Timing or something else?

I need some help diagnosing a slight problem. I've got a 4 barrel Carter carb on an offenhauser manifold. I recently timed the engine and checked the dwell. Dwell was about 30, and the timing was set about 5 degrees BTDC. When I was setting the timing, it looked like the mark was bouncing around quite a bit. It definitely was not hitting exactly at 5 degrees btdc every time. When the motor is cold (as cold as north carolina gets in the middle of the summer!) I get a hiss out of the carb when I step on the gas and an occasional backfire out the muffler. It seems to go away almost completely when the engine warms up.

Is this normal? I was thinking the timing chain and gears may need changing. Any thoughts?

Thanks,

Milan
:v6:

 

timing bouncing around can be an indicator of worn bushings in the distributor or slack in your chain. I am changing the timing chain and gears in one right now. You can judge how much slack is in the chain by turning the crank by hand and watching the rotor turn. there should be little to no delay from when you turn the crankshaft, and when the rotor starts to turn. twost the crank first one direction, then the other and note how much slack there is. there should be virtually no play or free movement of the crank in relation to the rotor. 5 BTDC is a recommendation or starting point. dont be afraid to vary from that point. typically speaking, backfiring out the muffler equals late ignition timing. check the chain first and see where your at. BTW, the new NAPA on western Blvd extension ordered me a 3 piece set today for 23 bucks plus tax, and the gasket kit is another 11 bucks. will be here tomorrow at 8am and i plan on smelling fresh gas by noon. let me know if you need some help. Brannon