What I have are 452 heads with 2.14/1.81 valves, a pocket port and port matched on the exhaust side. The engine went 11.0 @ 119mph in my last Duster but I believe it was over-cammed. The headers are custom built 2 1/4" primary full length into a 3 inch exhaust that dumps in front of the rear tires. I can live with a nasty cam on the street as this car will be driven maybe once a week. Do to the loose converter and 3.91 gears I don't care about bottom end.
