8 to 10 degrees BTDC. / before top dead center. 10 May be to much. If it pings and rattles are is hard to start when HOT then slow the timing up alittle.
YES! Any time you adjust the timing you should disconnect the vacuum advance.
800rpm manual transmission, o degrees advance 1200rpm automatic transmission 4 degrees advance
Disconnect and plug the vacuum line and time the engine. Reconnet the vaccum and recheck the timing which should be advanced.
SBC timing should be set at about 6-8 degrees advance with the vacuum disconnected at idle, about 600-800 rpm
The vacuum canister can advance 24 degrees beyond initial timing.
Manifold vacuum usually. There may be some instances where someone reworked a distributor to arrive at a specific timing curve under load using ported vacuum with the vacuum advance, but this would be rare as most people would re-curve their distributor by changing advance weights and springs and would limit the advance built into a distributor so they could use more initial timing without having the total timing go over 36-40 degrees when the engine is revved up and all advance is in.
Which 454? The LS5 and LS6 are two VERY different engines even though they are both 454's. Timing specs are different as well. 8 degrees before TDC at idle will work for either, but may not be optimal.
There were not any timing belts in 1966. The timing should be set at 4 degrees before top dead center. With the base timing, the centrifical and vacuum advance all together should be 35 degrees.
just the top one that is the vacum advance, timing should be 2 degrees BTDC with vacum advance line removed and blocke
at cruising speeds you will be in a high vacuum situation that advances the timing for better economy.
That should be a 350 cubic inch engine with a carburator, HEI ignition with a vacuum advance. You will need to hook up a timing light to number one (1) cylinder. That is the front plug on the driver's side. Start the engine and let it warm up. There is an indicator on the front lower side of the engine. It is marked with the degrees. Disconnect the vacuum from the advance and plug it off and then adjust the timing to the desired specs. Tighten the distributor and plug in the advance. If you do not get an increase in rpm when the vacuum is connected, then the vacuum advance is bad.
Check your timing and your vacuum advance.