Quote Originally Posted by rspears View Post
If you look at the coefficient of expansion for steel and assume a nominal ten foot length for the pipes the movement from a 50F ambient to nominal 180F exhaust temp (higher with CAT's) yields over 1/4" of growth. It's proportional to the change in temperature, so going from a frigid winter day to operating temps is going to be more. Bob, you's will be flexing that vertical mount, and the donut provides very little for isolation with the bolt coupling both rigid parts.
Are you sure a 1/2"? The table I use, the expansion is given 10 to the negative 6th in inches. Coefficients of Linear Thermal Expansion