I'm in the middle of a rebuild of my A14 (still) and I've come across a problem. My original pistons have less than 1mm dish (60mm diameter dish approx). The most shallow dish I've been able to findin replacement pistons is 2.2mm, and they go up to 4.0mm. They are supposed to compensate for the dish depth by changing the pin height but the one set I've bought and returned had the same pin height (3 mm or so dish). So that would basically have resulted in a lower compression which I don't want.

So right now I've ordered the best I can find which is 2.2mm dish and the only overbore I can get is 1mm. Going 1mm over is pretty much the limit on the A14 right (meaning I'll never be able to overbore again)? Anyone know of any alternatives besides horribly expensive forged pistons? And at the same time can anyone explain the many dish depths available? They all say 8.5CR in the catalogs but there's no way the CR stays constant when the pin height doesn't change. Did the combustion chambers change a lot during the '79 model year and beyond? I'm confused.

And if I do go to custom pistons as a last resort could anyone tell me how high the CR would be if I go from ~1mm dish to flat pistons? Could I get by with mid grade gas (89 here in Dallas)? I have a feeling this is probably too complicated to answer right off the bat but hey it's worth a shot. I guess really if I do have to go with custom pistons a lot of dirty work will be involved in the design.

Is there a nice CR vs. Octane chart somewhere to use as a guide? I've looked all over the internet. (stock is 8.5CR, uses 87 octane fine here in TX, fairly low elevation).

Thanks for any and all advice!!!
michael