Years ago, 77, I used aluminum flex tubing after about 2 ft. of steel pipe coming off the exhaust manifolds back on my 69 charger. They melted after a 30 minute ride down the highway, after a few bursts of power, racing a 318 duster.

If your coming directly off the collectors, its going to hot. Probably hot enough to melt your system too, unless your using some higher grade aluminum with a higer melting point.