Well can't say I have seen that on a Rinker! I have a friend that has a Formula go fast with twin 454's with ss exhaust and has had nothing but problems! He has replaced the whole setup three times just for cracks and warpage. The manufacturer claims it is due to improper gaskets and torqueing of the bolts!
There is a setup procedure where you install the manifold, using the special gaskets, torque the bolts heat the engine up torque the bolts let the engine cool down heat it up and torque it again! Then check them every 25 hours or so!
