My 455 Centurion was not running as well as it should be, so I checked the timing. It was way too advanced, but there's not enough room to retard the timing to the factory specs. The vacuum advance hits the heater bypass hose. Is the solution to take out the distributor and move it back a couple of teeth so that the vacuum advance is in a better spot?
Exactly. Be sure to line up the end of the distributor with the slot in the oil pump drive before you reinstall the distributor (takes a bit of "eyeing it"). Stop the engine at a known location (i.e. TDC-cyl 1), and move the distributor around. You have to move the rotor, cap, wires, etc. When you do it, remember that the rotor will have to point at the #1 spark plug wire, except now your vacuum cannister will be in a different spot. -Bob Cunningham
Carl, Are you saying you can't set your initial timing correctly? If so you have to reposition the distributor as suggested. If your total is too high, and it's a points distributor, check the advance stop bushing in the distributor.
Do you have the vacuum advance cannister sourced to manifold vacuum? And are perhaps shooting the timing with the vac advance line connected? If so, disconnect the vac line from the distributor, plug it with a golf tee or similar and shoot the timing again. That will give you an accurate read on the mechanical advance. Assuming as well that the engine idles slow enough (500-600 rpm) to read the initial timing setting.
It's the initial timing that was way too advanced. I was able to get it closer to where it should be, but it's still too far advanced by 6 degrees, and the vacuum canister on the distributor prevents it from going any further because it hits the bypass hose. I checked the initial timing with the vacuum line disconnected. I had a tough time at first finding the timing mark on the crankshaft with the timing light because it was so far advanced.
