[Dave at Pelican Parts]

You will have to cut the "head registers"--the areas where the cylinders go onto the heads. The OD of the 1.8 cylinder sealing area is lrager than that of the 1.7 ones, and they will not fit the 1.7 heads without making that cut.

You do recall that the 1.7 has smaller valves and a different combustion chamber design, yes? The 1.8 pistons will give you lower compression than the stock 1.7, but I'm not sure what the compression will be.

--DD