Leaking Coolant
Those exhaust flange bolts are pretty tough. I thought my half inch impact would snap them right off on my 340. All it did was beat my hand to death with the wrench I had on the other side. Heat is your best bet if you can get some torches you'll be done in no time. Evan a propane torch will help. Dont break the exhaust manifold with that air chiesel. The bolts maybe tougher than the manifold.