Pelican Parts Forums - 2.2 bore & stroke to 3.0

Or even 2.9.

ANDIAL had a 2.9 kit (93mm Ps and Cs), which was used in SCCA where the 2.8 (92mm) was allowed with a 1mm overbore (that being a holdover from early days when you could keep a water cooled block in service longer with a succession of overbores - never made sense for 911s as a rule allowance, but it was there to be capitalized upon).

Furthermore, to go larger than 2.4 or 5, you need to bore the spigots of the 2.2 block larger.

In general, each successive generation of magnesium block was stronger than before. If you aren't going to use the sand cast early blocks, you want a 7R block. The best would be from a 2.4T, with the spigots bored out. The theory there is that those motors saw the least thermal and other stress, and thus have more life left in them than the 2.7s (came with the larger spigots to begin with, and had the most head stud pulling issues) or the higher horsepower 2.4S.

Which isn't to say you can't use your 1970 block. You just can't punch it out to 3.0 liters.

Unless you want to offset grind a 70.4 6 bolt crank for a longer stroke, and use a custom rod? But most of us racers seem to think we are better off with larger bores and, if stroke is changed at all to meet racing class rules, shorter strokes.