. Yours is not available with a shallow groove piston. Only late model stuff.

Re: Piston Ring Clearance
 

Oops senior moment, thanks for the correction.