I have restored an Olmo with full Campy 8 speed (Ergos) drivetrain.
To ease the load on the wallet a little, instead of buying a Campy clincher wheelset I used a Shimano wheelset with a 7 speed 13-23 Shimano cassette, plus a 26 tooth 7-speed sprocket and spacer. AFAIK this should all work perfectly because the spacing (sprocket+spacer) of Shimano 7- and Campy 8-speed are the same, 5mm.
Everything works fine, apart for one thing. In the small chainring (39) the 4th sprocket skips. Above and below it, all is well.
I realised the FD was rubbing slightly on the chain (I hadn´t trimmed it properly, not used to Campy) and that got things a little better, but it still ain´t perfect.
So to recap, on the big ring all is well. Likewise, on the small ring - bar the skipping 19-tooth sprocket. The RD shifters smoothly in both directions and seems well aligned. The chain is the correct length.
Any ideas, anyone? I want to try and avoid making it any worse!
Here´s a pic taken before I put the chain and cassette on: