I just read the rest of you post

I'm using an A12 in a Lotus 7A replica (Locost 7) that I'm building. I'll do no more that 3,000 miles a year, I train into NYC for work. So the cost of premium fuel won't be a factor. But here in the states we are currently paying $2.05 a US gallion (about 4 liters) for premiom and $1.85 for 89 octane.
That is why there are a lot of Big cars here in the US that get 8-11 miles a gallon.

I saw A12 flat tops on the net some where so I assumed I should be able to get A12a flat tops, and since they would be replacement pistons I thought they may make them a little oversized. I saw on e-bay stock A12a pistons + .02 inch just a day or so ago, tha twould make arround 1250 cc.

I just purchased a New Old Stock A12 a few days ago and am awaiting its' delivery.

Dog