is lates 80s 8 speed Dura Ace compatable with new 8 speed HG cassette
 

well you already read the question so how about it? I have the derailleur and the shifters... I want to use the shifters with a modern MTB derailleur and an 8 speed cassette (touring bike) and I want to use the RD with 7 speed DT shifters and a hyperglide freewheel. What should I know?

Old Dura-ace stuff has a lot of compatibility issues with other Shimano. Late '80s may also be a Uniglide freehub, not Hyperglide. You haven't listed the specifics of anything you have so it's impossible to say whether it might work. What model shifters? What model/speed hub? What rear derailer?

7- and 8-speed Dura Ace shifters and deraillers have a different amount of cable pull, and aren't compabitle with other Shimano stuff. All other Shimano indexed rear deraillers have the same amount of cable-pull, including 9- and 10-speed Dura Ace. For example, you could match modern 10-speed Shimano bar-end shifters with a 105 rear derailler originally designed for 6-speed indexing, and use it on a 10-speed cassette. Shifters have speeds, deraillers don't.

Anyway, you can match your 8-speed D/A shifters with an 8-speed D/A rear derailler. This would work on any Shimano 8-speed cassette. But you can't use an 8-speed D/A shifter with any other Shimano rear derailler.

thanks. I assumed no one was going to reply... but I went to the Sheldon Brown link in the D/A barcon compatability thread. Since all 8 speed cassettes have the same spacing it should be no problem usuing these shifters with an 8 speed HG cassette. However, sheldon brown shows and alternate cable routing method which would allow me to use the 8-speed shifters with any other SIS derailleur and an 8 speed cassette. thanks for the replies.