Bore size for Speed Pro forged with Duroshield coating

[My427stang]

I hear ya...still don't like .0015, the PDF says .002-.0025, like almost double .001-.0015.
jus  sayin i know the growth will be in the block too, but i also know what a hunk of any aluminum does when you introduce heat, coating or not
the alum is still getting hot and growing at a different rate than the block, do i know more than the manufacturer....NO, but my pucker level is
telling me to ronald reagan it....trust but verify.
 

It's a minimum, so absolutely can go more, just saying that the coating is likely a thou at least when you measure both sides, and few times I have used those, the coating goes away after a while anyway. Not disagreeing with you at all just pointing out that it's my understanding that the coating isn't hostile to the wall

BTW way last time I used a set, they were loose, and worked fine

[WConley]

Correct.  The coating is for scuffing on initial break-in.  At Ford we did a few sets of coated zero-clearance pistons for a "world class" small car 4-cyl engine.  The block had a full bedplate and the crank was a nice forged fully counterweighted design. 

No issues with the way it ran, though the zero clearance wouldn't work in production.  That engine was hand built to a gnat's eyelash.  Man it sounded good and would happily rev to 8,000.  I'm sure it helped that the pistons had steel struts and were hypereutectic...

Of course it took another 20 years to get an engine that good into production, but that's another story!