Exhaust experts art the Aircraft Exhaust Company recommend a gradual installation. First, fit all the parts to the engine. Leave all the bolts loose, with just enough thread screwed in to hold the bolts in place. Now tighten the bolts gradually, alternating from bolt to bolt, until the correct torque is reached. Work around the engine. By bringing the torque up gradually, the parts will not warp or crack.
Work on a cold engine only. When metal heats up, it expands. When metal cools, it contracts. Suppose you remove a hot exhaust system. The engine is hot; it has slightly expanded. However, the new exhaust system is cold and may not even line up correctly due to the thermal expansion of the engine. Furthermore, using cold bolts in hot, expanded bolt holes will prevent you from torquing the bolts correctly. Save yourself a lot of headaches by working on a cold engine only. You will also avoid the risk of burns.
During the installation process, check for proper fit of all exhaust components, according to exhaust system fabricators at Acorn Welding. A recommended area to check for rubbing is the area below the muffler shroud. The muffler shroud can rub on the induction tubes at this point. Acorn experts also state that a part can sometimes be incorrect even though it has the right serial number. Since your airplane may have had several owners, its systems may have been modified from the original factory system.
As part of every pre-flight inspection, always check the integrity of your Cessna's exhaust system. This includes checking the exhaust bolts for proper torque. The bolts may work loose due to constant heating and cooling. Also visually inspect the exhaust manifolds and muffler for hairline cracks or any stress fatigue areas. If deficiencies are found, the damaged parts should be replaced.