[KingJacobo]

My ignition timing was off a few months ago. Not adjusting the timing since I bought the car, naturally, I managed to screw up something simple.

Few months ago, I stuck an allen wrench into the distributor window and turned it until my timing was right. I recently fixed a massive vacuum leak, and it didn't idle perfectly. Not rough, but not quite where she needs to be.

Thinking maybe the timing/carb was off, I started with timing. Then it hit me my genius self didn't set the timing the correct way, I adjusted the timing curve!

The car had been running fine before the vacuum leak fix, but the timing was about 10 BTDC instead of 6 BTDC where the factory wants it to be (stock 66 Bonneville). I loosened the distributor hold down bolt, turned it a little, tightened the bolt and doubled checked the timing at idle.

She had tons of low end torque, but after about 35mph it kinda fell on its face. I needed to give it more throttle than it should have, and turned the car around to park back to the garage. I know I messed with the ignition advance which is probably responsible for why my powerband is all messed up. A friend of mine says I need to find the stock setting and set it to that.

Where do I find that?? I have the shop manual, but I don't think it's in there. Could I have a friend help me rev to 3000 rpm then adjust the advance curve accordingly to get the timing where it's supposed to be when it revs or am I way off?

[Deadhead]

You can set your dwell at first by using a matchbook cover as an initial gap. Then use a dwell meter to set.

The car will not run on factory timing setting. I don't really know where they got that from. Maybe it worked in 1966, but not today. Just advance it until it pings under hard acceleration and back off bit by bit until there is no longer valve noise. IMO you can squeeze the max out of it this way. I put a mark on the Dist shaft and on the hold-down with chalk or whatever to start with. When I know everything is right, and I have the max timing I can get in, I scribe a mark and work with that.

All this said, I don't know jack about a 389 with a Holley.

[giddygoat]

There are a number of items that determine timing, start with the Dwell first which is point gap, as Deadhead refers to. Hook up a Dwell meter and rev the engine, check to see if the dwell varys, if more than a degree or so there may be wear in the distributor bushings that should be checked. Set the dwell by adjusting point gap to spec, either by taking off the cap (Older points) or thru the window in the cap with allen wrench. Next check the timing marks and clean, unplug the vacuum line to the advance on the dist, start and set the timing to spec. Plug the vac advance back in and look for advance with the light, rev the motor to see the mechanical advance working. The three items that control advance are the points setting (Dwell), the vacuum advance(some can be adjusted thru the vacuum hose fitting or restriction in the vacuum line) and the mechanical advance under the rotor in the dist with different springs and stops. The balancer marks may not be correct if the rubber isolator has allowed the outside ring to slip. If the timing chain has jumped it will not be correct but engine may still run. To check for slip requires the number one piston be at Top Dead Center on compression, timing mark should be at TDC. When the timing chain jumps it is alittle harder to determine with out taking off the cover to look at the marks, if you know that the dist has not been turned you can pull the cap and set motor at TDC on number one and trace the number one wire to see if rotor is pointing to the number one connector with the cap on. It will not be right on but should be in the general area, but at best this is a guess, if the chain is loose or only jumped one or two teeth it is not going be determinable.
The point gap or Dwell and disb location set inital timing.
The vacuum advance compansates for throttle position based on vacuum.
The mechanical advance compansates for engine rpm and sets max advance.
They all work together to provide the spark at the correct time and changing one affects all the others. Heads, compression, fuel, engine load, cam, all have an effect on engine timing needs. Most set as stated and then back off the intital timing by turning the dist to compensate for knock from the high compression and low octane fuels as Deadhead refers to. It works to a point but there is a big loss in power running low octane fuels that the higher compression engines were not designed to use.