MC Forged piston wall clearance

I've got these .060" over MC Forged pistons that I'd like to use in my Atlas. The current barrel is already .040" over and in rough shape, so I think it would be a good contender. Does anyone have a feel for what the piston-wall clearance should be?

From: https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=30247

The MC forged pistons made/sold during the '60s-'70s era were good for their time. However due to the low silicon content alloy used 'back then' they expanded a lot when heated up. Because of this they needed to be fit very loose.

Also due to their design they would expand excessively on the sides across the pin boss area. Too late for many of us we found out in later years the piston skirt on the sides should be filed down a couple thou. aarrgh.

Also in that same thread:
MC Forged, made in the USA, is as good a piston as any and better than most (IMO). I have a set for the A10 for which the fol clearance data are given:
"Piston pin - .0005 to .0006 inch. "This is important on all forged pistons". [This is a "free fit"]
Piston [skirt] clearance - .003 for breakin .006 for racing."

And: I used them in my previous A65 race motor. They held up quite nicely. I used .004" of clearance at the skirt and Hepolite rings.

I had found that post. Do you think I can apply that to the norton?

Fritzer_108 said:

I had found that post. Do you think I can apply that to the norton?

Click to expand...

Metallurgy is as metallurgy does. I would think so because the liners are iron, and the pistons are made of the same material for all the air cooled motors mentioned. However, I've never held an MC forged piston or used one, and my logic may not be worth much. Maybe somebody that knows the pistons and has installed them in a Norton 750 will speak up.

Fritzer_108 said:

I had found that post. Do you think I can apply that to the norton?

Click to expand...

Similar technology, similar vintage, similar materials, similar displacements, similar requirements, similar performance expectations.. 1960's BSA A10 and A65 and Norton Atlas: each was a british parallel twin, 2 main bearing 360 degree cranks in each, each used cast iron cylinders with an alloy head, pushrod activated valves, air cooled, 2 valves per cylinder. Seems like what would be good for one would probably be good for the other. Biggest difference is that the Norton has a more modern combustion chamber, so doesn't need that huge lump on top of the piston to bump the compression ratio up.