My engine sounds like the exhaust manifold is leaking. 1981 model, and doubt if it has ever been off the engine. Are there any sure test, and what causes exhaust gasket to go bad?<br />Temps are fine.
On those older 470's there is a rubber boot that attaches the exhaust manifold to the exhaust "shoe horn", those tend to go bad. Just age or overheating tends to wear down exhoust manifold gaskets.
