Google will be your friend for this. Mixing the two has been the 'holy grail' for many over the years. Especially tourers who have wanted the rear hub strength and cassette ratios of Shimano mtb kit with the feel and bar bag friendly nature of Campag ergo levers.
Solutions range from careful tuning of cable tension, to simple cable rerouting on the rear mech, through to little gizmos that alter the 'pull ratio'.
You will find lots of tables that list the pull distances of various shifters and the sprcket spacings on the different 5/ 6 / 7 / 8 / 9 /10 speed rear cassettes. When you have the details for the components you have, you will have some idea about how difficult it will to get them to match up.
Thanks Tim. So I take it the answer in short is, unless you're pretty nerdy about these things, probably best avoided, yes? (I really don't want to have to reroute cables or resort to gizmos - I'm just lookign for a cheap & easy solution: I have the Shimano 600 rear unit, there are some campagnoloa shifters on ebay I like the look of...I was hoping I'd be able to just fix 'em on & ride...but from your answer I suspect that ain't going to work, no?
Yes, in that case your probably better off buying something that is more easily matched up.
I think 8 speed Shimano is backwardly compatable with all 5 / 6 / 7 / 8 speed Shimano stuff, both mtb and road. If the shifters have more 'speeds' than your cassette, then you just ignore the unused 'clicks at the end of the range.
Hunting on eBay for this sort of stuff might be the way to go. Don't discount bar end shifters if you find some. 8 Speed barends were 'ultegra' quality and should be servicable for ages.
Eight speed STi levers were also still available new till last year and many shops will still have them in stock (NOS). They were the SORA model.
Thanks again Tim - much appreciated. Must admit I hadn't even considered bar end shifters...I've only ever used down tube ones, and am inherently suspicious of anything new fangled. I'll have a ponder & a poke around on ebay.
I've got 10 speed ergo shifters working with Shimano mechs and a shimano 8-speed cassette. Works perfectly, and I don't know why I didn't do it years ago. No gizmos, no cable re-routing; it just happens that the spacing of both systems is the same.
There's a list of combinations that work and don't work here.
Blimey. How old are they? How long is it since Campag were 7-speed??
I think you'll need to find out the sprocket spacing of the cassette or freewheel those levers were designed to work with. Then check the spacing of the casette you want to use it with.... or something.
I just took Chris Juden's word for it that it'd work. He's always right.