I have a "survivor" '69 400/400 10.75:1, 330hp 4 barrel convertible. Exhaust system is original factory duals with muffler over axle. The car runs okay, but could be better. No evident mechanical issues i.e. smoke, stalling, knocking but acceleration is less than expected for the big cubes.

• Carb: 1999 professionally rebuilt QJ 7029268 WF
• Distributor: 1111946 with Accel recurve kit with heaviest springs, Crane adjustable vacuum advance
• Pertronix Ignitor 1181LSCC and unknown vintage Accel Super Stock coil, wires are new Delco 7mm and plugs are new Delco RapidFire
• Cam: 9779067 (273-289-54) .407" lift intake, .411" lift exhaust
• Head casting number isn't evident under all the power accessories, appears to say K16 (right head) and left head has heat riser shroud but has cast "DN" and "119288" just below valve cover Service manual calls it "Large Valve".
• Axle: Limited slip 2.78. Although I know this will reduce off the line performance, my previous 400 'Cuda with a 2.76 posi could turn ProTrac 50s over for 15 feet off the line, so on street tires the 'Bird should do better than chirp.

I installed the Pertronix Ignitor and made sure everything operated as before. Then new plugs, new wires, recurve kit and vacuum advance. Each thing one at a time, then road tested. The spark plugs provided the biggest performance increase, as the old ones were fouled and worn.

Engine idles best at 12 degrees initial timing but hot starts best at 8 degrees or less. Idle vacuum is 15" at 650 rpm, advancing timing increases vacuum but induces knock on acceleration at anything over 15 degrees. At 15 degrees it begins to kick back when starting. When I uncap manifold vacuum port and open it to the atmosphere the engine speeds up and runs smoothly.

I don't believe the engine has ever been opened for repairs. The valve seats are probably the originals and may have recessed. How can I check the valve seating without disassembly, and what should I look at to get some power out of this engine? I'm running premium unleaded 92 octane. Are there any preferred brands for performance cars? I'm not racing, or even street racing, but don't want to be afraid to put my foot down when some punk in a rice burner tries to pass on the right at an intersection.