coachman b 454

Had a Itasca for 11 years. Manifolds would last about 9 months. Replaced em 1 at a time B4 I was told the OEM's didn't have a GASKET. Bolted straight to the head. The only fix is to replace with headers & BEST gasket or to Buy the BEST, METAL aftermarket gaskets U can buy. Other Issues U WILL suffer... Hot Start problem, the starter motor gets too hot when stopped 4 a short time, like at a gas station. Its TOO close to U'r cracked(lol)manifold. Won't restart,about 45 min.)until it cools down. If U have the famous, belt driven Air pump thats s'posed to blow air into the exhaust to 'Reburn' gasses, REMOVE it. Easy to get shorter belt to fit. Plug off or just pinch off the air tubes going to each cylinder. When U remove the rite side manifold, check the exhaust pipe 'Butterfly' valve. Its probably stuck CLOSED. Remove it. Also, try advancing Timing to about -15 degrees or just B4 it starts to Ping. Much better HP. Install 3 or 4" DUEL exhaust!!!