Any speedo cable ideas?

Ok guys, I have headers that I have welded cut-offs on to the collectors which are currently capped. When I go drag race I uncap them. Now the problem I have is the exhaust coming out of the header cut-off hits the speedo cable and has melted through the plastic cover (sheath) and it could damage it if I don't do something before I race again next Friday.

So what can I place over this 6in section of the speedo cable to protect it from the header high temp exhaust? Any siliconer stuff or plastics available. Thanks...........