When is it not recommended to use header wrap on cast iron exhaust manifolds on a turbo engine?
A. Cracking on stock exhaust manifolds and housing has never been a problem. Manifolds to the turbo can be a problem only if extensive modifications have been made to the castings. These types of castings have a high failure rate even without the wrap being applied to them. This is due to the uneven wall thickness of the castings from the machine work performed to improve flow of the manifold. The heat cycle generated could cause the cast iron to become brittle eventually causing cracking to occur.
