If there is no cam belt, then the cams won't turn with the crank, and you will end up with valves still protruding into piston space.
What does "CYL 1 at BTDC" mean? Do you mean TDC? (B = Before)
How does the RB26 rod compare in length to RB25 rods? Maybe the RB26 rods are too long, and are trying to push the piston crown into the combustion chamber.