Engine still not right after timing set

A sticky valve will show up several other ways, besides a leakdown, namely ;
>If an intake;
At the end of the intake stroke, the piston may may push a lot of it's just-inducted A/F charge back up into the intake manifold, and on an undamped vacuum gauge you will see the pressure pulse . When the spark hits, I suppose, at low rpm, that fire may get up into the intake.Generally, as you rev it up, the misfires have a tendency to go away and the engine smooths out. Also, at low rpm, if you whack the throttle open, she will likely send fire thru the carb.

>If an exhaust valve;
during the power-stroke;
it will send fire into the headers. In shortys, it is possible for that fire to ignite unburned fuel exiting adjacent cylinders. The result is some popping in the pipes.
>on the intake stroke;
The pressure in the intake may be higher compared to what is in the headerpipe of the bad cylinder. So when the piston goes down on the intake stroke, the cylinder will tend to pull in exhaust, and so, not enough fresh A/F charge. It is possible for that cylinder to misfire, sending a portion or all of that charge into the header, where it can be ignited by fire from another cylinder. And, the exhaust is gonna both pop, and stink.

>Many times if you slow the engine right down,you can feel the piston intermittently sucking at the end of the tailpipe. If you have a cross-over, you will have to plug one of the pipes.
>>Not valve related;
If your headers are not properly sealed at the heads, then they will pull fresh air in, as part of the way they operate. Any unburned fuel in the headers is gonna "explode". This makes a lotta noise in the headers, and COULD make it seem like the engine is not running right. This is worst at low rpm/idle.