I have a 1972 455 442 with what sounds like an exhaust leak that I'm having trouble diagnosing. It's definitely coming from the passenger side, so I replaced the exhaust manifold gasket(original exhaust manifolds, no headers), but that didn't fix the noise. Listening to it again, it seems like it's actually coming from the middle of the engine on the passenger side. If there is a leak in the intake manifold gasket around the exhaust crossover, can that typically be heard as an exhaust leak? I've never had the crossover leak on my cars; my exhaust leaks have always been in the exhaust manifold gasket(or the header gasket in the case of my '74 Camaro), or in the downpipe connection.

If I do have to take the intake manifold off, I might replace it with an aluminum manifold. Any thoughts about the W30 repo manifolds I see for sale at YearOne, etc.? As is, are they a good fit?

 

It's possible for the turkey tray to burn out at the crossover passage, but before pulling the intake check the hot air choke tubes. Not uncommon for the U in the crossover passage to burn out. Often manifests as an exhaust leak noise audible on passenger side.

To test- take the cold side fresh air tube out of the U tube, then start the engine and use a piece of fuel or vacuum hose as a stethoscope to listen around the choke tubes. You can also use the rubber hose to listen around the intake gasket.

 

Thanks, I had wondered about that, so Friday night I unbolted the u-tube assembly and pulled it out of the manifold. The tubes looked good, no holes that I could see. I used RTV on top of the old gasket(which was intact), and bolted it back in place. It still had the same noise.

 

The RTV will burn off, too hot there for that, they make some exhaust sealer in a tube which I like. I had a exhaust leak at the U Tube plate a while back, I had to order the correct gasket so I got 2 but still haven't needed the 2nd. Anyway using a piece of vacuum hose as a stethoscope as Rocket suggests is the best way. You will be able to tell exactly where the leak is, it will become one of your best tools. Try it.

 

To pin point an exhaust leak disconnect a manifold vacuum hose with the engine running. Put the end of the hose in about a half a cup of engine oil. Have an assistant plug the tailpipe with a wad of rags. The oil will cause the engine to smoke and the restriction caused by the rags will force the smoke out of the leak point(s).

 

Very interesting..... I dunno......