I have a loud leak there somewhere but I can't even figure out how to get the pre-heater box off so that I can see. There is some sort of flap valve thing in the rear of the box. Is it likely that the exhaust manifold has a hole or crack in it? Thanks.
Dave
The shroud is held to the manifold by two nuts.
The manifold nuts/bolts are probably loose. They need to be checked occasionally for tightness(torqued). This is the most common fault. Also check the connection at the manifold to exhaust pipe. That donut gasket deteriorates over time. The studs/nut connection can come loose also.
Dave S(Texas)
Thanks. Do I have to remove both intake and exhaust manifolds at the same time? I have a big loud hole in there somewhere.
Dave,
These one piece 300 straight six manifolds, are the weakest thing about the
300-6.I have checked literally dozens of them in wrecking yards, never found a used one that wasn't warped. Bring a straight edge with you and you will see for yourself.
I have purchased a brand new one from Ford, one of the most expensive manifolds Ford sells, over $400... The newer fuel injected trucks ('92 anyway) fixed this problem by using two separate manifolds rather than one.
You can change the gasket, bolt it metal to metal without a gasket (mill the manifold, it will still be warped), but the only long term fix will be a new manifold. If it were me doing it again at this time, I would look into putting the newer shorter two piece manifolds on it...
Good Luck
If it were me doing this, I would look at Clifford Performance, which used to be Clifford Research and get a set of their spilt headers.
Whitelightning
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