LA small block timing is suddenly way off

Waitaminut. Are you saying that your engine is a dual 4bbl?
-The dowel in the hole aint good enough. If you watch closely you will see the piston sit(dwell) at TDC for several degrees. This method isnt even good enough for your lawnmower. If you time a snomobile this way it will very likely burn up. While your mark may be correct, you havent proven it.Until you prove it we cant help you, cause the next step is even more critical of it being correct.
-The way you tell your story is very confusing.
-A circle has 360*. If you divide the circle into 8 equal parts, each part would be 45*. So if the rotor was 30* past the no 1 tower, then the ignition system might be firing into the next tower past the true #1 at full advance or it wouldnt run at all. I conclude therefore, that you are referring to the tower labeled on some caps as #1, and not to the actual wire that goes to the no 1 sparkplug. Depending on how you have dropped the dist. in, any tower could actually be no 1. But the only real no 1 is the tower with the wire that goes to no 1 sparkplug. Do you follow? Am I getting close?
-Some balancers have 4 strike marks, equally spaced around the perimeter (ie at 90*).These will help you set your valves, among other things. They are at 1/4 intervals.
- the clearing of the idle circuits is a delicate operation
-This next paragraph is for after you have proven TDC.
-Heres what I do.Starting with the engine at TDC #1 compression stroke.Take the cap off. Clock the distributor rotor so that it is pointing to, or very near to,the #1 cylinder(driverside front).The rotor doesnt absolutely have to be installed this way,it just makes it more likely that the true #1tower will be the one marked #1, and it makes the wires lay out nicer. Make sure the advance springs have properly parked the cam. If the rotor is not pointing there, the way to get it there is by removing the dist. and reclocking the oilpump driveshaft. This can be tricky. Take your time. Be absolutely certain when clocking the shaft to get it to drop down home, before you drop the dist. back in and all the way down. It may take several tries and the crankshaft may have to be rocked. A helper may be needed. Ok so thats done. Next we would clock the vacuum can to where it clears every thing, by pushing it all the way back to the fire wall. Since your dist. doesnt have a can,we will use the previously interfering mounting ear instead. Next rotate the crankshaft in reverse rotation to about 20* advanced.(If you cant see the mark that far up, heres what I do: with the crank at TDC mark the balancer adjacent to the 10* retarded line, then rotate the crank to align this mark to the 10* advance mark). Next advance the dist. to the point of firing the coil. I do this by popping the coil wire out of the cap and near-grounding it, and with the ignition sw on,rotate the dist.CCW, until it fires the coil. So, you heard or saw the spark ,right? Do it several times so you are sure. Now we just have to steer the spark towards #1 cylinder. Make a mark on the side of the dist.where the rotor is relative to the body.This is where the true no 1 tower must line up.Next drop the cap on, index it properly and secure it. Is there a tower that lines up with that mark? If yes, thats the tower to connect to #1 plug. If no, we may be in trouble. It needs to be within a few degrees. Its very rare that it doesnt line up. So next be sure to install all the other wires in the correct order. You are now ready to start it up and finalize the timings. As mentioned earlier some timing lights dont like the MSDs.If your balancer has no timing tape installed, you will need a dial-back type.So now the engine is running.Stabilize the idle rpm and check your idle timing. It should be very close to whatever you set it to during the set-up procedure( the 20*). Adjust as required. Now rev it up a little, if ok rev more until advance is all in. If no missfires then you are good to set the power timing. If it does missfire, we may have to re-phase the rotor. In the past I have taken a spare cap and drilled a 1/2 inch hole in the top, between the coil tower and the true #1 tower, such that when you shine the timing light in there on a running engine I could observe where the rotor was. If it gets too far off, it will crossfire.We will talk about re-phasing later if needed.