For the first couple years of flying my KR I have been using a mild steel exhaust bolted to the original cast logs on the corvair. I had them ceramic coated and they have worked very well as far as keeping temps down in the cowling and had not cracked. Last year I tooled up and designed another exhaust using 4130, ceramic coated. It has the advantage of being much lighter than my first installation and cleaner. I have 100+ hours on it with no issues. The are currently available through aeromaxaviation.com. I believe that it is true that the life of the mild steel exhaust is better than the stainless. The ceramic coating is key to controling temperatures in the cowling and makes them look nice too.
Bill Clapp - KR2S builder and pilot Valdosta GA www.billclapp.com
