Interesting problem I've had with my '66 Barracuda since I modified the motor just a tad in 2001. When cruising with the windows down there is a strong exhaust fume odor that is quite overwhemling after I drive it steadily for around 40 minutes or more. But when my windows are up there is no odor at all getting into the interior!!! It doesn't matter if I keep the lower vent doors open or shut. Engine has a bigger cam, intake & Holley 600 double pumper and stock/original exhaust manifolds. Int. & Exh. manifold gaskets have less than 6000 miles on them. Any idea why the interior is sucking in all the fumes from the engine bay? Even working under the hood on the engine when its warmed up is bothersome. This really stops me from driving her on long cruises in the summer months.
Any insight fellas?????

MOPAR4LIFE, 273HYPO