well ya you kinda have a half turbo but each component adds its contribution. Personally the crank is more important than the head as (and here we go this is just my opinion) Turbo plugs on a 12 engine provide a dubious contribution to power at best.
15's and 21's are another story
you can get by with stock head clerance on an MT (.018 thousanths) on 30 percent nitro yet above 85 degrees I recommend adding .003 (thats thousanths not MM) to get .021 MM head clearence. This will aid engine cooling.
PS always use a alumunium head shim against the liner if you can get one. If you have to add additional copper shims put them between the alumunium shim and the head button. Keep the alumunium one against the liner. This goes for 21's too
Last edited by Motorman; 03-27-2002 at 09:45 PM.