Thanks, guys -- and I think the problem must lie inside the distributor. I replaced the cap and rotor, the wires are only a year old, and all the wires are attached to the correct plugs. My timing light is low-tech inductive, the same one I've used for years, and I removed and plugged the vacuum hose before checking the timing. The timing is actually advanced, not retarded, and I can't retard it down to TDC, much less 5 degrees BTDC. Any more thoughts?