if i set my timing to about 12* initial advance or anything around there it runs real crappy, backfires, and wont hardly rev. if i set it to about 20-25* it runs real good. i can't figure out why, could it be a timing tab or mark in the wrong place. the balancer and timimg cover are both stock though(as far as i know).

 

Could very easily be mismatched balancer and timing mark.

If you have the stock 305 balancer and one of those bolt-on timing tabs, then lining up the balancer mark with the 0° mark on the tab would put the timing at about 30-35° retarded.

Find TDC by looking in the #1 spark plug hole; compare that to the timing mark. Make a new one on the balancer that lines up with the tab if necessary, with white paint or a junkyard marker or something.

 

First, I'm not sure a 305 balancer is the right choice for a 283. Then again, if the rotating assembly was balanced at build time, it shouldn't be that far off on the inertia ring mass, even though the strokes and moment-center of the ring may be way different.

Second, you may have slipped the inertia ring on the balancer from high RPM shifts/launches that are common on the short-stroke engines. Tha would explain some apparent ignition retard (see below).

Next, old timing covers have had the marks in various places, and if you don't have the right balancer installed, you could be way off. As RB suggests, try to find TDC and make sure the marks are close.

Finally, if the base timing is off by that much, you may have skipped a timing chain or installed it a little retarded. One tooth on the cam sprocket is worth about 18° retard in cam timing. If this was done intentionally to support the short-stroke engine at higher RPM, it probably wasn't done properly, since 18° is usually way too much retard on most cam grinds. 6-10° is more common on those older 283s, 302s, and 327s that rev above 7,000 RPM. I know that these engines like a lot of ignition advance, but 25° sounds a little excessive, even for a really wild setup.

 

i think it could be what vader said about the inertia ring slipping. its not a balancer off a 305, the balancer and the timing cover are both stock from the 283 as far as i know. i'm probably going to get a new balancer anyways soon.

 

Actually, RB hinted at that first. An easy way to check to see if it is WAY off is to observe the mark in relation to the crank keyway. You'd have to remove the balancer bolt and washer, but should be able to see if it is within about 7° after the crank keyway. That's about the stock position on older SBCs.



It's gotta get you closer than 25°, and if nothing else will give you a good look at where TDC on the #1 cylinder should be, then you can reference the marks after that.

 

You may also notice in Vader's pic, the engine is of course at #1 TDC, and you can see the keyway exactly lines up with the #1 rod journal throw; so when the motor is at #1 TDC, the keyway points at exactly 1:30, 45° from straight up, i.e. exactly in line with the #1 cylinder. You can eyeball that within 5° easily if your 283 is like most of them and doesn't have its crank tapped for a bolt.

Notice also that the pic shows a timing tab for a 8" balancer, but the motor has a 6¾" one installed, which creates massive parallax error in trying to accurately set the timing. Typical of what happens with aftermarket timing covers. "I can't tell if my timing is within 10° or not - but just look at that shine!"

 

i found the problem. the outside of the balancer moves back and forth on the inside making the timing mark move about 1 inch.