Matt-had this problem and fixed it with duct tape, but decided this wasn't an ideal solution :)

duct tape off
carb heat pull-on

carb heat push closed
duct tape on

makes for a messy check list

I replaced the knob with a push to lock knob similar to mixture control-they cost around AUD$250

I have the same problem with RAM air but live with it

Gerard


> Matt Reeves <mattreeves@yahoo.com> wrote:
>
> Fellow Lancairians,
>    
>   I have a strange problem and maybe some of you have had too.  This is
> for all the carb heat boys/girls.  
>    
>   I have the standard Lancair 320 air box.  At high airspeeds such as
> 200 mph or more, my carb heat will come out about 1/2 inch and the
> engine of course runs a little rougher.  I push it in, it comes back out
> all by itself.   So my fingers get tired holding it in.  (No jokes
> please).
>    
>   So, I think there is tons of air in the lower forward cowl that is
> counter-acting against my plate in the airbox that is trying to push it
> up and allow heat in.   I would think the straight shot intake would
> provide plenty of pressure to keep it down.
>    
>   I am wondering if anyone else had this problem OR if someone could
> send me a picture on how their cable is set up for the carb heat.   I do
> not have a push-rod type cable that I use on the throttle.  Maybe that
> is a possible solution.
>    
>   By the way, the fall colors in Upstate New York right now are amazing.
>  What a beautiful day of flying.
>    
>   Thanks!!!!
>    
>   Matt
>
>