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The heads are 452's from Aero Head that have 2.14/1.81 valves. The heads were surfaced so probably close to stock cc. The short block is close to zero deck after going with L2355 flat tops.

Please define drone for me because I don't really know the term.



Its a resonance (think BUZZING) in the exhaust while your cruising at light-mid throttle. Often in the 40-60mph range.
Noise to the point of NO conversation in the car. VERY annoying.

3" pipes often contribute to it, and in my opinion 3" pipes connected to manifolds ASK for it.

My experience was brutal. Previous owner installed a 500W stereo to drown it out!!!