OK guys... In researching some questions concerning IT pistons, I've come up with the following:

17.1.4.D.1.j - "Engines may be bored to a maximum of .040 inch over standard bore size. Factory oversize replacement pistons or their exact equivalent shall be used."

We can really stop there, and here is why...

"Engines may be bored to a maximum of .040 inch over standard bore size."

It doesn't say "shall", or "you have to"... it says you MAY...

"Factory oversize replacement pistons or their exact equivalent shall be used."

The "shall" MANDATES that you WILL, should you decide to overbore up to the allowed .040" over, use FACTORY or THEIR EXACT EQUIVALENT pistons... If factory pistons in .040" are not available, then this means you are out of luck in this department... You can only use an overbore that the factory supplies a piston for... PERIOD. That's exactly what the rule says...

Now, this is NOT affected by the allowance to obtain stock replacement parts from sources other than the manufacturer, because an overbored piston would NOT BE STOCK! It would NOT be a stock replacement part. That, again, is exactly what the rule says...



So, in my humble opinion, here is what I think:

1) You may bore your engine up to whatever size the factory supplies oversized pistons, up to the maximum of .040".

2) You may use either a FACTORY oversized piston, or it's exact equivalent... If the factory does NOT supply an oversized piston, or only supplies it up to .020", or .030", etc., then THAT is the maximum size you are allowed to use.

3) You may NOT have a .040" piston made if the factory does not supply one as well... If they do supply one, then you can make it's equivalent, but it must be an exact equivalent...

This is how the rules read. I see no allowance to create a .040" overbored motor in a case where the factory does not supply an oversized piston. Obviously, this means that not all car can take advantage of the full .040"... some may be limited to .020", .030", etc...

OK, fire away... show me where the holes are... I don't see any other way to read this... It is written...